$15° electronics toda - americanradiohistory.com · Today carries a range of electronics books...

AEROMODELLERS: SEE PAGE 24. $15°

electronics todaJULY 1979

Build Our: STAC Timer Light Triggered

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Enjoy reading about electronics? Choosefrom the informative Babani Series andorder using this card!Is electronics your interest? Then get into it more deeply in the speciar areas of your choice. ElectronicsToday carries a range of electronics books published by Babani Press and Bernards, amongst which arethose described below. (If someone has already used the card, write to Electronics Today Magazine, Unit 6,25 Overlea Blvd, Toronto, Ontario M4H 161)

IC 555 Projects Every so often a device appears that is so useful than one wonders how lifewent on before without it The 555 timer is such a device. It west irst manufactured by Signetics, but is now manufactured by almostevery semiconductor manufacturer and is inexpensive and very easilyobtainable Included in this book are Basic and General Circuits. Motor Car and ModelRailway Circuits. Alarms and Noise Makers as well as a section on the556.558 and 559 timers An invaluable addition to the library of all those interested in Electronics.

Price $4.30 including 300 postage and handling

52 Projects Using IC741 IC741 is one of the most popular, inexpensive and easily obtainabledevices available to the home constructor. It is also extremely versatile andcan be used in a great number of various applications This unique book, originally published in Germany. shows filly -twoOil ferent projects that can be simply constructed using only the IC741 and afew discrete components. An invaluable addition to the library of all those interested in electronics.

Puce $2 70 mcludIng 30C postage and handling

Mobile Discotheque Handbook The vast majority of people who stair up "Mobile Discos" know very littleabout their equipment or even what to buy. Many people have wasted a"small fortune" on poor, unnecessary or badly matched apparatus The aim of this book is to give you enough information to enable you tohave a better understanding of many aspects of "disco" gear The approach adopted is to assume the reader has no knowledge andstarts with the f undamentals, hopefully theexplanationsgiven are simplifiedenough for almost anyone to understand but please not that this is by nomeans the lull story The book is divided into six parts- - Basic Electricity. Audio. AncillaryEquipment, Cables and Plugs. Loudspeakers. Lighting Equipment and theinformation has been considerably sub -divided for quick and easyreferencePrice $4.80 including 300 postage and handling

28 Tested Transistor Projects Mr. Richard Tomos is a well experienced electronics developmentengineer and has designed. developed. built and tested the many useful andinteresting circuits included in this book. Some of the circultsare completely new and. to the best knowledge of theauthor, unlike anything previously published while others many bearsimilarity to more familiar designs.It The projects themselves can be split down into simpler building blocks,which are shown separated by boxes in the circuits for ease of description,and also to enable any reader who wishes to combine boxes from differentprojects to realise ideas of his own Most of the circuits are very economical on the use of components and inmany cases the semiconductors employed are non -critical, commonlyavailable and inexpensive types.

Price $3.15 including 300 postage and handling.

First Book of Transistor Equivalentsand Substitutes ShoWs alternatives and equivalents to many popular transistors made inGreat Britain. U.S.A., Europe, Japan and Hong Kong etc Companion Volume to BP14 - SECOND BOOK OF TRANSISTOREQUIVALENTS AND SUBSTITUTES An invaluable addition tothe library of all those interested in Electronics bethey amateur or professional.


Second Book of Transistor Equivalentsand Substitutes Shows alternatives and equivalents to many popular transistors made inGt. Britain. U.S.A., Europe. Japan and Hong Kong etc Companion Volume to BPI - FIRST BOOK OF TRANSISTOREQUIVALENTS AND SUBSTITUTES All invaluable addition to the library of all those interested in Electronicsbethey amateur or professional.

Price $ass including 30C postage and handling.

Radio Circuits Using IC'sB This book describes integrated circuits and now they can be employed inreceivers for the reception of either amplitude or frequency modulatedsignals. The chapter on amplitude modulated (a.m.) receivers will be of mostinterest to those who wish to receive distant stations at only moderate audioquality, whilst the chapter on frequency modulation (Cm.) receivers willappeal to those who desire high fidelity reception of local v.h.l. stationspossibly with stereo (and even quadrophony at some future date). Stereodecoder circuits and the devices available at present for quadrophoniccircuits are discussed. Voltage regulator devices are also covered becausethey are so convenient in all varicap tuned receivers and because they haveso many applications in all types of circuit Brian Dance is a highly experienced author who regularly contributes tomany of the popular electronic magazines that are available both in the U.K.and overseas. An extremely valuable addition to the libraryof all Electronicsenthusiasts.


50 (FET) Field Effect Transistor Projects Field effect transistors (F.E.T 's) find application in a wide variety ofcircuits. The projects described here include radiof requency amplifies andconverters, test equipment and receiver aids, tuners. receivers. mixers andtone controls, as well as various miscellaneous devices which are useful inthe home It will be found thatingeneraltheactualF E.T. used is notcritical and manysuitable types will perform satisfactorily. The F E.T. is a low -noise. high gaindevice with many uses. and the dual gate F. E.T. is 01 particular use for mixerand other applications. This book contains something of particular interest for every class ofenthusiast - shortwave listener, radio amateur. experimenter or audiodevotee A valuable addition to the library of all electronic enthusiasts.


Popular Electronic Projects Included in this book are a collection of the most popular types of protectswhich, we feel sure, will provide many designs to interest all electronicsenthusiasts All the circuits utilise modern, inexpensive and freely availablecomponents

The 27 projects selected cover every wide range and are divided into fourbasic areas. Radio Projects, Audio Projects, Household Projects and TestInstruments An interesting addition to the library of both the beginner and moreadvanced constructor


Electronic Music and Creative Tape Recording Electronic Music is the new music of the 20th Century It plays a large partin "Pop" and "Rock" music and, in fact. there is scarcely a group withoutsome sort of electronic synthesiser or other effects generator.

It is possible with relatively simple apparatus to create completecompositions using electronic and sometimes non -electronic musicalSOurCeS

This book sets out toshow how Electronic Music can be madeat home withthe simplest and most' nexpensive equipment. II describes how the soundsare generated and how these may be recorded to build up the finalcomposition With the constructor in mind, several ideas are given to enable a smallstudio lo be built including a mixer and various sound effect units.

Circuits are included for VCOs. VGA& Envelope Shapers, VCFs, Activeand Passive Mixers, Fuzz, Noise Generators, Metronomes and a 10 -NoteProgrammable Sequencer etc.

All the units shown have been successfully built and used by the authorand most of the projects can be built by the beginner. An unusual, fascinating and highly rewarding application of electronics.Price $4.50 including 306 postage and handling

IC LM3900 Projects The purpose of this book is to introduce the LM3900 to the Technician,Experimenter and Hobbyist. It provides the groundwork for both simpie andmore advanced usesand inconsiderable more than just acollection of emotecircuits or protects. The LM3900 is diflerent from conventional 'Op -Amps', it can be usod forvany of the usual applications as well as many newones. It is oneof themostersatile. inexpensive and freely available devices on the market today.

The book is divided into six basic sections -Introduction

Audio ApplicationsSimple Linear ApplicationsSimple Digital ApplicationsSignal Generator Circuits

Special Applications The LM3900 can do much more than is shown here - this is just anintroduction. Imagination is the only limitation with this useful device, butfirst the reader must know the basics and that is what this book is all about.


let Book of HI -Fl Loudspeaker Enclosures Contains 26 practical designs and over 40 drawings to enable theenthusiast to construct his own Hi-Fi Loudspeaker enclosures. Includes the following types of enclosures: -Corner Reflex. Bass Reflex, Exponential Horn, Folded Horn, Tuned cod.Klipschorn Labyrinth. Tuned Column, Loaded Port, MultispeekerPanoramic etc. Also covers general construction hints and embellishing of cabinets aswell as a considerable amount of other useful information. A must for the library of all audio enthusiasts.

Price $3.05 including 300 postage and handling

50 Simple L.E.D. Circuits The author of this book, Mr R.N. Soar, has compiled 50 interesting anduseful circuits and applications, covering many different branchee ofelectronics, using one of the most inexpensive and freely availablecomponents - the Light Emitting Diode IL E D ) Also includes circuits for the 707 Common Anode Display. A useful book for the library of both beginner and more advancedenthusiast alike. Companion volume to book No. BP36 - 50 CIRCUITS USINGGERMANIUM. SILICON 8 ZENER DIODES by the same author.


Handbook of IC Audio Preamplifier &Power Amplifier Construction Shows what audio IC's are, as well as how to use them. Includes practical constructional details of various IC and HybridIC/Transistor designs of about 250mW to 100W output This book is written by the very experienced and popular author Mr. F.G.Raver who deals with the subject in four parts:Part I Understanding Audio IC'sPart II Preamplifiers, Mixers and Tone ControlsPart III Power Amplifiers and SuppliesPart IV Hybrid Circuits An ideal book for both beginner and advanced enthusiast alike.Prigo $3 15 .ncluMro 30C postage and handling

50 Projects Using Relays SCR's & Triacs Relays. slIrcon controlled rect.liers (SCR's) and bi-directional triodes(TRIACs) have a wide range of applications in electronics today. These mayextend over the whole field Of motor control, dimming and heat control,delayed, timing and light sensitive circuits and include warning devices.various novelties, light modulators, priority indicators, excess voltagebreakers etc In this book. the very experienced and popular author - Mr. F.G. Rayer -has given tried and practical working circuits which should present theminimum of difficulty for the enthusiast to construct. In most circuits there is a wide latitude in component values and types,allowing easy modification of circuits or readyadaption of them toindividualneeds. An ideal book for both beginner and advanced enthusiast alike

50 Projects Using IC CA3130 The CA 3130 is currently one of the more advanced operational amplifiersthat isavailabletothe horneconstructor. Thismeans that it isotten capable ofa nigher level of performance than manyotherdevicesand that itoften needsfewer ancillary components In this book Mr. R.A. Penfold has designed and developed a number ofinteresting and usef ul projectswhich are divided intohvegeneral categories:I Audio ProjectsII R.F. ProjectsIII Test EquipmentIV Household ProjectsV Miscellaneous Projects An ideal book for both the beginner and more advanced enthusiast alike.

Price $3 15 including 30C postage and handling

Electronic Projects for Beginners In this book the newcomer to electromcs will find a wide range of easilymade projects, many complete with actual component and wiring layouts.Furthermore, a number of projects have been arranged so that they can beconstructed without any need for soldering and, thus. avoid the need for asoldering iron. This book which is written by theveryexpenenced author Mr. F.G.Rayer isdivided into four sections: -

1, "No Soldering" Projects2. Miscellaneous Devices3. Radio and Audio Frequency4 Power Supplies

An absolute 'must' for all beginners in electronics.Price $4.60 including 306 postage and handling.

50 CMOS IC Projects CMOS IC's a re probably the most versatile range of digital devicesforuseby the amateur enthusiast. They are suitable for an extraordinarily widerange of applications and are now also some of the most inexpensive andeasily available types of I.C. In this book Mr. R.A. Penfold has designed and developed a number ofinteresting and useful projects which are divided into four generalcategories:I MultivibratorsII Amplifiers and OscillatorsIII Trigger DevicesIV Special Devices An ideal book for both the beginner and more advanced enthusiasts alike.


Electronic Calculator Users Handbook An invaluable book for all calculator users whatever their age oroccupation, or whether they have the simplest or most sophisticated ofcalculators. Presents formulae, data, methods of calculation, conversion factors etc.with the calculator user especially in mind. often illustrated with simpleexamples.Includes The way to calculate, using only a simple four function calculator:Trigonometric functions (sin. cos, ten)Hyperbolic functions (sink, cosh. tank)Logarithms. square roots and powers. A comprehensive section of conversion factors covering such commonconversions as length, area, volume and weight etc. through to morespecialised conversions such as viscosity, illumination, and cargo shippingmeasures etc. Formulae and data for VAT, discounts and mark up, currency conversion,interest, solutions of equations, binary and octal numbers, areas andvolumes, statistics and mathematics etc.


See also pages: 11, 34, 55 for more publications from Babani, and also ETI.

Vol. 3. No. 7. JULY 1979Editor

STEVE BRAIDWOOD BScAssistant Editor

GRAHAM WIDEMAN BAScEditorial Assistant

JOHN VAN LIERDE

AdvertisingAdvertising Manager

MARK CZERWINSKI BAScAdvertising ServicesSHARON WILSON

Advertising RepresentativesJIM O'BRIEN

Eastern Canada JEAN SEGUIN &ASSOCIATES INC.601 Cote Vertu,

St. Laurent, Quebec H4L 1X8.Telephone (514) 748-6561.

Subscription DepartmentBEBE LALL

Accounts DepartmentSENGA HARRISONLayout and assembly

SARAH -JANE NEWMAN

Contributing EditorsWALLACE PARSONS (Audio)

BILL JOHNSON (Amateur Radio)JOHN GARNER (ShortWave Listening)

DICK CARTWRIGHT (Servicing )

EDITORIAL AND ADVERTISINGOFFICES

Unit 6, 25 Overlea Boulvard,Toronto, Ontario, M4H 1 B1Telephone (416) 423-3262

Published by Electronics TodayInternational (Canada) Ltd.

Printed by Livingstone Printing LtdDelta Web Graphics

News Stand DistributionGordon & Gotch, Toronto.

COPYRIGHTAll material is subject to worldwidecopyright protection. All reasonablecare is taken to ensure the accuracyof the information.

All ETI PCB Patterns are copyright .No company may sell boards to our

designs without our permission.

INTERNATIONAL EDITIONSElectronics Today International, 25-27

Oxford St.,London W1R 1RF U.K.Editor Ron Harris

Electronics Today InternationalRyrie House, 15 Boundary St.,

Rushcutters Bay, Sydney, Australia.Managing Editor Collyn Rivers.

Acting Editor Roger HarrisonElrad

Kommanditgesellschaft, BissendorferStrasse 8, 3000 Hannover 61 Germany

Editor Udo Wittig

Postal InformationSecond Class Mail registration number3955. Return postage guaranteed. Postoffice returns to Unit 6, 25 OverleaBld, Toronto, Ontario. M4H 1131

electronics todayinternational

INCORPORATING ELECTRONIC WORKSHOP

PROJECTSSTAC TIMER 15Today your home, tomorrow the world!TWO OCTAVE ORGAN 21Straightforward project to make musical instrument.LIGHT ACTIVATED TACHOMETER 24RPM measured for aeromodellers and industrial applications.

FEATURESPROPAGATION AND THE IONOSPHERE 28Radio waves: They fly through the air with the greatest of ease . . .

SURVEY OF VIDEO CASSETTE RECORDERS 35No need to personally "stay tuned" any more.REED SWITCHES 44If this conjures up visions of Moses in the rushes, then "read" on.BRAINS AND COMPUTERS 49Comparison of bio and semi technologies.OP AMPS 3 52More on these ubiquitous little devices.ELECTRONICS AND COWS 68Cows are now being surveyed by video.

NEWS &COLUMNSNEWS DIGEST 4AUDIO TODAYDown with hype.BINGO AND OHM'S LAW FOR CALCULATORS 56ETI Softspot: Under the N, 37k.IONOSPHERIC EFFECTS ON SHORTWAVE LISTENING 59Short Wave World looks at how the signals get to your set.A LOOK AT THE ETA 63Service News checks out this organization.QRM .65Helping hams.FUN OF ELECTRONICS .70The lighter side.

9

INFO & MISCELLANEOUSElectronics Paperbacks . . . .2, 11 More Circuits 55Tower's I. T S 11 Classified Ads 71

ETI Binders 12 ETI Project File 72ETI Subscriptions 20 ETI Marketplace 73Canadian Projects Book 34 Reader Service Info .74ETI Circuits No. 1 34 Advertisers' Index 74ETI T -Shirts 48

ETI CANADA-JULY 1979 3

NEWS DIGEST

FIRST MILLION -BIT MEMORY DEVICE- Magnetic bubbles store over a millionbits of data in this new memory component from Intel Magnetics of Santa Clara,California. Intel Magnetics is a subsidiary of Intel Corporation.

One -Megabit BubbleMemory

Intel Magnetics, a subsidiary of IntelCorporation, today announced theworld's first commercially availablemegabit (million -bit) memory device -the Intel® Magnetics 7110, a 1,048,576 -bit Magnetic Bubble Memory.

Intel Magnetics also introduced acomplete family of LSI support circuitsthat will enable system designers todesign bubble memory systems easilyand rapidly. With the supportcomponents, users of the megabitdevice can go immediately into systemdevelopment without becominginvolved in the intricacies of bubblememory technology.

A 128 -kilobyte system, with itssupport components, can be easilyconstructed on only 16 square inches ofboard space; and a megabyte memoryon only 90 square inches. These areonly fractions of the area required bysemiconductor memory devices.Moreover, error correction - whichnormally requires a separatesubsystem - is built into the family.

Along with extremely high storagedensity, the chief advantage of bubblememory is non -volatility. Like magnetic

cores, tapes and disks, bubblememories retain data when the power isturned off, while conventional semi-conductor read/write memories losedata.

The idea of using magnetic bubble toobtain very high density, non-volatilememory or logic elements wasintroduced in 1967 by Andrew Bobeckof Bell Telephone Laboratories.

The bubbles are small magneticdomains formed in thin, single -crystalfilms of synthetic garnet. The domainsare only a few microns in size and can bemoved by the creation of a magneticgradient across the film. Thedevice canbe controlled to perform memory orlogic functions. The presence of abubble at a particular locationcorresponds to a binary "1" and theabsence of a bubble corresponds to abinary "0".

Intel expects the component familyto be used in microcomputer applica-tions before it's used in large computerapplications. Immediate applicationsexist for high -density bubble memorysystems in microcomputers, while thearchitectures of large computers areexpected to go through an evolution inthe 1980's in order to utilize bubblememory.

Intel Magnetics will supply thecomponents family to equipmentmanufacturers. A prototype kit whichallows equipment designers to build amagnetic bubble memory system intonew products can be orderedimmediately. The price of the 7110prototype kit is approximately $2,000(for that price, it had better not leave abath tub ring. - Ed As. ). Deliveries willbegin this Fall.

Intel Magnetics, 3000 Oak meadVillage Drive, Santa Clara, California95051, Don Bryson (408) 987-7700.

CB Radio in BritainThere is still much argument

occurring in Britain as to whetherCitizens band radio should belegalised. James Bryant, President ofthe Citizens Band Association, recentlysent a letter to British Prime MinisterJames Callaghan urging him to takemeasures to legalise CB radio andpointed out what is considered by hisassociation to be a growing increase inthe illegal use of Citizens bandequipment in Britain.

Apparently, four UK manufacturers(not yet named) are already prepared tomanufacture CB sets if they should bedeclared legal. Bryant stated that theUnited Kingdom and Eire are the onlyEuropean countries which do not allowprivate citizens some form of radio-communication.

It has been said that if Britain adoptedthe US system this would lead toa floodof Japanese -manufactured equipmentinto the country. The Citizens BandAssociation have therefore pointed outthat every set sold could employmodern silicon chip technology fittedinto the set at the factory which wouldtransmit a unique identifying signal; itwould not be possible for a person tochange this set identifying signal with-out the resources of a microelectronicsfactory and the equipment could bemade so that it would not transmitwithout it.

Such a system would not onlyprevent Japanese sets from under-pricing the market, but would alsogreatly reduce the administration costsof the system whilst rendering criminaland antisocial use impractical.

Most countries use amplitude modul-ation in the 27 MHz band but theCitizens Band Association feel that thisis impractical in such a heavilypopulated country as Britain. Theysuggest that unused parts of the 220 to

4 ETI CANADA-JULY 1979

240 MHz band or frequencies of about900 MHz might be suitable, especiallyas only a relatively small bandwidth ofpossibly less than 1 MHz is needed.

The Association fear that if thenumber of illegal users of CBequipment continues to grow, theGovernment could be forced to adopt alegalised system similar to that used inAmerica and that thiswould preventthelater adoption of a better sytem. TheAssociation feels that Britain shouldlead the world into the adoption of aCitizens band system which enableseach transmission to be readilyidentified.

Nevertheless, there is still aconsiderable amount of feeling againstthe legalisation of this form of commun-ication in Britain.

From Brian Dancein the UK.

Solar PowerContracts worth a total of some $2.5

million for the development of newsolar heating equipment by 10Canadian firms were announced inQuebec City today by Pierre Bussieres,Parliamentary Secretary to the Ministerof Energy, Mines and Resources, onbehalf of Public Works Minister AndreOuellet.

Originally, over 15Q firmsfrom acrossthe country entered the competitionunder the federal government'sProgram of Assistance to SolarEquipment Manufacturers (PASEM),being administered by Public WorksCanada.

Mr. Bussieres said that the federalgovernment had not only committedsignificant resources to thedevelopment of a Canadian solarenergy industry, but had alsoundertaken equally importanttechnology transfer and publicinformation programs.

He indicated it is the government'sintention to pass on to architects,engineers, builders and developers ineach province the technological andfinancial results of pioneering effortswith solar heating, a renewable energysource which is inexhaustible, non-polluting, and available across thecountry, and more important, free ofprice increases.

Mr. Bussieres mentioned that the 10winning submissions were selectedfrom 42 entries after consideration by apanel of public and private sectorengineering and business specialists.The project range from the

development and production of newsolar panels to integrated solar heatingsystems.

Firms selected were AmherstRenewable Energies Ltd., Perth,Ontario, Electrohome Ltd., Kitchener,Ontario, Nortec Solar Industries Ltd.,Ottawa, Ontario. E.H. Price Ltd.,Winnipeg, Manitoba/St. Jerome,

Quebec, Solarsystems Industries Ltd.,Surrey, British Columbia, SolartronicsLtd., Smiths Falls, Ontario, SolathermEnergy Systems Ltd., Mississauga,Ontario, Temperature Specialties Ltd.,Downsview, Ontario, Thermo SolarInc., Montreal, Quebec, WatershedEnergy Systems Ltd., Toronto, Ontario.

The Amis MC 400 offers instant translation between three languages at a time and isbeing hailed as the world's first hand-held computer (well it sure beats pointing atthe menu).

Major Breakthrough In Consumer ElectronicsA hand-held computer that can

translate instantly between threelanguages at a time is being acclaimedas the development of the decade in theconsumer electronics field.

The Amis MC400 Translator, whichresembles an advanced calculator butwith a full alphabetical keyboard as wellas numbers, fits in the palm of the handand can translate words, phrases orcomplete sentences on bright -litdisplay according to the selection ofplug-in memory capsules.

The Amis enables a completelyunilingual person to communicateinstantly in any of the languagesprogrammed for the tiny unit.Conversely, any foreign word can beentered and the translation giveninstantly in the operator's nativetongue.

Capsules have been developed forEnglish, French, German, Italian,Spanish and Japanese, as well asphonetics, with Russian and otherscurrently under development.

To speed up communications, theAmis comes programmed with 50complete or partial phrases that can beaccessed and translated at the touch of

a button. Complete sentences can beentered on the keyboard either with orwithout these ready phrases.

Languages are carefully program-med on the capsules by specialists toavoid confusing a beginner withcomplicated tenses and conjugations.

Among the features of the Amis is areview of words with double meanings.The unit displays each meaning andthen translates the definition selected.It also corrects spelling errorsautomatically.

Languages actually are just the start.The Amis is really the first trulyportable, handheld computer capableof accepting any data for retrieval.Capsules are already underdevelopment for first -aid treatments,horoscopes, calorie counters, etc. andvery soon the Amis will be able to storeentire dictionaries and works ofreference, thus continually expandingits capability and literally putting thepower of a computer in the palm of yourhand.

For information please contact: PaulBerger, THE HOUSTON GROUP, 2015Peel Street, Suite 500, Montreal,Quebec H3A 1T8 (514) 288-8290.


NEWS DIGESTHot Stuff

New from Jana is a 30W solderingiron kit. The kit is totally self containedand comes with screwdrivers andtweezers to aid in assembly. We alsonoted this kit required no (thankgoodness) soldering in itsconstruction.

This would make a good beginnerskit, and shouldn't require more than anevening to build.

Price is approximately $ 10.00 fromJana Electronics, P.O. Box 489, Winni-peg, Manitoba R3C 2J3.

INSTRUCTION MANUALAn. 30W Soldering Iron Kit

UnderstandingFrequency Counters

With the increasing sophistication offrequency counter applications, suchas time domain stability measure-ments, engineers need better definedcounter specifications, as well as newspecifications.

In a new 34 -page application notefrom Hewlett-Packard, engineers andtechnicians are able to review basiccounter specifications as well asbecome acquainted with new specs.This new AN 200-4 entitledUnderstanding Frequency CounterSpecifications starts with a generalintroduction. Following is a sectiondetailing input characteristics ofcounters including range, sensitivity,signal operating range, dynamic rangeand trigger level considerations.

Operating mode specifications arecovered in Section III which includesvarious range specifications and adiscussion of least significant digit,resolution and accuracy.

Several appendices cover topicssuch as time interval averaging, rmsspecifications, effects of wideband

noise and measurement of courtercontributed noise.

Ask for AN 200-4, UnderstandingFrequency Counter Specifications,Publication No. 02-5952-7522.

Write to INQUIRIES MANAGER,Hewlett-Packard (Canada) Limited,6877 Goreway Drive, Mississauga,Ontario. L4V 1M8

D I P'ed BatteriesThese nickel cadmium battery

models in miniature dip -style packagesprovide reliable standby power inmicroprocessors and microelectronics. DS2SD-2 .4V 65 mah,DS3SD-3.6V 65 mah standard andDS2GT-2.4V 65 mah, DS3GT-3.6V 65mah gold top have continuousovercharge capabilities, polarity keyedterminals, and a flat discharge profile.

The gold top units are supposed toprovide longer life at elevatedtemperatures. From CGE they canwithstand high volume soldering tech-niques. For further informationcontact: Canadian General Electric Co.Limited Electronic ComponentsOperation 189 Dufferin Street Toronto,Ontario M6K 1Y9.

DMA ControllerIntel Corporation announces the

introduction of the 8237 and the 8237-2DMA controllers for use in 8085A and8088 microcomputer systems. Claimedto be the highest performance DMAcontroller chips available, these partsare designed to provide micro-computer peripherals a direct link tosystem memory, thus increasinginput/output (I/O) speeds andreducing central processing unit (CPU)overhead. The 8237 is specified at 3MHz, while the 8237-2 is specified at 5MHz. Both parts are pin equivalent tothe slower AMD 9517, 9517-1 and 9517-4.

In particular, the higher speed of the8237-2 allows it to be used with the8085A-2, the high-speed (5 MHz)version of Intel's 8 -bit microprocessor,and with the newly announced 5 -MHz8088 which contains the architecture ofIntel's high-performance 16 -bit 8086microprocessor, but preserves the 8-bitexternal bus structure.

The 100 -piece prices of the 8237 and8237-2 in plastic are $20.00 and $25.00respectively. The parts are alsoavailable in cerdip at 100 -piece pricesof $26.25 for the 8237; $32.85 for the8237-2.

INTEL CORPORATION, 3065Bowers Avenue, Santa Clara,California 95051, Mike Peak (408) 987-8080.

New AddressIcon told us to tell you their new

address, mark it on your calendar. IconElectronics Co., 333 McPhillips Street,Winnipeg, Manitoba, R3E 2K9.

The telephone number remains thesame - 284-1703.

Car Tape DeckAddition of a new AM/FM stereo

cassette car radio to the famousBlaupunkt line of car radios distributedthroughout Canada by Robert Bosch(Canada) Limited, has beenannounced by Alan Ingham, salesmanager of the Blaupunkt car radiodivision.

The "Essen" AM/FM stereo cassettecar radio from the Blaupunkt car radiodivision of Robert Bosch (Canada)Limited is claimed to have excellent FMsensitivity with clean, crisp audiooutput power. State of the art ICtechnology permits compact size (7" x5-1/4" x 1-3/4") - 177 x 133 x 44 mm)allowing installation in most import

vehicles.The cassette mechanism has locking

fast forward and rewind controls withmanual eject and power off eject.

The tuner/audio section featuresASU (Noise Suppression Circuitfor FMReception) and controls for volume

53 6 A 8 t

881 92 096 1100a a

AM

on/off, tone, balance, mono/stereoswitching and manual tuning.

Robert Bosch (Canada) Limited,6811 Century Avenue, Mississauga,Ontario, L5N 1R1 Phone: (416) 826-6060.


If you want morefunction generator for

the money,you'll have tobuild it yourself.

o

But first, lay down thatsoldering iron and considerthe following:

The Model 182 givesyou sine, square andtriangle waveforms, plustrigger and gate functions.Imagine getting tone burstsand pulse bursts out of anunder-$ 450 instrument !

What's more, the Model 182can be used as a sweeper.The sweep range (up to 1,000:1

WAVETEK

Model 182

or three decades) is con -Tolledby an external voltageapplied to the instrument.

For frequency range, you

get 0.002Hz to 2MHz, which isplenty broad for mostapplications.

1959

0EAR 1 OF

SERVICE

Allan CrawfordAssociates Ltd.

NEWS DIGESTTools 'n Instruments

Len Finkler announces some newproducts;

CONTINENTAL SPECIALTIES theMAX -550 pocket -sized 1KHZ to 550MHZ Counter. Max -550 is a high -precision, 6 -digit, audio -to -UHFcounter in a calculator -sized package.Employing the latest LSI techniques,MAX -550 provides precise, guaranteedreadings from 1000HZ to 550MHZ. Itactually eliminates separate audio, LF,HF, VHF and UHF counters - yet fits inpocket or toolbox!

The MAX -550 is fully automatic,requiring no adjustment of polarity,slope, trigger or input level. It can readto 100 Hz resolution with inputs as lowas 250 mV. Input is sampled for 0.1second, readout updates 6 times persecond.

And then there's the Hansen ModelAT -210; 100,000 ohms per voltmultimeter.

The model AT -210 is a handy type100K ohms per volt high sensitivityVOM designed for wide rangemeasuring and checking. With its solidmeter movement, high readable scale

and the other many excellentcharacteristics, accurate measuringand checking are available.

For further information, pleasecontact: Len Finkler Limited, 25 ToroRoad, Downsview, Ontario. M3J 2A6Phone - (416) 630-9103.

Atlas NewsNew from Atlas are the Milbank MIL'Series Two' line of Integrated PagingAmplifiers and Tuner/Amplifiers. Withthe MIL "Series Two" the followingchoices are available in ten differentmodels 25, 50 and 75 watts output, AMor FM Tuner on 50 or 75 watt models,110 VAC operation (or 12/24VDC-110VAC for MIL603MB), Each MIL"Series Two" Amplifier features,Attractive Styling, Solid State Design,Pre -Announcement Chime Capability.

Typical MIL "Series Two"applications will be offices, churches,schools, garages, taverns, restaurantsand factories.

Cobra, a leader in CB transcievershas just announced the introduction oftheir new 99GTL IN -DASH ENTER-TAINMENT CENTERS.

The 99GTL is the ultimate in theCobra Autosound programme, withfeatures like AM/FM/FM Stereo, StereoCassette Player, 5 AM/FM MemoryPushbuttons, 12 Watts RMS AudioPower per Channel, 1.8 uV Typical FMSensitivity, Speaker Balance Controlwith Center Detent, Front/Rear FaderControl, Graphic Equalizer/AmplifierAdaptability.

Atlas Electronics Limited, 50Wingold Avenue, Toronto, OntarioM6B 1P7 New Telephone (416) 789-7761.

Chroma RacksHammond Mfg. (Guelph, Ont.)

announces their new line of Chromasystem racks. Standard 19" panel widthracks come in 10 heights, each in 3depths, 17, 24, and 31". A wide range ofavailable options including panels,doors, turrets, blower systems,equipment chassis, drawers and more

'Tenna CatalogAn expanded catalogue featuring

Land Mobile antennas for commercialtwo-way communications systems isnow available from Cardon ImportCanada Ltd.

The catalogue highlights several newantenna models from Antenna Inc. forwhom Cardon is the exclusiveCanadian distributor.

Fully illustrated, the catalogueprovides reference material in an easy -to -read chart format. Included are lowband and high band VHF mobileantenna lines and UHF models. A rangeof mounting configurations are shownand described.

For a free copy of the new catalogue,write to Cardon Import Canada Ltd.,Box 937, Hamilton, Ontario.

DIP Switch CatAll important dimensions, circuitry,electrical characteristics, and materialsand finishes are illustrated or defined ina new catalogue of DIP switches fromGrayh ill. Request Catalogue No. 3 fromA. C. Simmonds & Sons Limited, 975Dillingham Road, Pickering, Ontario,L1W 3B2.

make Chroma racks unbeatable forequipment mounting versatility.Various door and panel stylings and awide range of standard finishes makeChroma racks compatible with anyenvironment. Chroma racks andaccessories can be seen in Hammond'snew 9R-8 catalogue and are availablenow through your local Hammonddistributor.

8 ET1 CANADA-JULY 1979

EVERY SO OFTEN, it seems to me, weshould stop talking and writing aboutaudio and start talking and writingabout audio instead. No, the typewriterhas not become stuck, and I hope theold professor is not coming unstuck.

We seem, at times, to become so pre-occupied with the hardware, and withthe technology behind it that we oftenlose sight of the purpose of it all. I knowI've dealt with this subject before, andwill probably return to it again, but thisseems to be necessary if we are to avoidwandering off into dead-end back-waters.

FUNDAMENTALREQUIREMENTS

Most treatments of High Fidelity andits basic requirements go on at greatlength about distortion, frequencyresponse, dynamic range, and all that,and end up with the admonition to letyour ears be the final judge. But no oneseems prepared to say what theyshould be the final judge of, and by whatcriteria this final judgement should bemade.

As a consequence, we find a rapidlygrowing market filled with all kinds ofgreat new wonder devices, all of whichconstitute "break-throughs","breaking down the final barrier" ofsomething or other, "revolutionary newdevelopments", and the like. Yet I cancount on one hand the number ofsystems I've heard which would matchthe sense of realism I experienced in1961, I believe it was, using a pair ofQuad Electrostatic speakers, Quad

AudioTodayDevelopments in audio reviewed by Wally Parsons

tube electronics, and one of the firstShure Stereo Dynetic pickup/armsystems. Or a direct -coupled tubeamplifier at an earlier time whosedegree of realism and transparencywas so stunning that the memory stillremains.

The first Stanton pickup I owned wasthe 681A. My first impression of it wasthe feeling of realism, particularlytransient attacks, and the shimmer ofstruck cymbals. Even on discs whichpresented tracking problems,particularly on inner grooves (it used aspherical stylus) this quality was stillthere. With many of today's discs withtheir high recording levels and highaccelerations it's hopelessly out-classed by other products, includingthat company's own successors, the 681EEES and 88 1S. Even so, very fewachieve thisquality of easy naturalness.

Perhaps recordings may be blamed,but here too, one hears all the evidenceof technical improvement, and yet thatelusive, indescribeable quality ofrealism is so often absent. Not long agowhile demonstrating speakers to arecording engineerfriend the subject ofdepth imaging, that is, front to backlocation, came up. One of therecordings I used involved diggingback 25 years to a now deleted Capitolrecording, in mono. This was recordedin one of Capitol's own studios by, Ibelieve, one of Capitol's staffengineers, back in the days when noadvertising or marketing managerwould have the gall to tell an engineerhow much he hated engineers because

they get in the way of the marketer'sschemes. Solo voice and orchestra, andthe solo voice stood solidly in front ofthe orchestra. Why and how this cameabout neither of us could explain. Manyof that same company's mono andstereo discs of twenty years agofeaturing the Stan Kenton orchestra,plus others which were an attempt torevive in modern sound some of the bigbands of the forties caught much of thisfeeling. Again, why, and how?

Much, if not most, of today'sequipment seems to be designed bythemarketing department, rather than bythe engineers. The marketing man

That young devil Jnkin i on bout 'owl. ing thmodulus of elasticity of air . I. h sending m up againSon7ll


Audio Today

decides what the public (i.e. dealers)want, not bothering to explain how thisknowledge was acquired in spite of thefact that the public doesn't know what itwants. The engineer is then ordered toproduce. The result is, not continuedresearch and development into ways ofproducing better equipment, but ratherinto ways of creating new fads andfashions, new "in" sounds and designphilosophies, fashions dictated bypeople with no knowledge of soundreproduction, and no real desire toacquire such knowledge.

"WITH IT" DESIGNPHILOSOPHY

I recently had a good look at thisphilosophy when I was approached bya marketing type who had gottennowhere with his present employers inhis attempt to produce a line ofspeakers with a particular "British"sound, but which was little more than acounterfeit version of a very popularAmerican design. This bright young ladquickly demonstrated a near -totalignorance of even the fundamentals ofloudspeaker operation and an evenmore total disdain for engineers andother design types. The propositionwould have involved my executing hisbrain -child, but not for the usual return,that is fee for service and a reasonablemark-up on each manufactured copy, ifI should engage in the manufacturing,but rather a partnership, or, failing that,I should expect to recover mydevelopment costs through a relativelysmall mark-up on the manufacturedcopies.

I was quickly made aware of thereason why I should drop my own trans-mission lines, including the kind ofcones materials which are acceptableto a certain market (one in which I haveno interest) heard all the old wives' talesabout horns and what's wrong withthem (somebody should tell Klipschand Electro-Voice; bet they'd besurprised), and so on and so forth.

There is such a thing as an"Underground Audio Movement"which, judging by what appears in theirvarious club publications, never listensto music, never pays consciousattention to natural sounds, andgenerally functions on the basis of whatRichard Heyser refers to as the "Catas-trophe Theory". It's too complex todescribe in a few words, but readersareurged to obtain the March, April, andMay issues of "Audio" magazine for afull dissertation, as well as T.S. Kuhn's"The Structure of ScientificRevolution" on which much of Heyser'sarticles is based.

SALES HYPEWhat it boils down to, for the purpose

of this discussion, is that a largesegment of the sales and marketingcommunity has fallen for its own saleshype, and set its criteria of performanceaccordingly. That wouldn't be so bad,except that the result is that so many ofthe perverted views which result havebeen rammed down the throats of manysegments of the audiophile publicwhen the latter have been at their leastinformed, and in the process set theseperverse standards forthat public. Aftera period of time, it becomes possible to"prove" that these are the standards towhich "people" subscribe andequipment which is built to thesestandards are what people want.

There's really nothing new in all this.It's a total plagiarism from theautomotive industry. During the fiftieseverybody wanted big cars with tail fins,and later they wanted big cars with lotsof chrome. Today, of course,everybody wants small energy-gfficient cars. Of course. The industryset us up by designing the kind of carsthey decided we should want, thenramming them down our throats. When'some people werecritical,they pleadedthat they were only giving the publicwhat it wanted.

It's all hype, of course, and probablycontributes more to energy waste thanpoor gas mileage.

RESPONSIBILITYIt has occurred to me from time to

time, that in writing this column I'massuming a large responsibility. I am, asare most other journalists, attemptingto provide leadership in setting thestandards of my readers. Even whendealing with "facts" these are always, ofnecessity, presented from theperspective of my own values.

The fact that so many readers appearto find my observations and oftenhighly opinionated views to bewelcome is most gratifying.

This column and the letters section isa forum for discussion. Yourobservations are welcome.

THE FOSGATE PUNCHOrdinarily this corner doesn't devote

much space to the subject ofautomotive sound or componentsthereof. The reason is simple: readerresponse suggests that more interestslie elsewhere. And, too, much of whathas been introduced to the market has,with few exceptions, been little morethan a joke when judged by high fidelitystandards. After all, what is one to thinkof an industry which regards 8 -track

tape cartridges as a high fidelity sourceof music programme, or brags aboutspecifications which would have beenan embarassment to the appliancemanufacturers only a few years ago. Orentices customers with brand or modelnames like "Mind Blower" or "MindBlaster".

However, during the past year or sothis area of audio has undergone amushrooming of development, with"legitimate" high fidelity manufact-urers getting into it, and newcomersappearing with equipment which layslegitimate claim to high fidelityperformance.

Typical of the latter, and in somerespects better than most, is the currentproduct line of automotive componentsby FOSGATE, dubbed "The Punch". Itwould be unfortunate if seriousaudiophiles were to lump product namein the same class as 'Mindblowers" andthe like, because it's an impressive linewith impressive specs, and, althoughI've not measured performance, I haveheard one of their systems installed,and can quite unreservedly describe itas the best automotive system I've everheard.

At present, the system consists offour preamp/amplifier combinations,the PR -220, with 20 W/Ch, the PR -250with 50 W/Ch, the PR -252 also with 50W/Ch with three band independenttone controls and output level indicator(LED), and the PR -2100, with four 50 Wamplifiers and built-in electroniccrossovers (variable). In addition thereare three speakers available, a 6" x 9"and a 5 1/4" long throw woofer, a 51/4"mid -range, and a 3" phenolic ringtweeter.

All electronic units claim a dampingfactor of 1000 or more, THD less than0.05%, frequency response from 20 Hzto kHz within 0.25 dB, and very low


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CONTENTS

CLASSES OP ENCLOSURESPHERE/IL TWEETER .PRODUCEREASE REELER HORNTUNE PORT BASS REFLEX ENCLOSURELIBRARY ENCLOSUREMINIATURE HORN LOADED REFLEX ENCLOSURE

ItARLSON ENCLOSURESEM FOLDED HMIWINO!. WALL BAFFLEBASS REFL. ENCLOSURE130 DEGREE BALANCED REPRODUCER 25CORNER FITTING LONG CHANNEL HORN ENCLOSURE 15LONG CHANNEL ENCLOSURE IS

HEAR LARGE HORN SLOT LOADED ENCLOSURE ISMINIATURE ENCLOSURE WITH IE. / 157 SPEAKERS ISROWEL SEALED CABINET ISREAR HORN REFLECTOR ENCLOSURE lboOLOLD HORN ENCLOSURE 17DISTMBUTED PORT ENCLOSURE 17Gum. AUDITORIUM ENCLOSURE IFU12010 TABLES I 13GENERAL CONSTRUCTION EDITS ISLNHELLNSHDRG SPEAKER ENCLOSURES IF

CRITICAL DAMPING ElCROW OVER RIMERS 21

PHASING LOODEPIAXERSQUADROPHONY 23FURTHER DEVELOPMENTS 24 STEREOPHONIC 24

QUASI -QUADROPHONIC 25DUMMY LOAD AND SPEAKER SISTICKING SYSTEM 21N1 -F1 COMPATABILITT PROBLEMS 30FREQUENCY RI -SPORES OF SOUND REPRODUCTION 34DECIBEL AND POWER RATIOS 34LOUDNESS LEVELS 3$FUNDAMENTAL FREQUENCY OF S01202 SOURCES 37

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Audio Today

T.I.M. distortion, attributed to the use ofa high speed (60 V/usec) in the circuit.

One curious characteristic whichconstitutes radical departure fromconventional techniques is thedescription of the tone controls whichclaim only to offer boost facilities,rather than boost -cut. I must admit thatat mid settings they appear to give levelresponse and indeed to act very muchlike conventional controls, withperhaps less cut than boost.

But at maximum boost it becomesobvious why the name "The Punch"was chosen. With the Fosgate speakersmounted as dual pairs in the rear parceldeck, and driven by the PR -2100 Bi-amp, full bass boost can give the feeling

of a giant fist punching the back of theseat. (incidentally, full boost at highlevels can drive even the 50Watt bi-amped system into clipping). Whetheror not you would like to drive along theroad with someone punching you in theback you'll have to decide foryourself (Iwouldn't), but the result is extremelyclean. Realistic, no, clean yes. Afterusing large transmission line speakersas a reference standard I find it difficultto get enthusiastic about the "realism"achieved by any 5-1/4" woofers, nomatter how many are used or what theirexcursion capabilities may be. But if wecan't have realism (and I have serious

reservations asto howachievable this isin an automotive environment) at least aclean, tight, peak -free bottom end, asmooth well projected mid -range, and asparkling top end are a most welcomealternative to having holes between theears.

Unavailable for examination wasFosgate's version of the TateDirectional. Enhancement System(DES) SO decoder, which is beingmarketed as the "Tetra -1", apparentlyusing the electronics of the PR -2100,and similarly the "Tetra -2"professional -cum -audiophile decoder.Apparently Dolby labs have acquiredthe rights for use of the Tate DES in thefilm industry, and may signal a

resurgance of interest in quadraphony.For more information contact Paul

Moores at Audio Dimensions, 198North Queen St., Toronto Ont. M9C 4Y1

LETTERSFirst, I would like to say that you have

made my subscription to ETI moreenjoyable and constructive. It isespecially interesting as of late becauseof your valued comments concerningTransmission Line (speaker) Systems.

A 4 -way TL System I am building willuse a Phillips AD 0211SO mid -range. Inyour July '78 Audio Today Productscolumn you mentioned two of its

shortcomings. Your cure for the cavityresonance is the basic reason for myletter. I would appreciate receiving yourrecipe for correcting this problem.

One question: why do you usefibreglass to fill the cavity and not longfibre wool? Is not long fibre wool thebest at damping?

D.F., Montreal, P.Q.

I'm glad you asked me that. Have youany idea how much fibreglass I havelying around the house?

Actually, one cannot legitimatelymake a blanket statement as to what is

In response to many requestfrom our readers we havearranged for binders to bemade so that you can keepETI's first volumes togetherand protected from damage.The binders are covered inattractive leather -look blackplastic and are designed tohold twelve issues. The ETIdesign is printed in goldletters on the spine.

The binders cost $6.00 each,which includes postage andPackaging. Do not send cash-you can pay by cheque, Master -charge, or Chargex . Credit cardorders must include your accountnumber, the expiry date, andyour signature. In all cases allowsix weeks for delivery- Sendyour order to ETI Binders,Unit 6, 25Overiea bld.,Toronto,Ontario M4H 1B1. Don't forgetto include your name and address.Ontario residents add 7% PSTor use the card oppositepage three.


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Audio Todaythe "best" material for damping. Muchdepends on the damping techniqueused (e.g. thermo-dynamic energyexchange, acoustic line resistance,etc.) and the frequency band involved.Thus, felt generally offers the bestperformance for surface treatment ofcabinet walls at mid and highfrequencies if the problem is primarilydue to reflections, but in this case (thePhillips unit) a cavity resonance is bestcontrolled by filling the cavity with amaterial which offers high acousticresistance at cavity resonance withoutdeveloping back pressure behind thedome. Acoustic fibreglass seems to fillthe bill.

In transmission lines I've beenexperimenting with various grades andtypes of glass fibre in conjunction withmy own unique method of linetermination, and some unusual sets ofdriver parameters. Unlike most TLSbuilders and manufacturers, I am notusing the KEF 8139 driver, which I

consider unsuitable for use in such asystem (and, incidentally, I'm no longerusing the Philips 12100). The type ofdriver in use at present features anextremely linear dual cloth suspensionand is capable of a 1"excursion with 10Watts input at resonance. I'm awaiting amodified version with a different motorsystem and voice coil material. Thereare some business problems involvedin getting commercial productionwhich are holding things up (Canadianbusinessmen really are a 'fraidy-catbunch), but the result of all this is asystem capable of reproducing pipeorgan and disco at live performancelevels with reasonable power, and thekind of bass impact which can causebreathing problems.

The stuffing of the line is not a simplematter of finding the "best" dampingmaterial, but of achieving theappropriate impedance match to theradiation impedance of the driver.

Getting the most suitable researchfacilities in this country is most difficult(I had set up a programme with anacoustic instructor at one of Ontario'sbetter institutions, but the governmentcut off funds for equipment, so that fellthrough. Thanks Pierre!), so, like somany of my readers, I'm doing it thehard way.

Another synthetic fibre of interest isspun polyester, available as Fortrel, andknown in the upholstery industry as"Fibrefill"which might be a trade -mark.It's used as the soft filler in quilts, etc.Long fibre wool is not that easy to get;mostly it's supplied to the mills inquantities absurdly large even forcommercial speaker manufacturing. I

Jensen Triaxial® 3 -Way SpeakersQuite simply. the most advanced car stereo speaker ever.

For the best sound ever in your car. The first car stereospeaker with a woofer, a tweeter and a midrange.

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suspect that its use in England was.influenced by the fact that theexperimenters were near sheep -raisingcountry and the material was easilyobtained. It has a tendency to settle,and when used in a speaker does nothold up well in shipping.

I understand that Phillips might beintroducing an open plate version of theAD 0211, in other words, a mid -rangeAD 1600 T, with some attention paid tothe cavity resonance problem.

A lot of readers seem to be experi-menting with TLS systems. How aboutwriting and describing your results andsharing some experience with eachother.

Not long ago I received a letter from areader thanking me for my reply to hisrequest for information on themodification of the Philips AD 0211, butadvising that the drawing andinstruction sheet to which I referredwas not included. In view of the fact thatI had sent out responses to a largenumber of such enquiries, it occurs tome that other readers may havereceived a reply with the relevant sheetsmissing. If so, my apologies, and pleasedrop me a line and I'll send them out. Ihave a nice pile of copies here.


ETI Project

STAC TimerThe most sophisticated timer project we have ever published, this unit is basedon the COPS STAC chip, giving it extraordinary versatility.

THE NAME OF this project is derivedfrom that given by the manufacturerto the IC around which it is built.STAC stands for Standard Timer AndController and the device is part ofNational's COPS (CalculatorOrientated Processor System) group,a series of what are, in effect, dedicatedmicroprocessors.

The STAC provides a 24 -hour clockwith four digit display, much as anyclock IC, but has four control outputswhich may be programmed to turn on,turn off, or to retain their currentstatus at any one of four preset timesduring the day. STAC also has thefacility to "skip" certain selected dayswithin its seven or eight day (selectable)cycle.

The IC is thus a perfect basis formany control applications from airconditioning installations to fish tanksand hi-fi systems. The STAC's outputsoperate four relays with normally opencontacts, which can switch 120 voltsat up to five amps.

A row of LEDs below the readout

shows the condition of the outputs, andis also useful for checking a program.PROGRAMMINGSetting up the STAC is quite straight-forward and rather like using a program-mable calculator. At switch -on the clockis set to 0000, all set points are zero andall outputs are off, all days are validwith the present day set to one. Thedisplay will show the clock output.

Setting the clock follows the usualprocedure adapted with any digitalclock. Pressing SET HOURS or SETMINUTES will advance the digits ata rate of four per second.

To enter the program mode theDATA ENTRY key is pressed momen-tarily. Upon activation, the first setprogrammed. After setting four programpoint time will be displayed, and itsoutput status will be shown by thedecimal points of the display. To setthe time of an operation, the SETHOURS and SET MINUTES keys areoperated until the desired time isdisplayed on the readout.

If it is desired to switch an output

STAC Timer

on at tlis time, the SET STATUS keyis pressed to light up the decimal pointcorresponding to the output. Eachtime the key is pressed the decimalpoint will move one place to the right.If a combination of outputs is requiredat this time, the HOLD STATUS keyis used to hold the decimal point on,before moving on with the SETSTATUS key to the next decimal pointrequired to be on. Using the SETSTATUS and HOLD STATUS keys, anycombination of the outputs can beset up.

If an error is made in programming,using the SET STATUS key from thefourth point will clear all data and theproper information can be re-entered.

So far we have only programmed oneof the four set point times. By pressingthe ADVANCE SET POINT key thedisplay will go to 0000, can again beset to a time, and the output conditionsset up. Once this has been done fourtimes, pressing ADVANCE SET POINTwill return to the first set point time.

Programming can be verified by using


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ETI Project

* 3 2

4

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143

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P12

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C 41=1 .4 R1 ). .4 R3

CONTROL OUTPUTSTO RELAY BOARD

U R

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ST.,. LINK 1

6 1C4

*dp 9 d 7 a

-TO DISPLAY BOARD-

NOTE: DO NOT INSTALL LINK 1FOR 60 CYCLE USE

e LED 2 LED 3 LED 4LED 21

A CB I D e P 1 g

DISPLAY

Fig. 2. Component overlay of the main pcb.

A4A3 AZ Al

I :34-

0 2

+ 16V D1""-11:3-'

GND(CT)

Ti

X V W

Nate; If suitable miniature transformercannot be obtained use chassis mounttype and omit corner of pcb if desired.


- STAC Timer

OV

OUTPUT

INPUT J +16V

Fig. 3. Component overlay for example relay board.

PARTS LIRESISTORS all ',W 5%

Al 470kR2 100kR3 150kR4 47kR5 5k6R6 56kR7 100kR8, 10, 12, 14,16, 18, 20, 22 . . 15kR9, 11, 13, 15,17, 19, 21, 23 . . 4711R24 - R27 . . .1k

CAPACITORSC1 10n greencapC2 1000o 25 VW electroC3 100o 16 VW electroC4, 5 100n greencapC6, 7 4,17 16 VW electro

SEMICONDUCTORSICI MM57160 STAC IC

(National)IC2 4001BIC3 LM340T-8.0IC4, 5 4050BIC6 400113 2N2222HQ1 2N2222A similarQ2 2N3905 or similarD1, 2 1N4001 or similarD3,4 1N914LED1 - LED4 red light emitting

diode

DisplayCommon cathodemultiplexed displayssuch as nationalNSB5881

SWITCHESPBI - PB8 miniature momentary

push button switchesSW1 SPDT min. toggle

MISCELLANEOUSpiezo electric alarm such as Projects ,

Unlimited A1400 case to suit . displayfilter, nylon terminal strip, molex pins,28 pin IC socket or molex pins, nuts,bolts, etc.

TRANSFORMERTi ]20V/24ct @ 200mA

Parts For Relay BoardR28 - R31 . . . .10k Y.W 5%R32 - R35 . . . .4k7 YON 5%Q3 - Q10 2N2222AD4 - D7 1 N914R L1 - RL4 . . . mini PC heavy duty

12V relayPCBs for this project: check withSpectrum Electronics, 38 AudubonSt. S., Hamilton Ont L8J 1J7 andB&R Electronics, P.O. Box 6326FHamilton Ont L9C 6L9. The MM57160can be supplied by Northern BearElectronics, P.O.Box 7260 Saskatoon,Sask. S7K 4J2.


New Sindair DM235digital multimeter.

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Sinclair DM235 offers the most important features in a bench -topmeter in a rugged yet lightweight instrument for true portability!High basic accuracy (0.5°A3 2VDC range), high resolution (8mmLEDs), high input impedance (10 megohm) means superiorperformance at a price lower than any competitive makes. Specialoffer valid till August 31/79 at participating distributors. See ittoday!

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SINCLAIR DMM's AVAILABLE IN:MONTREAL -Addison TV, Microtron, Vision tronique. TORONTO -A-1 Electronics,Arkon, Dominion Radio, Duncan Instr.. General Electronics. Gladstone Electronics. MISSISSAUGA - Atwater.LONDON - Provincial Electronics. OTTAWA - Kris Electronics, Wackid Radio. WATERLOO - Waterloo Electronics.KITCHENER - Orion Electronics. HAMILTON - Canadian Admiral. GUELPH - Neutron Electronics.

Dealer/distributor enquiries welcome. AUDIEX ELECTRONICS, 1736 Avenue Rd., Toronto (416) 787-7367.

NEW IAOlta"cordlesssoldering ironcompletely rechargesin 60 minutes.MAKES CORDLESS SOLDERINGPRACTICAL FORHEAVY -USE APPLICATIONS.

The Iso-Tip 60 can make up to125 electronic joints or moreper charge. When completelydischarged, the iron can berecharged and used in a fewminutes or fully recharged inan hour. Low voltage, batterypowered, ground free isolatedtip design.

WAHL CLIPPER CORPORATIONORIGINATORS OF PRACTICAL CORDLESS SOLDERING

I

16 snap -intips to fitany job

plus aPC Drill.

1

See your Electronics Distributor, or write for Free Lenline Catalogue.

len finkler limited 25 Toro Road, Downsview, Ontario M3J 2A6Telephone (4161 630-9103 Telex 065-24010

STAC Timer

SUBSCRIPE

TIONS$14 / year (12 issues), $26 / 2 years(24 issues), for U.S. please add $3/year, other countries $5 / year.

To get a subscription to ElectronicsToday you can use the subscriptioncard, but if someone's taken it alreadydo the following:

Send a cheque, money order, Chargex,or Master Charge information, toELECTRONICS TODAY Magazine,Unit 6, 25 Overlea Blvd., Toronto,Ontario, M4H 1B1.


ETI Project Two Octave Organ

Two Octave OrganAlthough cheap and simple to build, this monophonic electronic organ is tunable,covers a full two octave range, and has an adjustable tremolo control.

HERE'S A PROJECT where you canwell and truly utilise your ingenuity!

A monophonic organ is limited inits scope simply in that only one notecan be played at a time - that is youcannot play chords. In practice this isnot as big a limitation as it might seemand a monophonic organ of this typewill provide a great deal of pleasure andamusement for youngsters and olderpeople who quickly find how easy it isto play.

The organ covers the range from C(262 Hz) to C (1047 Hz), with 12 notesper octave (that is it includes sharps andflats).

The frequency (pitch) of each note isdetermined by an associated resistor inthe chain R8 through R31. We havemade some minor compromises in thatwe have used standard readily availableresistor values nearest to those actuallyrequired to obtain the exact pitch foreach note. The pitch errors are quitesmall but if you need the pitch to beexact all you need to do is to wireadditional resistors in series or parallelwith the appropriate chain resistor untilthe exact pitch of that note is obtained.

The overall pitch is adjusted bypotentiometer RV1 and the volume bypotentiometer RV2. Tremolo may beswitched in or out by switch SW1. Thedepth of tremolo may be altered bychanging resistor R2.

As shown in our main circuit drawingand component overlays the circuit in-cludes two output transistors (Q1 andQ2) and a loudspeaker. This enables theunit to be totally self-contained. Never-theless it has been so designed that youcan run into any other suitableamplifier or hi-fi system. If you wish touse an external system as suggestedabove simply leave out 01 and Q2,change C6 to 1.0µF, and increase RV2to 10 k. The positive end of C6 shouldbe connected directly to pin 3 of 1C2and the input to the amplifier or hi-fi

system taken from the point on RV2which is currently wired to the speaker.

CONSTRUCTIONThe organ consists of two mainassemblies, plus a battery or other ninevolt power supply, and a loudspeaker.

Main board construction is quitestraightforward - the usual precautionsmust be taken to ensure critical com-ponents are inserted the right wayround and do check for solder bridges,particularly if you are using the Vero -board method of construction.

The second assembly is the key-board. Here you have unlimitedpotential for modification. We haveshown what we believe to be the cheap-est possible construction - 25 pinsstuck into a piece of heavy cardboard!But if you want to, you can build up afar more elaborate affair using propermetal or woodworking techniques.

The requirements for the keyboardare very basic. You need to arrange

some way by which one common wiremay be caused to touch any one of aseries of contacts. Our prototype showsa very basic way indeed. We have aseries of drawing pins stuck into a pieceof heavy cardboard with a keyboardpattern drawn on. The common wire isconnected to a sharp probe and yousimply touch the drawing pin headswith this probe. If this basic method isused a suitable probe can be made byepoxying a needle into the end of anold ball point pen. Note that the probehandle must be insulated to prevent60 Hz mains voltage included in one'sbody modulating the pitch. A moreelaborate way would be for each key tobe sprung in such a fashion that whendepressed it touched a common striprunning right along the front of thekeyboard. If you have the facilities forso doing, yet another way is to etch akeyboard on a strip of pc boardmaterial.


C-3

C1

1n0

Circ

uit d

iagr

am o

f com

plet

e un

it.

WIL

Firs

tly c

onsi

der

IC2.

Thi

s is

a 55

5os

cilla

tor

circ

uit w

hich

osc

illat

es a

ta

freq

uenc

y de

term

ined

by

wha

teve

rre

sist

orin

the

chai

n R

8 to

R31

is

sele

cted

. The

se r

esis

tors

hav

e be

ense

lect

ed to

giv

e th

e cl

oses

t pos

sibl

eap

prox

imat

ion

toth

est

anda

rdsp

acin

gbe

twee

nno

tes.

The

se

Oth

erre

sist

ors

may

be

adde

din

C.)

HO

W IT

WO

RK

S

serie

s or

para

llel

ifan

exa

ct s

cale

is r

equi

red.

The

out

put o

fIC

2is

appr

oxi-

mat

ely

asq

uare

wav

e.T

his

isbu

ffere

dby

01an

d 02

bef

ore

driv

ing

the

loud

spea

ker.

The

con

trol

circ

uitr

yis

deco

uple

d by

R7/

C3

from

the

nine

vol

t sup

ply

to p

reve

ntlo

adflu

ctua

tions

vary

ing

pitc

h.P

oten

tiom

eter

RV

1 ad

just

s th

e ov

er -

/WV

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710

0 01T

IP29

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Q2

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*-01

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0V

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210

0

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m cD

all

freq

uenc

yof

the

circ

uit

thus

actin

g as

a p

itch

cont

rol.

Tre

mol

ois

gene

rate

d by

IC1.

Thi

s IC

osc

illat

es a

t eith

er 5

Hz

or5

kHz

depe

ndin

g on

the

posi

tion

ofS

W1.

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n sw

itche

d to

the

5 H

zpo

sitio

n th

e ou

tput

is a

pplie

d to

pin

5 of

IC2

thus

mod

ulat

ing

the

outp

utof

that

IC. C

apac

itor

C4

'kill

s' th

e

outp

ut w

hen

IC1

is s

witc

hed

to th

e5

kHz

posi

tion.

The

rea

son

for

this

appa

rent

anom

aly

isth

atit

is

desi

rabl

e fo

rth

e tr

emol

o os

cilla

tor

to b

e ru

nnin

g at

all

times

- w

heth

ertr

emol

o is

switc

hed

inor

not

- to

elim

inat

e th

e m

inor

cha

nge

in o

ver-

all

pitc

hot

herw

ise

caus

ed b

y th

elo

ad o

fIC

Ibe

ing

switc

hed

on .o

rof

f.

Two Octave OrganWhen completed, the chain of

resistors should be soldered in place.Do make sure you have good soundsoldered joints as the failure of any onejoint in this chain will prevent theorgan from operating.

Finally connect the two assembliestogether, connect up a battery and awayyou go!

Some refinements may be made it is

TO SW1

4-

possible to delete the trim potentio-meters currently shown located on thecircuit board, replacing these with largerrotary potentiometers located remotely.

Resistor R2 may be changed to varythe depth of tremolo or replaced by a

potentiometer (10 k in series with a3k3 resistor) to allow immediateadjustment.,

crcc

110 0 V

404N TO SPEAKER

cr

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Component overlay for printed circuit board version.

TO -1 C2 ASW1-

A

CDEF

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B

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J

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Overlay for Veroboard version.

For pcbs for this project contact B&RElectronics, P. 0. Box 6326F, HamiltonOnt. L9C 6L9, and Spectrum Electronics38 Audubon St S, Hamilton Ont, L8J1J7. A complete kit of pcb plus partsis available from Northern Bear Elec-tronics, P.O. Box 7260, Saskatoon,Sask., S7K 4J2.

13

ITO KEYBOARD

46_(1._\/

RV2TO

SPEAKER

Of-NMTrulWr.-COMOI-NCIV'MWNWM0,-NM.ItnCONWC70.-Nel.-NM,:j.OWNWM NNNNNNNNNNMMMMMMMMMMVVV50 0 0. 0 0 00 0 o 0 o o 0 o 0' o )0000000000004,0000000000o a9 GO oo 0 0 0 I I. 0° 0o 0 0 a aO

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Printed circuit board layout -- shown he,e full

size PARTS LIST

+9V

RESISTORSR1R2R3R4R5

R6R7R8 -R11R12 -R14R15

R16R17R18R19 -R20R21

R22 -R23R24R25 -R28R29 -R31

RV1RV2

CC1PACITORSA

C2C3C4C5C6

IC1/1C201Q2

68k % W 5%8k22k26k88k2

10k100 ohms2k72k21k8

2k21 k51k81k51k2

1k51k21k820

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SI Ft

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IF

VI

Trimpot 5k" 100 ohm

1 n0 polyester1 uF electrolytic 16 V220 uF "

100 uF56 n polyester100 uF 16 V electrolytic

integrated circuits 555transistor TIP29Ctransistor T I P30C

Printed circuit board ETI 072 orVeroboardSW1 single pole switchNine volt battery and clipSmall speaker

Drilling details for Veroboard.


ETI Project

LightActivatedTachoThis tachometer measures rotational speed without physical contact,by picking up reflected light.

THE USE OF a non -contact method ofmeasuring RPM is not only convenientbut sometimes the only methodSome motors used for model aircrafthave a capacity of only 0.15cc yet runat speeds in the 25000 RPM region. Thepower required to turn a mechanicaltacho would be many times the powerof such a motor. Also on some machinesthere is no convenient place a normaltacho can be fitted.

DESIGN FEATURES

As the main application for this unitwas to be outdoors it was decided thatan LCD display would be preferable toan LED and more easy to read than ananalogue meter. Unfortunately LCDsare not yet readily available, and norare the ICs needed to drive them.

However the Intersil Evaluation kitwhich we have used in the past is fairlyeasy to get hold of, and so we based thedesign around this unit. This meantconverting the pulses from the sensorinto a voltage. This however has anotherbenefit in that a greater resolution canbe obtained more quickly. To have aresolution of 10 RPM with a two bladedpropeller a sample time of three secondswould be necessary.

The use of the BPW34 photodiodein the photovoltaic mode, ie actuallygenerating a voltage, simplifies thebiasing otherwise needed.

SPECIFICATIONS

RPM rangeLowHigh

Resolution

Display

Detection method

Power

Battery life 9V

0 - 20 00010000 - 30 000

10 RPM

12mm LCD

reflected light

9V dc @ 4mA

about 150 hours


Light Activated Tacho

CONSTRUCTIONAll the electronic components aremounted on a single pc card with theexception of the photodiode. To saveon real estate the main voltmeter IC ismounted under the display.

Initially, assemble all thecomponents apart from the ICs and thedisplay, taking care not to bridgebetween the tracks with solder. Alsonote that some of the capacitors have tobe laid on their side to give a low height.

The ICs can now be added beingcareful to polarize them correctly. Dueto the display being mounted over themain IC it is not possible to use a socket.A socket can be used for the display ifdesired however it will have to bemodified by cutting it into two strips.

As there are no polarity marks on thedisplay it is necessary to hold it at thelight and look for the outline of thedigits. A link for the decimal pointshould be added as shown in thediagram.

We mounted our unit in a metal boxwe made with the photodiode mountedabout 25mm from the end of a 75mmlong tube in front of the box. Thisnarrows the field of view of the diodeas well as giving a little more clearance

ETI CANADA-JULY 1979

between high speed propellors and thefingers!

CALIERATIONSwitch on the unit and cover thephotodiode to prevent any lightreaching it. Now adjust RV1 until thedisplay reads zero.

Uncover the diode and point it ata fluorescent light. It will row give areading and RV3 should be adjustedto indicate 3600 RPM

Again cover the diode, then pressthe hip range button and adjust RV2to give a reading of -10000 RPM.Under fluorescent light it snould read-640ORPM.

OPERATION

This unit relies on a changing light levelfor its operation. For use with a modelaircraft, holding the unit near thepropeller enables detection of thechanges in the reflected light level. Tomeasure the speed of other rotatingequipment it may be necessary topainta series of white lines to give the sensorsomething to 'see'.

However the unit cannot be used

under fluorescent lights as it will see the120 cycle flicker (see calibration

section) . In cases where this has to bedone, and places where the ambientlight is low, a small incandescent lampcan be used to shine on the spot lookedat by the sensor.

The unit, as described, is scaled toread up to 20000 RPM with a 10 RPMresolution, assuming two input pulsesper revolution. If a different number ofinput pulses is to be used, e.g. a three orfour bladed propeller, the value ofR1 can be changed. (R1 360k /number of pulses). The use of morethan four pulses per revolution is notrecommended on this range. If 2000RPM is more than is needed for yourapplication the value of R1 can beincreased by a factor of 10, preferablywith more .than ten pulses perrevolution.

Unlike a frequency meter,overranging this unit will cause thedisplay to blank and greater resolutioncannot be obtained simply by using alower range. However an offset of afixed number of RPM can be used asdescribed in the 'How It Works' section.Using the values given, when the highrange button is pressed, 10000 RPMmust be added to the reading.

25

ETI Project

D1

PB1

9V

BATTERY

-rI clo'i_r

C7U...R12mwasC50+

R 10.4.

C4

R V2

Q1

4(APti 11

cicl +R20R21.

14

RV1

Fig. 1 The component overlay and wiring diagram of the tacho.Note that the polarity of the sensor diode, 01, is not important.

HOW IT WORKS

When using this unit to measure RPM, bethe application a model aircraft motor orsome other rotating object, the propelleror the white line ( see operation section )gives rise to a changing light level. DIwhich is a photo diode used in thephotovoltaic mode, sees this light level andgives out a voltage proportional to thelight. As this is only a small signal it has tobe amplified before it can be used. This isdone by IC3a. The transistor Q1 isincluded to provide some gain controlallowing the unit to be used in differinglight conditions without the need for anyadjustment. Ific output of the amplifier isrectified by D3 to provide a negativevoltage on the gate of Ql. When theoutput of the amplifier is small the gate tosource voltage will be neat zero and theFET will appear as a low value resistorgiving high gain to the amplifier. If thelight change is such that the output of theamplifier is large, the rectified voltage onthe gate of Q1 will cause the resistance ofthe FET to increase decreasing theamplifier gain. In this way the output ofthe amplifier is held relatively constantirrespective of the light level. Diode D2is necessary to prevent the amplifier fromsaturating on the positive swing.

The output is then squared up by IC3b

.47R8.01

QbR29+ itQ28n-1

geoR26,0- r

J L C17LL

IC4 1L \ "L

w

t-

4 I"

J

a

PCB pattern: page 73.

where the positive feedback provided byR12 ensures that the output switchesquickly. The output from this IC thentriggers the monostable formed by Q2.What we have now is a pulse about 50µslong every time the propeller blade passesthe light sensor.

Before continuing, you may havenoticed that besides the +9V and OV wealso have a line marked Vref. This isderived from IC4 which is a voltmeterchip and is a stable voltage of about2.8 volts below the +9V line.

The output of the monostable (Q2)turns on ICla for 50us, discharging C2which is then allowed to recharge to V ref.This voltage is compared (by IC2) to thevoltage set by R2 and R3. The output ofIC2 is a negative pulse of about 900µs.As it is on a stable voltage supply,variations in battery voltage will have verylittle effect on the output pulse width.Capacitor C3 is used to force the positiveinput of IC2 above the negative one forthe 50us pulse ensuring that this time isnot included in the output pulse. IC1b isused to invert this pulse and its output,and the output of IC2, control IC2c/IC2d.The output of IC2c/IC2d is a positivepulse switching between V ref. and the+9V line.

R28RV3

R25+1

C15

PCBs for this project: check with B&RElectronics, P.O. Box 6326F, HamiltonOnt. L9C 6L9. and Spectrum Electronics38 Audubon St. S., Hamiton Ont L8J1J7. The ICL7106EV is available fromNorthern Bear Electronics, P. 0. Box7260, Saskatoon, Sask., S7K 4J2.

This is then filtered by two 2 poleactive low pass filters, 1C3c and IC3d. Asthese have a cutoff frequency of around10 Hz the output for most applicationswill be the de voltage component only.This is measured by IC4 which is acomplete voltmeter.

As offset voltages and currents cancause the output of the filters not to beexactly zero with no input, the positiveinput of IC3d is biased up about 30mVand then by injecting a current into thenegative input (by R19 and RV1)correction can be made. For measuringRPMs above 20000 and below 30000 acurrent is injected into the negative inputvia R18 and this subtracts 10000 RPMfrom the reading,



PARTS LIST -

RESISTORS all

R1 180kR2 150kR3 100kR4 1MR5 47kR6 4M7R7,8 180kR9 12kR10 10kR11 100kR12 330kR13 100kR14 10kR15 33kR16 15kR17 4k7R18 120kR19 1MR20 150kR21 1k

R22 1MR23 10kR24 2k2R25 220kR26 4M7

R27 100kR28 100kR29 4M7

POTENTIOMETERSRV1,2 . . . . 50k VTP trim

RV3 1k 10 turn trimCAPACITORS

1 J../ 35V tantalumC2 4n7 polystyreneC3 1n5 polyesterC4 100nC5 1µ 35V tantalumC6 100p ceramicC7,8 1µ 35V tantalumC9 100n polyesterC10 820p ceramicC11 3)43 16V tantalumC12 1µ 35V tantalumC13 10n polyesterC14 100n

C15 220n " C16 100n C17 100p ceramic

C18 10n polyesterSEMICONDUCTORS

IC1 4016 (CMOS)IC2 301AIC3 324

IC4 ICL7106

Q1 2N5485Q2,3 2N3904

D1 BPW34 or BPx40D2,3 1N914

MISCELLANEOUSPC board ETI 555toggle switchpushbutton switch

3% digit LCDcase to suitbattery clip9V battery

Note; These components are suppliedwith the Intersil ICL7106EV evaluationkit.

O

zCS1

o?

0Fig. 2 The circuit diagram of the tacho.

Ti X

VQ

UY

..8u-

--1F--

11_41+I I

0

ZcN

om


The lonospereand PropagationRadio communications beyond the horizon in the high frequency (HF)spectrum between 3 MHz and 30 MHz are carried on as the result of thebending of the radio waves in the ionosphere, that region of ouratmosphere extending from about 60 km to about 1000 km above theearth.

The ionosphere can bend radio wavesso that they return to earth fromhundreds of kilometres to manythousands of kilometres distant.

Without the existence of the iono-sphere, long distance radio communicat-ions, shortwave broadcasting, amateurradio 'DX' etc would not be possible -and one G. Marconi would probablyhave died an unknown pauper!

The ionosphere enables shortwaveradio stations such as Radio Australia,Radio Peking, The Voice of America etcto broadcast programme:: across theworld. It enables radiotelephonecommunications to ships at sea andcontact with international aircraft.

THE SOLAR PRIME MOVERSThe sun, which dominates almost everyphase of our lives, influences all HFradio communication beyond thehorizon. The sun generates the ionos-phere; solar activity has a considerableinfluence on this area of our atmosphereand thus affects propagation of HFradio waves.

Ionisation of the upper atmosphere isbrought about largely by ultravioletradiation from the sun, along withsolar X-ray radiation. This solarradiation strips electrons from theatoms of the rarified atmospheric gasesexisting in our upper atmosphere.

The result is not a single, thick regionor 'band' of ionisation, as you maysuppose. The ionosphere separates intoseveral readily defined regions havingvarying densities, located in layers atdifferent heights.

Each layer has a relatively denseregion, called the peak of the layer, theionisation tapering off above and belowthis region. The peak is not necessarilylocated in the centre of the layer, nor

28

GROUND WAVES

Figure 1. The ionosphere bends radio waves such that they travel great distances beyond thehorizon.

F1

192Km

E

104Km

EARTH

Figure 2. The ionosphere divides into readilydefined regions which have been designated asillustrated here. The amount of ionisation ineach layer varies diurnally (i.e.: throughoutthe day), seasonally (throughout the year)and through the 11 -year sunspot cycle.Disturbances on the sun have a variety ofeffects on the ionosphere and thus on radiocommunications.

does the ionisation always disappearcompletely between layers.SPOTTING GOODPROPAGATIONThe sun's UV radiation output variesover an approximately 11 -year cycle,greatly influencing the behaviour of theionosphere. For many years this cyclicbehaviour of the sun has been monitoredby means of sunspots - dark areas

which appear on the face of the sun,and over the last two decades, bymeasurement of the solar flux (RFnoise radiation) at 2800 MHz (10.7 cmwavelength).

Sunspots are enormous areas on thesun's surface which are cooler, and thusdo not appear as bright as the surround-ing area. Hence, they look like 'spots'on the face of the sun. Their size canrange from several hundred kilometresacross to greater than 100,000 km. Bycomparison, the earth's diameter is only13,000 km.

The spots usually appear in clusters,the largest extending nearly half a

million kilometres across the face ofthe sun on occasions.

Sunspots can form and remainvisible from several days to severalmonths, often growing in size the longerthey last.

The sun rotates about its axis with aperiod of about 27 days. If a sunspotpersists long enough, it can be seen tomove across the face of the sun, takingabout 13Y2 days to go from one side tothe other (limb to limb, as they say).Having reached one side and dis-appeared, it may reappear on the otherside about 131/2 days later.

Man's interest in the sun and solarphenomena is clearly older thanrecorded history. Ancient Sumerian andChinese cultures observed and recordedsunspots. Galileo turned his telescope,


Figure 3. The sun as viewed in the visiblelight region showing several small spots, arelatively large spot and sunspot groups.(Photo courtesy of the IonosphericPrediction Service.)

the first ever made, onto the predomin-ant celestial body and observed spots!- he was labelled a heretic for tellingwhat he saw.

WARNING: Do not attempt to lookdirectly at the sun, especially through atelescope - this can result in blindness.The alternative technique of projectingthe sun's image onto a card is describedin many books on astronomy. Galileomay not have been a heretic, but if heever looked through his telescope atthe sun, he was probably a silly old twit.

Records of systematic sunspot obser-vations date back some 300 years.However, reasonably reliable data is

only available from about 1850.The sun is monitored continously

from a number of observatories aroundthe world. Sunspot observations arestatistically smoothed to provide a

continuous record - this is termed theZurich Sunspot Number, which is a

statistical 'fudge factor' on which ionos-pheric propagation predictions are based.More on this later.

Sunspot Number does not mean'number of sunspots'. It is a statisticalterm which allows comparison with pastfigures and provides an index of sunspotactivity.

The sunspot number has a cyclicalvariation with a mean period of 11 years.Periods between sunspot peaks havebeen as short as 9 years and as long as13 years. The sunspot number betweenthe peaks and minimums of the cyclesalso varies greatly. The sunspot cycleshave been 'numbered', for the conven-ience of reference, back for 200 years.Cycle 18 peaked in 1947, cycle 19 -the biggest on record - peaked in 1957with a sunspot number in excess of 200.Cycle 20 peaked in 1969 reaching asunspot number of 120, which is aboutaverage intensity.

If you thought the DX wasn't any-


thing spectacular in 1969.70, youshould have been around in 1907 whenthe sunspot number barely reached 60during the peak!

Sunspot cycle minima don'talways reach zero levels. someminima however have shown littleor no activity for many months.

The sunspot cycle, while having an11 -year mean period as observedbetween peaks, has been identified inrecent years as actually being a roughly22 -year period based on the magneticfield variations of the sun. Alternatesunspot cycles show a pole reversal inthe solar magnetic field.

SOLAR DISTURBANCESOn occasions, the surface of the sun isdisturbed by sudden 'storms'. Thesedisturbances are not normally visiblebut are readily detected when the sunis viewed at a particular red light wave-length, known as H -alpha, emitted byhydrogen.

These very intense, localised out-bursts increase very rapidly to a peak,taking a minute or less, and then theintensity of the H -alpha emission dec-reases to its normal value in about halfan hour or so.

This phenomenon is called a solarflare, usually occuring near, or assoc-iated with, a sunspot.

Solar flares generate enormousamounts of energy, and increasedsolar X-ray radiation from these regionscause disturbance to the ionosphere andto communications. Electrons andprotons are also emitted from solarflares, and these travel through solarwind towards the earth. The particlesare emitted in a stream and are muchmore numerous and move at greatervelocities than those particles contained

150iv

E 100

5 50

01700

Figure 4. The sun as viewed in the red wave-length region emitted by hydrogen -H -alphaemission. Two large active regions can be seenalong with associated 'filaments'. (Photocourtesy of the lonosphericPrediction Service).

in the normal solar 'wind'.Upon reaching the region near the

earth these particles have a considerableinfluence on the earth's ionosphere andmagnetic field, producing sudden anddramatic changes as well as precipitat-ing other events - such as aurorae -which will be described in more detaillater.

Apart from flares, disturbances notassociated with sunspots also causedisturbances to the ionosphere and theearth's magnetic field. Hot Spots -which are of longer duration than flares,are emitting regions on the sun's surfacethat expel streams of particles whichaffect the ionosphere. These, and otherareas on the sun's surface which emitpersistant streams of particles, havelonger durations than flares but theeffects of the particles emitted is lesssevere.

200 L

150

5

6 50

0

1830 1850 1870Figure 5. The 11 -year solar cycle is clearly evident from1700 to 1960.

1720 1740 1760

100

1890

1780

1910

1800

1930

1820

1950this plot of the Sunspot Number from

29

FORMATION OFTHE IONASHPEREAs mentioned before, the ionosphere isproduced principally by ultravioletradiation from the sun. The amountof ionisation produced is almost whollydependent on the strength of the UVradiation and its wavelength. Differentwavelengths of the radiation ionisedifferent gases.

The process of ionisation absorbsenergy from the UV wave, and as theradiation proceeds down through theatmosphere, it is almost completelyabsorbed in this way.

This process of creation of ions andfree electrons in the ionosphere is offsetby recombination which is continuallytaking place between the two to formneutral atoms once again.

In the lower atmosphere, the molec-ular density is so great that recombin-ation occurs almost immediately afterionisation the rate of recombinationis very rapid. However, in the upperatmosphere, where the number ofmolecules is very much smaller, thechances of a free electron meeting upwith an ion is very much less. Hence,recombination occurs at a much slowerrate.

These two opposing mechanismsresult in regions in the upper atmospherewhere a large amount of ionisation ispresent, the amount being determinedby the balancing forces between the rateof ion production and the recombinationrate.

The gases of the upper atmospherewhich the solar UV radiation meets firstare very rarified, hence little ionisationresults and little of the radiation energyis lost. As the radiation penetratesfurther, the molecular density of thegases increases and hence the ionisationincreases.

More and more energy is extractedfrom the ionising radiation as it penet-rates further and at some stage theamount of ionisation which the radiationcan produce begins to decrease. There isthus a certain height at which ionisationis maximised. The region around thisheight is known as an ionisation layer.

This is how 1, ,e ionosphere comes todel iye its name. It is the region of theupper atmosphere where appreciableionisation can take place.

The lower limit of the ionosphere isabout 50km and it extends to beyond1000km.

Sydney Chapman, a British scientist,investigated the production of ionisationin the early 1930's and showed that therate of production of ionisation wouldvary with height as shown in figure 6.The corresponding layers of electronshave been called Chapman layers.

The height of the 'peak' is determinedby the concentration at particularheights of the atmospheric gas and bythe ability of the gas to absorb the solarradiation. The less easily absorbed wave-lengths of the radiation penetrate lowerin the atmosphere before forming a layerof electrons. The height of the layerdoes not depend on the strength of theionising radiation.

gas concentration IIIrate of production,of electrons

strengthof ionisingradiation

Fig. 6. How a layer of electrons is producedwhen ionising radiation comes from above theatmosphere. The gas concentration increaseswith decreasing height while the radiationstrength decreases. Peak production ofelectrons occurs at the height where the curvescross.

The production rate of electrons atthe peak of the layer depends on thestrength of the ionising radiation andon its direction of arrival. When theradiation is vertically incident on thelayer, ionisation is maximum, less whenit arrives at an angle.

When curves representing the pro-duction rate of electrons of all possibleshapes are 'normalised' with respect tothe layer peak, they all look the same.See figure 7.

THE THREE riEGIONSThere are three main regions of the

ionosphere. They are designated by thesymbbls 'D', 'E' and 'F'. The F -layeractually divides into two layers, F1 andF2, which I will go into shortly.

The structure of the ionospherevaries widely over the earth's surface asthe strength of the sun's radiation willobviously vary with geographicallatitude.

THE D-LEVELThis is a region of low ionisation densitywhich does not show the well-defined'peak' of maximum ionisation densityassociated with the other layers.

The D -layer only appears during day-light hours and extends rather diffuselyfrom about 50km to about 90km. Thedensity of electrons in the D region isgenerally insufficient to cause appreci-

able bending of radio waves but they dosuffer considerable attenuation in passingthrough this region.

Solar X-ray radiation with wave-lengths less than about 20 Angstromscontributes to some of the ionisationin the D -layer. This radiation can ioniseall the gases present at these heights inthe atmosphere, but this alone does notaccount for the level of free electronsfound in this region.

Nitric oxide (NO) is formed atheights between 60 and 90km by aphotochemical process that diffusesatomic nitrogen down from the S-layer above 100km. This nitric oxide isionised by UV radiation from the sunhaving a wavelength of 1216 Angstroms- the Lyman -Alpha wavelength.

Hydrogen in the sun radiates verystrongly at this wavelength which coin-cides almost exactly with a 'spectralwindow' in the atmosphere which allowsthis radiation to penetrate to very lowlevels in the atmosphere with littleattenuation.

300

275

250

225

200

.t 175

_c4-150

En125_c

0 500a) per cm3 per escond

Rate of production of electrons

0

(b) normalisedFig. 7 (a) Theoretical 'Chapman' layers show-ing how electron production is affected bythe angle of the sun's rays - best when sun isoverhead (0° zenith angle).

(b) If all curves are 'normalised' about peakheight, regardless of the sun's zenith angle,they all have the same shape.

1000

0.5 1


The lonospere and PropagationBecause it penetrates down to where

the nitric oxide is produced there is anabundant supply of electrons whichcontribute to the general ionisation ofthe D -layer at a height of around 75km.Solar X-ray and Lyman -Alpha radiationcontribute in roughly equal proportionsto the ionisation of the D region. How-ever, the strength of the X-rays varies bya large factor both daily and throughthe solar cycle as well as with solardisturbances. There is no appreciablechange in the strength of the Lyman -Alpha radiation.

Increased X-ray radiation associatedwith solar flares can increase the ion-isation of the D layer thus causingincreased absorption of radio wavestravelling through the D region. Thesesolar disturbances can be the cause of acomplete 'radio blackout' at times.

Ionisation in the very lowest part ofthe D region is caused by cosmic radi-ation which consists of high velocitycharged particles coming from distantparts of space. They impinge on theearth more or less constantly and canpenetrate right to ground level withlittle loss in energy. The rate at whichthey produce free electrons and ions isrelated to the density or concentrationof air molecules available to be ionised.

As cosmic rays are deviated by theearth's magnetic field ionisation of thelower D region is greater near the mag-netic poles than it is near the equator.

Since the D -layer absorbs radio wavesit affects the propagation of radio signals.During the day signals below about5MHz are almost completely absorbed.Only signals radiated at a very high angle,and above a critical frequency where allsignals are absorbed, manage to passthrough the layer, being subsequentlyreflected by the E -layer.

Communication during daylight hourson the lowest frequencies of the HFspectrum from 3MHz to about 5MHz orso is thus limited to short distances,not much beyond ground -wave coverage.

Low angle radiation on these fre-quencies during the day travels a longway through the D -region and is thusabsorbed.

The D-llayer of course affects higherfrequencies but its attenuation affectlessens as the frequency is increased.

THE E7 -LEVELThis occurs during daylight hours, themaximum density or peak of the layerlying between about 100 and 150km.It remains weakly ionised at night.

During daylight hours it stays atpractically a constant height. The heighthardly varies from day to day. The elect-ron density of the E -layer is lower inwinter than in summer as the obliqueangle of the solar radiation reduces theionising effect.

E -layer ionisation is produced jointlyby X-rays having wavelengths less thanabout 1C0 Angstroms - this ionisingoxygen and nitrogen in the upperatmosphere at heights close to 100km -as well as UV radiation with wavelengthsnear 100 Angstroms which ioniseoxygen.

The atmosphere in the E -region is

still dense enough for recombination totake place fairly rapidly. As a con-sequence, the E-Iayer can only maintainits signal' reflecting ability when it is

continuously in sunlight.Ionisation is generally the best around

noon, disappearing rapidly some timeafter local sunset. (The sun sets on theionosphere at a height of 100km abouthalf an hour after local sunset.)

From a simple consideration of thegeometry of the situation, communic-ations via the E -layer has a maximumdistance of about 2000km. See figure 8.

THE F -LEVELThe F -layer is that region of the ionos-phere above about 150km extending upto 800km and beyond.

During daylight hours, two distinctlayers appear in the F -region of theionosphere - the lower is known as theF1 layer, the upper as the F2 layer.

Fig. 8. Geometry of E -layer propagation. As the layer height is about 100 km, low angle radiationfrom a transmitter will reach distances of about 2000 km maximum.

The F1 layer generally occurs arounda height of 200km and does not varygreatly in height. Its ionisation densityis lower in winter than in summer.

As one would expect, the F2 layer,being the uppermost has the greatestionisation and shows considerablevariations in density and height.

The height of the base of the F2 -layer during daylight hours is verydependant on solar heating of the upperatmosphere. It varies between about150km and 300km during wintermonths.

There is only one layer during thenight in the F -region which is likewisedependant on atmospheric temperature.The height and density of the night-time F -layer is also very variable owingto a number of factors.

Figure 9 illustrates typical variationsof the F -layer throughout the day

The principal ionising agent of theF -layer is the extreme ultra -violet region(EUV). Solar UV with wavelengthbetween about 200 and 800 Angstromsdoes most of the work in this respect.Radiation at these wavelengths ionisesmolecular nitrogen and atomic oxygenat heights between about 150 and180km.

The resulting electron distributionwith height does not always show apeak at this level- when there is a

peak it is usually that of the Fl layer.

The shape of the F2 layer electrondistribution, and thus the height ofthe peak, is largely determined by thevariation with height of the loss processand by diffusion of the electrons toother regions. Ions and electrons diffuseabove the peak of the layer, the pro-duction and loss of electrons (byrecombination etc) below the peakdetermine both the position of thepeak and the shape of the layer. Thepeak then occurs at a height where theeffects of diffusion and loss of elect-rons reaches an equilibrium.

The F -layer will provide communic-ations out to a range of 4000km on asingle 'hop', multi -hop propogation beingused for distances greater than this.

The F1 layer will provide com-munications up to about 9 or 10 MHzduring the day. The F2 layer willsupport propagation beyond 30 MHzunder favourable conditions, eve, higherin frequency and for longer durations atlower frequencies, during a sunspotmaximum.

The maximum usable frequency ofthe F -layer varies seasonally. beinggreater during summer than duringw.nter.


400 Km

virtualheight

200 K

F

F1

0 6 12

LOCAL TIME

WINTER

18 24

400 Km...,

virtualheight

200 Km F 1

F2

F

6 12 18 24

LOCAL TIME

SUMMER

Fig. 9. Typical diurnal (daily) variations of the F -layer and E -layer heights for winter (left) andsummer (right), as measured by an ionosonde - an instrument which measures the parameters ofthe various ionospheric layers.

F2

AA)/

(B)1 4 !I

I i<

IONOSONDE TANGENT

4-0F2 MAX

4000 KM

Fig. /a The transmitter (TX) radiating BF at several different angles illustrates how signals arepropagated by the various layers. A wave radiated at a high angle will be deviated by one or bothof the layers, but unless the layer is dense enough, will pass through (A). A ray at a lower angle(B) will skip a relatively short distance and may do so several times (R2 - R4 etc.). A low angleray from TX will skip a maximum of 4000 km from the F2 layer (TX to R3) and subsequentlyfurther. The ionosonde measures the heights and critical penetration frequencies of the layersvertically.

400 Km

300 Km

200 Km

100 Km

F1

WINTER DAY

WINTER & SUMMERNIGHT

SUMMER

Fig. 11. Illustrating the diurnal and seasonal variations in the various layers.

Figs. 6 & 7 after J.A. Ratcliffe, 'SUN, EARTH AND RADIO', World University Library, 1970.In fact, if you want a good book on the subject, complete with charming historical anecdotes -this is it.

SUMMARY SO FARThe daytime ionosphere consists of anabsorbing region - the ID -region -with three reflecting ionised layersabove that - the E, F1 and F2 layers.

The night-time ionosphere consistsalmost entirely of the F -layer.

It should be noted that the alloc-ation of the letters of these layerswas made by Sir Edward Appleton.It was he who did most of the earlyinvestigative work on the ionosphere.The F -layer, which he discovered, isalso known as the "Appleton Layer".The E -layer was originally named the"Kennelly -Heaviside Layer" (or justthe Heaviside Layer) after the twogentlemen who discovered its existence.

LONG DISTANCE propagation onthe HF bands is not all by means ofmulti -hop reflections between theionosphere and the earth. Considerabledistance can be covered, or paths notsupposed to be 'open' can be worked -often well beyond the MUF - by meansof a variety of "anomalous propagation"modes.

The ionosphere is not an homo-genous medium. The cream is not mixedin with the milk, so to speak. It is acurious mixture of 'thick' patches and'thin' patches, bulges and tilts -all the time on the move under theinfluence of a variety of forces. Someof which have already been explained.

"CHORDAL HOP"The base of the ionosphere is not 'flat',nor parallel to the earth's surface inmany places. This characteristic givesrise to 'tilts' in the base of theionosphere which can be exploited toprovide multiple reflections from theionosphere without intermediate groundreflections.

This is now commonly referred to as"chordal hop" propagation. Theconcept is illustrated in Figure 12.

When tilts occur at suitable pointsalong a path, particularly at theionospheric reflection point nearesteach terminal of a path (the 'controlpoint'), then chordal hop propagationoften results. If a signal arrives at a tiltat a suitably low angle, then theionosphere will support propagationwell above the 'predicted' MUF and willalso provide extremely strong signals onlower frequencies as the signal willspend less time travelling through the13 -layer together with the decreased lossthrough successive ground reflections.

Chordal hop propagation has beenexploited by amateurs working fromBritain to Australia on several of thelower HF bands. Tilts occur in the baseof the ionosphere at the 'sunset' zone


The lonospere and Propagationand at regions either side of thegeomagnetic equator. Using the tiltsouth of the geomagnetic equator in theIndian ocean area, and the sunset tiltover the Mediterranean, British andWest Australian amateurs have been ableto make contact on the 3.5 and 7 MHzbands at times when they wouldnormally be 'closed'.

Low angle radiation from theantenna is necessary to exploit thesemodes but due to the ionosphere"focussing" the signal rays, and the lowangle of incidence on the ionosphere,very little power is necessary to producesurprising signal strengths.

"PEDERSON RAYS"Anomalies in the electron distributionwell within the F -layer can entrapsignals so that a sort of totalinternal reflection phenomena occurs.A signal trapped in such a manner cantravel surprising distances, again withoutintermediate ground reflections, andre-emerge from the ionosphere viaanother anomaly or tilt.

Signals travelling through theionosphere in this manner are referredto as Pederson Rays after the man whofirst described them. The phenomenonis illustrated in Figure 13.

A Pederson Ray generally travelsthrough the ionosphere at considerableheights and experiences more "loss"than chordal hop signals. However, it isoften experienced where high radiationangles occur from an antenna so thatthe signals enter the ionosphericanomalies at a favourable angle.

TRANSEQUATOR IALPROPAGATIONThis mode of propagation wasdiscovered by radio amateurs in 1947.Confirmed contacts on the 50 MHzband between amateurs in the USA andSouth America exploited certaincharacteristics of the equatorialionosphere unknown at that time andwhich have taken some 30 years ofresearch to explain - and it's notfinished yet!

There are two types of TEP knownas "afternoon -type", or class 1, and"evening -type" or class 2.

Afternoon -type TEP is a true chordalhop propagation mode and occursgenerally between 1200 hours and 1900hours local mean time. Statioris situatedin the zone between about 20° and 40°geomagnetic latitude are able to contactstations in a similar zone on theopposite side of the geomagneticequator. Figure 14 shows the

Australasian sector of the world withthe class 1 zones cross -hatched thus: ////.

Evening type TEP is generallyexperienced between 2000 hours and2300 hours local mean time and stationslocated in the area between 10° and30° geomagnetic latitude (cross -hatched\\\\ in Fig. 14) can contact stationsin the similar zone on the opposite sideof the geomagnetic equator.

Transequatorial propagation is pre-dominantly an equinoctial occurrence,peaking in the months March -April andSeptember -October but it can occurover many more months around theequinoxes (21 March and 21

September), particularly during highsunspot activity.

The propagation modes for bothclasses of TEP are illustrated in Figure15. The afternoon -type mode is

generally called a "supermode". Thesignal is reflected from two dense'bulges' in the ionosphere located eitherside of the geomagnetic equator. Thedensity of these bulges, and the tiltsassociated with them, cause 'rayfocussing' which gives rise to thesurprising signal strengths observed onafternoon -type TEP signals. Fading onthese signals is small; propagationdistortion experienced on 'normal'ionospheric modes is absent giving riseto good quality signals as well.

Signals up to 65-70 MHz may bepropagated by class 1 TEP, whichrepresents a considerable extension ofthe conventional MUF for these paths.Occurrences will increase in comingyears as the sunspot activity increases.

The best paths for class 1 TEP arethose which cross the geomagneticequator at angles close to 90°. Evenso, paths which have considerableobliquity - such as USA to Australia- are occasionally bridged during goodconditions.

Evening -type TEP is a "field -guided"mode. The equatorial bulges (X and Yin Fig. 15) that exist during the after-noon in the equatorial region of the

IONOSPHERIC GROUNDREFLECTION

Fig.12.

REFLECTION

(a) lb)

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c' Wt3,Da *;"

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Fig.14. Australasian sector of the worldshowigg terminal zones for class I TEP (20-to 40 nomagnelic latitude) and class llTEP (10"to 30- geomagnetic latitude).

ionosphere break up after sunset andthe ionosphere over the geomagneticequator develops dense 'slags' ofionisation which align themselves withthe earth's magnetic field. If a signalis sent towards this area of theionosphere so that it arrives more or lessat a tangent to the magnetic field then itmay become 'trapped' between the'slabs' of dense ionisation andconducted across the equator bysuccessive reflection from a series ofthese irregularities.

Again, signals will be quite strong onevening -type TEP but considerable'flutter' fading is generally experienced- generally at a rate between 5 and15 Hz.

Evening -type TEP will supportsignals of much higher frequencies thanfor afternoon type. Until recently, it

CHORDAL -HOPPROPAGATION

SURFACE WAVE

TILTTI

Ic)

PEDERSON RAYPROPAGATION

Fig.13.


The lonospere and PropagationF -layer

Fig. 16- 'M -reflection' - a complex propagation mode involving reflections from the F -layer andE -layer without intermediate ground reflection.

F -layer

Fig.17. A complex chordal hop mode involving reflections from the F -layer and E -layerwithout intermediate ground reflection.

Fig.18. A complex propagation mode involving one F -layer hop and one E -layer hop. Some-times referred to as "N -reflection".

The propagation modes of class I and class II TEP.

Mognetic field-olignedirregolorities

Lina of equolelectron density.

BULGE

CREST -

c

Goontagnticlatitude

Sterner*, itEquator

Geogrophic&quote,

CREST

2 es

eomeerietic...re,so

tot,tud

Fig.15. The Propagation modes of class I and class ll TEP.

was thought that the limit was in thevicinity of 100 MHz, but recent contactsbetween Australian and Japaneseamateurs, as well as Puerto Rican andArgentinian amateurs, on the 144 MHzband clearly indicate that there is moreto be learned about this mode ofpropagation.

Evening -type TEP is much moretolerant of path obliquity than

afternoon -type. However, the pathsare generally shorter.

The zones for each class of TEPshown in Fig. 14 are calculated from thegeometry of the propagation mechanismand don't necessarily indicate the limits.Amateurs from Sydney right down toHobart have worked into Japan on thesix metre band on many occasions, viaclass 1 TEP.

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001


Video CassetteRecordersNo one yet knows what effect the ability to record TV programs willhave. Suffice it to say it is extremely entertaining to be able to seewhat you want, when you want, Steve Rimmer surveys the currenteasy to use machines.

"HEY MEESTER" Croaks the shadowyfigure on the outskirts of the yellow pallof the street lamp. You turn to face thesource of the accostation with grim,hard bitten reserve. "Mebbee youwanna buy some peechures?" Thegrey, hunched figure approaches you,two grimy palms crushing the lapels of arain -streaked Moroccan leather greatcoat. You flash a non-commital smile.He continues . . . "These peechures arevery eenteresting, no . . . I was geeventhem by a good friend of mine... een theEast." The man's perspiring, beardedcountenance leers out from beneaththe mildewed Fedora atop his gleamingskull, his rotted grin, flecked with dulledgold, scanning your own face like theeye of a sniper. "There are several fromweech to choose." With a cobra -likeflick of his sinewy wrists he tosses backthe flaps of his coat, revealing apatchwork of inner pcokets, each onesurrounding a small black box. "And allare available in Beta and VHS format.."

Life is but a commercial.Actually, far from being an

underground industry, video cassettesof unedited "adult entertainment" (dirtymovies, if you don't wish to assume thefaçade) are currently available bothretail and by mail order from severaldozen sources, many dealing innothing other than pre-recorded tapes.Fare ranging from the most esotericforeign flicks to full length, non "editedfor television" Hollyw000d features,some available on tape even before theyappear on the tube, can be purchasedfor viewing in the convenience andcomfort of one's own home.

FAMILY FUNOr, perhaps you're tired of sit-comms

and movies, and would like to use theidiot box to renovate your mind.Whereas several years ago the only wayto do this might have meant pulling theplug, it is now possible to buy tapes

covering everything from Orientalcooking to thetechniquesof fencing toct. . electronics, for that matter. There'seven one out providing instructions forservicing a VCR.

That one should probably be playedbefore you need it.

Of course, a VCR can still retain itsprimary function; that of recordingtelevision programmes. The presentgeneration of home video machines iscapable of watching one show whileyou're tuned into another, and playingback the programme you might havemissed otherwise later on. In fact, thenew machines now incorporate built-intimers, and are thereby capable ofswitching themselves on and off totapeshows while you're asleep or away.

You can do the late late lateshow overlunch, and never miss Godzilla tearingapart Tokyo again.

At the other end of the spectrum, thereally dedicated home videoenthusiast

can now purchase either a black andwhine or color video camera to attach tohis recorder, and film his ownextravaganzas. You can now rememberthe best moments of the f ive weeks yourmother-in-law came to visit for as longas you wish (video tape is erasable, ofcourse), re -live your wedding long afteryour divorce and even spy on theneighbours electronically.

Yes, television makes all men equal. Ifyou can't be a big wheel, at least you canbe a big brother. Hide the camera in apotted plant!

HISTORYUntil recently, video machines were

really quite simple, especially from theoperator's point of view. A signal gotstuck in one end, the tape rolled, whenthe recording was finished it wasrewound, it rolled again, and the signalre-emerged. Getting heavily into"deluxe" features usually meant

How to insert a video cassette. After years of speculation, VCR's are finally start-ing to appear in the home.


adding a "pause" control. Now,however, the actual recording systemsare only half the fun. Some of the latestmodels of home VCRs have enoughbuttons, knobs, switches, levers, lightsand infernal wizz-bangs to launch amissile.

While it has been suggested thatseveral of the early model home VCRswere somewhat rushed throughproduction in order to beat thecompetition into the new market, all ofthose early machines have beensuperceded by later models, and, as faras quality of construction and reliabilitygoes, there does not appear to be muchdistinction between the various brandsavailable. The choice, then, regardingwhich machine to squander the familyfortune on must be made on a basis ofwhich features the individual userwants. Here, in a rather bloatednutshell, is what is available.WHAT'S A VCR

Starting from the middle, (a logicalbeginning) let us considerfrom whencethe video signal which is to be recordedwill come. Many home videoenthusiasts intend, at a later date, topurchase TV cameras to attach to theirVCRs, dreaming of creating little Hitch-cock epics in the living room. However,at the moment, cost more than therecorders themselves. As such, plan onmost of your recording being done frombroadcast television transmissions, atleast for a while.

To get video out of the airwaves, oneneeds a tuner: essentially, a completeTV set without picture tube or speakercircuits. Most home VCRs have built intuners which accept an input fromeither your antenna orcable TV line, tapoff some for themselves and send therest on to your television set. With thisarrangement, it is possible to have themachine recording one show whileyou are watching another. A great wayto end family fights.

There are a few systems which offerVCRs without built in tuners. These aremachines designed primarily forportable operation, usually with acamera. If so desired, a separate tunercan be purchased to facilitaterecording off the air.TUNER TYPES

To further confuse the tunersituation, all tuners are not createdequal. There are basically two types;the rotary, mechanical tunerwith whichwe are all familiar, also called a turrettuner, and the electronic, pushbuttontuner in which a series of switches isused to apply predetermined voltagesto a tuning diode, also called a very

expensive tuner. Each type has itsadvantages.

The electronic tuner is more reliable,and can be switched automatically bythe machine (more on this in a minute).As each channel switch can beassigned to tune in any VHF or UHFstation, one is not restricted to anyspecific stations. However, there is alimitation as to the number of stationsone can pre -programme. Twelve tofourteen buttons are usually provided.

On the other hand, rotary tuners mustbe manually operated, and will requirecleaning now and then, but can tune inas many channels as are available.

TIMERSOne of the most useful applications

of a home video machine is therecording of programmes which wouldotherwise be missed when you areaway or sacked out. For this reason,most machines are equipped with atimer to turn them on and off at pre-determined times.

There are also two types of timers.The first is simply a digital clock with arelay in the "alarm" ci rcuitto actuate therecording mechanism. This type oftimer is usually found on VCRs withturret type tuners. The second is a bitmore complex ... in fact, you may needa degree to operate it. Many of the"deluxe" machines have built in micro-processors which can be programmedwith a set of switches to turn the VCR onat a desired moment, record for anylength of time from one minute to aslong as four hours, and then switch off.At any later time, the computer can turnthings on once again, change thechannel (hence the need for electronictuners), and repeat the whole process,again, for any interval desired. Systemswith capacity for recording up to fourdifferent programmes completelyunattended are available.

Are you with me so far?AD STOPPERS

If you are recording a programme ottthe air while watching it, a favorite flickto preserve for future edification,perhaps, you will probably want toeliminate about twelve minutes of everyhour of material, these being thecommercials and station breaks. Inorder to allow you a convenient way tostop the machine when the Saturdaynight movie goes for a beer, most VCRsincorporate a "Pause" feature whichallows the user to instantly stop thetape. Tape motion can be resumedwithout hitting the record button again.The "Pause" function can usually beactuated either by a front panel switchor a control on a long cable, forarmchair operation.

Leaving the "pause" pausing for anextended period of time, such asduringa Prime Minister's speech, may causethe video heads and tape to becomeworn, so many machines have built-intimers to resume tape travel automat-ically after three to five minutes.

ACTION STOPPERSSome machines are capable of

producing stop action images,essentially displaying one frame of therecorded picture for as long as isdesired. In this case, the "pause"control for recording may become the"Freeze Frame" button on playback.

SLO-MOIf "Freeze Frame" stri kes you as being

a bit too slow, several VCRs areavailable with "Slow Motion" controls,which allow a smooth variation of theplayback speed from the regularplaying mode right down to a dead stop.This is just the thing for rabid hockeyfans.

FAST FORWARDOn the other hand, if an

undetermined portion of a cassette isdiscovered to be occupied by Mork andMindy, one would be justified inwishing to skip over it with all dispatchand locate the beginning of the nextprogramme on the tape. To this end,some machines are equipped with adouble speed playback ci rcu it to permitrapid searching for a desired selectionon a tape without having to watcheverything prior to it.

SOUNDMost VCRs incorporate an "Audio

Dub" feature, allowing one to record anew soundtrack on a tape withoutdisturbing the existing video.

JACKS, SWITCHES, ETC.Most VCRs have built in jackstoallow

video and audio to be brought into theset directly, primarily to facilitate theuse of a camera, or for dubbing a tapewith a second VCR, and out again, todisplay the picture on a monitor andplay the sound through a stereo system.Some have the jacks up front, whichmakes connections easy, and somehave them on the rear apron, which issomewhat less convenient, but a lotneater for asystem which is not going toget patched and unpatched all thatoften.

If you intend to use a camera withyour VCR, the switch selecting betweenit as a source foraud io and video signalsand the machine's internal tuner willprobably be used quite frequently.Some machines have it on the frontpanel, some hide it behind a little trap


Video Cassette Recorders

door and some tuck it away on the rearapron.

In some cases, it becomes necessaryto adjust the tracking of the video headsduring playback in order to produce aperfect picture. A knob is usuallyprovided. Since this adjustment israrely needed (generally only whenplaying tapes made on anothermachine), the knob does not really haveto be on the front control panel ... wheresomebody will probably fool aroundwith it. Some machines hide thetracking control on the rear apron or inthe same cubby hole as the sourceselector switch.

SPEEDSMost of the home VCRs now available

have two speeds for recording andplayback. The higher speed gives nearperfect reproduction of the recordedimage, while the slower one issomewhat more economical of tape, ata slight loss of picture quality. A fewmachines are available with only thelower speed.

With some recorders, it is necessaryto manually set the speed when playinga tape back. In the more sophisticatedsystems, though, circuitry has beenincorporated into the machines todetect the frequency of the recordedsyncronization pulses and adjust thespeed accordingly.

HUMIDITYMost machines have special circuitry

which detects excessive moisture in theinterior of the VCR's cabinet anddisables the tape transport mechanismuntil things get dried out. Moisturebuildup on the head drum can damageboth the heads and the tape. Themoisture detection circuitry has severaltrade names, but is usually called aDEW alarm.

Some DEW alarms do more than juststop all the wheels from rolling. In a fewmachines, they switch on internalelectrical heaters to dry things out.Other machines have provided holes toblow a hair dryer through, which isbetter than nothing. Somewhat. If youaren't planning to shower with yourVCR, extensive DEW precautions maynot be all that vital.

TAPE PATHThere are three basic types of

systems for getting the tape out of thecassette and into the workings of themachine. All employ dozens of littlemechanical munchkins to handle it.The Beta recorders use the U system, socalled because the tape describes a


path that resembles a drunk U. It is awonderfully confusing system, butsince all Beta recorders use it, you don'thave to try to understand it (and I don'thave to try to explain it). Some VHSmachines use the B system. A few usean M system, which ties up less tape inthe machi le, and thus makes loadingand unloading a bit faster. It does,however, also appear to have a largerprofusicn of springs, levers and thing-amajigsrnoving around, which makes itsomewhat more prone to Murphy's law.And Murphy, of course, was an opti-mist ... read the warranty card!

THE SYSTEMSLastly, tnere are two main formats of

tape systems currently in u3e withhome machines, these being Sony'sBeta system and Japan VictorCompany's (JVC) VHS system. Theyare not compatable, nor are they everlikely to be. The Beta systemcan run fora maximum of three hours, while VHScan go for four. The Beta system,furthermore, comes in two varieties;Beta I and Beta II. Beta II machines areequipped only with slow speed, so thattapes made on two speed machines athigh speed will not play back on them.The following are the VCRs which arewidely available in Canada at thepresent time. All prices areapproximate Canadian, except wherementioned otherwise.

The RCA VT 201.If you think this is neat,turn the page.

VHS Format

RCARCA has two VCR models in its

current "SELECTA-VISION" line, bothof which use a VHS compatable format.

The VCT 400 is the top of the line inRCA's offerings. Styled very similarly tothe professional 3/4" decks, features justabout every gadget imaginable. Theseinclude a DEW alarm which de-activates the tape transport if theinternal humidity of the machineexceeds a safe level, a fourteen Duttonelectronic VHF -UHF tuner and aprogrammable seven day timer withcapacity for up to four differentrecordings. An additional feature ofthe timer is its ability to record the sameprogramme every day, if desired, for aslong as there is still tape on the cassette.The "Pause" feature of the machine canbe actuated by either a front panelswitch, a remote control (provided) orby the trigger mechanism on anoptional camera. The tape counter isfitted with a mechanism to stop the tapefrom rewinding past any point wherethe counter has been set to zero ifdesired, thus simplifying the location ofthe beginning of a programme. The

37

machine is equipped with an audio dubfeature to replace existing soundtrackswith your own renderings of HonkyTonk Women on the kazoo. All useroperated controls areeither on the frontpanel or behind a front panel trap door,and all inputs, with the exception of themic input jack for audio dubbing, are onthe rear apron.

The current list price is $1800.The VCT 201 is physically different

from the 400, but electronically, quitesimilar. Several of the costlier featureshave been exorcised from this model,however, bringing the price downsomewhat. The tuner is a rotary,mechanical type, which, although notquite so futuristic, does provide fullVHF -UHF coverage, with anunrestricted number of channels. Thenon -programmable timer can only beset for one recording at a time, but iscapable of switching the recorder offafter any given length of time, asopposed to simply letting the tape runout. RCA cites this model as beinginherently more reliable due to itssimpler design.

This one is $1600.

JVCThe JVC Vidstar line consists of two

very different machines, both using theVHS format pioneered by JVC.

The HR -3300U is the firm's homeVCR -tuner entry. Its styling resemblesone of the more expensive stereosystems, with a large, front mounteddigital display to serve as the timerreadout as well as a straight clock. Thetimer is of the non -programmablevariety, and can be set to record up tofour hours of continuous television, butwon't do any channel hopping. Thedigital tape counter has a feature whichwill automatically stop the tape, onrewind, at any arbitrarily selected zeropoint. All important controls and theaudio dub mic input are mounted on thefront panel. The primary tape functionkeyes - play, record, stop, and so forth- are large, bat handled affairs foreasyoperation. Furthermore, their functionshave been labelled both on the front andtop of the machine, making the legendsreadable both from above and at eyelevel.

The current price is $1530.

A new model, the HR -3600 isexpected very shortly. It will beessentially similar to the HR -3300U, butwill include a variable speed feature,and a remote "pause" control. The pricewill be about the same as for the 3300.

The HR -4100 is a scaled downversion of the 3/4" portable decks which

RCA's VCT 400. Note the all electronic tuning.

have recently found considerableacceptance in professional televisionnews gathering systems. Using eitherinternal batteries or an external powersupply/battery charger (supplied withthe unit), this briefcase sized VCR cango anywhere, regardless of theexistence, or lack thereof, of suitableAC power. With its optional colourcamera attached, it can become acomplete one man portable studio (yousupply the script girls). The machineincorporates a DEW warning to shutthings down if the heads get too damp

The HR -3300U from JVC's Vidstar line.

plus an electronic indexing system tolocate where you began on the tape.

What separates this machine frommost of the other home VCRs is that itdoes not have a built in tuner and timer.These two features are purchased inanother package, called a TU-41AU.This gives the 4100 a decidedadvantage in terms of size and weight insituations where portability isdesirable.

The cost of the HR -4100 VCR is$1400., and its companion TU-41AUtuner is an additional $450.



The HR4100 is a portable deck without tuner. Battery operation extends theusefulness of this unit.

HitachiHas one current model in the home

VCR race,a VHS format model which, insome ways resembles theJVC machine. . . and, obtusely, looks a bit like aphotocopy machine.

The VT -5000A is the "latest in a line ofcontinuing developments in VCRtechnology", and features a twelvebutton electronic tuner, a twenty fourhour digital clock -timer, an audio dubfeature and a motor -tape handlingarrangement which allows the cassetteto be fast forwarded or rewoundsomewhat more rapidly than is possiblewith most other machines. There is amemory system to allow rewinding thetape back to any pre-set point, and,something rather unique, a DEWwarning which not only prevents themachine from operating when there isadanger of tape and head damage due toexcessive moisture, but actually turnson a heater to dry things out. All of theinput jacks, with the exception of theantenna connections, are on the frontpanel for easy access, along with all ofthe frequently operated controls.(There are indications that the unit alsoincludes an optional four slice pop-uptoaster and a sabre saw.)

The suggested retail price, notincluding tax and governmentskimming, is $1700.

An earlier model, the VT -4200, mayalso still be available in some areas. It isessentially the same as the VT -5000A,but without quite as many gadgets (notoaster . . . sorry). The tuner is of themechanical, rotary type, and the highspeed tape system is not employed.This model originally sold for about the


same price as tne V I -5000A now retailsfor, but as Hitachi has discontinued itsproduction, existing units may beavailable at a discount.

PanasonicPanasonic got into the home VCR

race a bit late (just slightly behind ourtime, this time) with its Omnivision lineof VHS recorders. At present, itincludes two models specifically aimedat the home market, plus several othersintended primarily for the industrialuser.

The PV -1500 is similar in some waystc the RCA VCT-400, with a completeline-up of every imaginable feature.These include a sevei dayp-ogrammable timer, a fourteenchannel pushbutton tuner, a DEWc rcuit to prevent the machine fromdoing a head destructo if the internalhumidity is too high, and a tapeindexing system to permit the machineto rewind the tape to any pre-set point

Hitachi's VT5000A, one of the more advanced machines in our survey.

The VT4200. This unit has been discontinued, but shopping around could un-earth one if you were so inclined.

39

PV 1500 from Panasonic. Another one of the 'thinking' machines.

for easy replay. One nice touch on thismodel is a convenience outlet on therear apron into which can be pluggedthe TV set's power cord, thuseliminating one more cube tap.

The suggested list price is $1850.The PV -1100-K is an economy model

of the PV -1500. (Spotting something ofa pattern in marketing strategies yet?) Itis essentially the same as its big brother,electronically, but uses a mechanicaltype tuner and a non -programmabletimer.

It costs $1600.

Beta FormatSony

The daddy of the Beta system format,presently has two models on themarket, both of which are all butidentical. The one difference betweenthe two is that the SL -8200 offers achoice of two speeds in which it canrecOrd and playback, allowing eitherone and a half or three hours ofrecording time on an L-750 cassette,while the newer SL -8600 offers only aslow speed, with the maximum threehour time. Sony claims that the signalprocessing circuitry in the SL -8600makes the slow speed reproductionequal to or better than that obtainableon fast speed with its older machines.

The SL-8200/SL-8600 is styled muchlike a studio model 3/4" deck. It incorp-orates a twenty four hour timer, and amechanical, rotary type tuner. It hasthree coloured indicator lights whichcome on when one of the primaryfunction keys, "play", "record" and"pause", is actuated. The remote

"pause" control also has a light builtinto it, a yellow LED, which flasheswhen the machine is in its "pause"mode. An. internal timer keeps youfrom pausing for longer thanthree minutes, to avoid excessive headand tape wear. The machines lack a fewof the features of some of thecompetition, including audio dubcapability, DEW warning and/or adehumidifier and, in the case of the SL -8600, a two speed control. However,both come in at a bit less than any of theconsole models VHS VCRs.

The list price for either machine is$1450.

ZenithKR 9000 W bears a striking

resemblance to the Sony machines,both in terms of physical appearanceand features. There is a twenty fourhour timer to make the machine watchprogrammes you'd rather not, and arotary, mechanicill type tuner. A handyconvenience outlet is provided on therear apron to plug your set into. Themajor difference between the Zenithand Sony systems appears to be thelight on the "pause" control ... which isred in this case. However, if you canabide by the red lamp, the tag on theZenith machine is somewhat less.

Current list price is $1400.

Zenith's contribution, the KR9000W.

From the creators of the Beta system. The SL8600 from Sony offers slow speedfor longer playing time.

40ETI CANADA-JULY 1979


ToshibaToshiba markets three VCRs, which

are a sort of Beta version of JVC'ssystem. The V-5310 looks likesomething out of Star Wars, the casebeing almost entirely gleamingbrushed silver in colour (also availablewith woodgrain side panels, if youaren't quite as spaced out). It has arotary type tuner, and a twenty fourhour timer. Like the Sony and Zenithmachines, it has several front panellights to indicate which mode thesystem is in. Unlike the previous twoBeta entries, however, it also has a fewof the more deluxe features, such asaudio dub and a DEW sensor. It goesthis last one a bit better, in fact, byproviding a little trap door in the top ofthe machine's case to blow hot air froma hair dryer through if the internalworkings need drying out.

The price, is including a tape andsalesman's Christmas bonus is $1400.

The V-5530 is similar to the JVC HR -4100, except, of course, that it uses JVCcassettes. It combines all of the featuresof the V-5310 with a choice of battery orAC operation, allowing completeportability. By attaching the optionalIK-1610 colour video camera, it canbecome the ultimate home moviecamera. Alternately, the optional TU-530 tuner can be connected, andrecording made from off the airbroadcasts in the traditional manner.The tuner incorporates a rotary typetuner, and a twenty four hour timer, justas in the V-5310.

Another portable, the V5530.

The V-5530 goes for $1650, plus $350for the TU-530 tuner. Sell the cat.

The V-5420, Toshiba's' recentlyannounced third entry into the videomarket, is probably the most deluxeBeta machine currently available, andis a button pusher's delight. It has aseven day programmable timer whichcan be set to record any threeprogrammes on any three channelsover the space of a week. It has a twelvechannel electronic tuner of a rather ..unusual design. Instead of twelvebuttons, it only needs two; one toincrease the channel numbers, and oneto decrease them. It's called "Comput-

R-tune". Remember when they used tocall you "stupid" for spelling like that?Another technological noveltyincorporated into this VCR is a littlecoloured stripe which can be made toappear at the bottom of the TV screento indicate how much tape is left on acassette (you have to get up to turn onthe stripe). The programme finder onthe V-5420 is better than most, though;it can be set to stop either the rewind orthe fast forward functions when itdetects the beginning of a newselection on the tape, as opposed towhen the counter hits zero.

And now ... the price: $1650.

Looicit all them buttons! The Toshiba V5420 features electronic switching.


Toshiba's V5310.

SearsThis department store chain, has its

own private VCR, which will beavailable in the Fall and Winter catalog.Called simply the "Betavision", it has nonumber at all (a very innovative touch).It incorporates a rotary type tuner and atwenty four hour timer. Like the Sonymachines, it has a set of indicator lightsto tell you what the machine thinks it'sdoing, but no audio dub featureor DEWalarm (just don't take it out in the rain orswim with it.

At $1300, it is the least expensive ofthe Beta systems. Put it on the chargecard.

CONCLUSIONSWell, there you have it. Your mission,

should you decide to accept it is tofigure out which VCR you finally dowant ... and then find the bread to payfor it. (An article on this aspect of theworld of video will appear shortly inETI's sister publication, 'Video Today- Bankruptcy Tomorrow'.)

Despite its rather high initial cost, itlooks like within fhe next few years thehome VCR will become as much a partof our lives as the tube itself. Hopefully,this article has assisted you in decidingspecifically which one is going tobecome a part of yours.

Next month will mark the beginningof a regular feature in ETI discussing avariety of aspects of home video. Untilthen, stay tuned.

A TypicalHome VideoSystemI'M DEFINITELY going to buy one ofthese things: Right after I pay for theretreads on the Plymouth.

The RCA VCT-400 Video CassetteRecorder is typical of the deluxe homevideo systems now turning up. The one

Betavision from Sears(what? No model number?).

which Starword Communications,distributors of the Selectavision line inCanada, loaned me for this article ispictured atop my reasonable facsimileof a colour TV on the cover. I am havinggrave doubts regarding my ability togive it back.

After exhuming the machine from itsrather extensive styrofoam coffin, andremoving several strata of collecteddebris from the top of the television, Ifinally succeeded in getting the wholearrangement hooked up ... incorrectly,of course. The array of little screwterminals is a bit deceiving at first,especially if you don't read thedirections before beginning to fool withthem. Actually, the traditional antennaconnectors on the rear apron areintended only for UHF aerials; a type 59bushing, of the sort used for cable TVlead-ins, is provided for the VHFfrequencies. If a non -cable system is tobe used with the VCR, especial adapter,provided, matches the input to 300 ohmtwinlead. When all else fails, read themanual.

Making a recording, once onediscovers where, in all the styrofoamthey have hidden the cassettes, is aboutas complicated as running an audiocassette deck. There are no levels to set,and, in fact, no meters with which to setthem. Both audio and video have ALCcircuits, and the tuner has AFC tominimize distortion caused by finetuning errors. The tape prowls by atabout half the speed of an audiorecorder, making one suspect that thelast guy who had this machine mighthave spilled coffee into the ventilatinggrill. However, upon playback,

the picture and sound are indistin-guishable from the live ones a fewminutes earlier. Simply blows the mind.

The front panel has a switch whichselects between "SP" and "LP". This iseventually determined to indicate"Standard Play" and "Long Play". Now,if the tape seems slow in the regularspeed . . . it's going so slow in theextended mode it could be in reverse.Still, on playback, the image quality isacceptable, although it does get a bitgrainy in places. Patching the "AudioOut" jack of the VCR into a high fidelityamplifier and a decent speaker, there isa noticeable drop in sound quality in the"LP" mode, however, when runningthrough the half ounce speaker in theTV, both sound the same. So far, veryimpressive. It does everything but makethe popcorn and shut the dog up.

The tuner is a bi different from whatmost of us are used to . . . no knobs.Instead, it has fourteen little silverbuttons that glow when touched,illuminating a channel number. Inbehind a secret front panel, there arefourteen little shafts by which eachchannel can be individually tuned toreceive any VHF or UHF station.Furthermore ... ah ha ... the channelscan also pick up many of the specialconverter channels which the cablecompanies are presently adding to theirrepertoirs. Thus, for instance, I canswap one of our two identical CBCstations for a remote UHF broadcasterto get Monty Python's Flying Circus.What that we could really swap theCBC ... oh, never mind.

Probably the most interesting bit ofparaphenalia on the machine has

42ETI CANADA-JULY 1979


nothing directly to do with the videotape process. The digital clock -timer,actually a micro -processor in sheep'sclothing, can keep even the most jadedamused for hours just playing with thenumbers. Its versatility leads to adegree of complexity, though ... !didn'tget it working quite right all that often inthe first week.

Now, ve get zientific, yaFigure .1 shows a video cassette,

holding four hours worth of tape for theVCT- 400, a comparable amount ofone inch tape for the one inch systemwhich haunts my basement(a large portion) takes up a ten inch reelInasmuch as my own system producespictures which are comparable to offthe air, broadcast quality programmes(God knows that with all that tape, itshould). I was curious to see how theSelectavision compared to it. Physi-cally less taps per minute around thehead drum should mean less pictureinformation stored, which, in turn,should show up in image duality.

The shots in figures 2a and 2bfrom the same transmission. One wastaken from the playback of my one inchbehemoth, and the other from the RCAVCR. Due to . . . er ... a slight mix up inthe darkroom, I am not all that surewhich is which. The biggest problem infiguring out the problem is that both areidentical. So we decided to leave outFigures 2a and 2b to save the em-barassment.

It is only really in test pattern checksthat the difference between off the airquality and the playback from the VCRcan be seen, and of course there is

slightly more resolution with the fasterspeed.

Oh ... and Figure 3 shows the lengthsone has to go to for that extra bit ofresolution. That's about a third of myone inch system. Big.

In the end though, I would not trademy large format VCRs for one of the newcassette machines. After all, they have acertain esoteric esthetic, much moreversatility ... and, besides, RCA told meI was crazy when I tried. However, if youcan afford it, the new generation ofVCRs has a lot to recommend it,especially if you don't watch a lot of testpatterns up close.

And I've still got three weeks to playwith this one until they take it back.Thanks to Gloria Collins at StarwordCommunications for the loan of themagic box, and to Bob McEwen atMcEwen Photo for the pictures.

Fig.3 And now, a blast from the past. How to impress your neighbours and get ahernia. Actually, large format video recorders are going to be around for a long,long time.

Fig. 1 The ubiquitous Philips Compact Cassette next to one o' them upstart VHSthings. It's amazing the lengths a company will go for more bandwidth.

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trif-Atkth'414 Vni 114 1.001-SuPPutka....

41(ETI CANADA-JULY 1979 43

Practical Guideto Reed SwitchesPart 1

It used to be ships in bottles, now it's switches in glass envelopes. Actually, reedswitches have been around for a long time, but do you know what to do with them?

The dry reed is an almost perfectlow -current switch.

It is fast - operating times ofless than one millisecond are typical. Itis reliable - as many as one billionoperations can be achieved. And it ischeap - quantity price is well under50 cents.The dry reed switch is not by any

means a new device for it was inventedback in 1945 by Dr. W. B. Ellwood ofthe USA's Western Electric Cor-poration.

But it was ahead of its time. Itremained practically unnoticed by theengineering world until only a fewyears ago when it was 'rediscovered'by the telephone industry.

And since then reed switches arereceiving interest and acceptance at anever increasing rate.

In its basic form, a reed switch is amagneto -mechanical relay. In otherwords it relies upon a magnetic forceto initiate a mechanical switchingaction.

THE BASIC SWITCHA typical reed switch is shown in

Fig.1. It consists of two flattenedferromagnetic reeds sealed in a glasstube. The reeds are fixed, one at eachend of the tube, so that their free endsoverlap in the centre but with a 0.01"gap between them.

During the sealing operation the airinside the tube is pumped out andreplaced by dry nitrogen so that thecontacts operate in an inert atmos-phere.When the reed switch is brought

within the influence of a magnetic

CONTACTS

ENVELOPEFILLED WITH

I INERT GAS

REEDS

GLASS ENVELOPE

ONNECTIONS

Fig. 1. The basic reed switch.

field .(either from a coil or a magnet)the reeds - being ferromagnetic -become a flux -carrying portion of themagnetic circuit. The extreme ends ofthe reeds wilt assume opposite mag-netic polarity, and if sufficient flux ispresent, the attraction forces over-come the stiffness of the reeds andthey flex towards each other andtouch.

When the magnetic field is removedthe reeds spring back to their originalpositions. There is however a dif-ference between the value of fieldrequired to close the reeds, and thereduced value that will allow them toopen again.

MAGNET POSITION MAGNET POSITIONFOR PULL -IN FOR DROP -OUT

Fg. 2. The reeds close when the magnet isbrought within one inch, and will remainclosed until the magnet has been moved atleast three inches away.

A typical example of this is shown inFig.2. In this example the reeds closewhen the magnet is brought withinone inch, but they will remain closeduntil the magnet has been movedabout three inches away.

This phenomena - which is causedby magnetic hysteresis in the reeds -can be considerably reduced by


Practical Guide to Reed Switches Part 1

introducing a second magnet, ofopposite polarity, on the further sideof the switch. This is illustrated inFig.3. The fixed magnet must not bemounted within the normal pull -inposition for single magnet operation,otherwise the reed switch will be heldin a closed position by the secondmagnet and will open when themoving magnet is brought close to theswitch. By selecting the correct typesand strengths of magnets thedifferential can be set to practicallyany required value.

N

S

MAGNET(FIXED)

S

N

MAGNET(MOVING)

Fig. 3. A fixed magnet of opposite polarityto the moving magnet may be used to reducepull -in, pull-out differential.

OPERATING MODESAs can clearly be seen in Fig.1, the

reed switch is 'normally open'. Thereeds close when a magnet is broughtclose to the switch enclosure.

However there are many applicationswhere the switch is required to be'normally closed' and to open whenthe magnet is introduced. This can bedone either by biasing the switch witha second magnet (as shown in Fig.4),or by using a reed switch withchange -over contacts (Fig.5).

In most applications where a reedswitch is opened or closed by a

permanent magnet, the magnet is

fitted to a moving part, and the reed isfitted to a stationary part.

There are, however, a number ofapplications in which both the magnetand the reed must be located on a

MAGNET

(FIXED)

Fig. 4. 'Normally closed' operation can beobtained by biasing a 'normally open' reedswitch with a fixed magnet. The movingmagnet cancels out the fixed magnet andthus allows the switch to open.

15

N

1 FLirlMAGNET(MOVING)

tiFig. 5. This type of reed switch may be usedfor either change -over, or normally closedoperation.

Tachometer applications, requiring thesimplest addition to the moving part andoffering ability to work in unfavourableconditions, plus high speed operation.

b'a

Fig. 6. Linear planes of operation; move-ment of the magnet in any of the planesindicated may be used to actuate the switch.

stationary component. Operation maythen be effected through distortion ofthe magnetic field by an externalmoving ferrous mass. If the magnetand the reed are sufficiently close, thereeds switch will be normally closed,but will be opened by the magneticshunting effect of the external ferrousobject. Alternatively, the magnet maybe located so that the reeds arenormally open and the externalferrous object used to 'reinforce' thefield and thus close the reeds.

There are many different ways inwhich a moving magnet may be causedto operate a reed switch.

Linear planes of operation are shownin Fig. 6.; movement of the magnet inany of the planes a -a, b -b, and c -c willoperate the switch. Magnet selection isfairly critical if the switch is operatedin mode b -b, spurious operation maybe caused by negative peaks on themagnet's field pattern curve. If theseare large, the reeds will pull -in threetimes as the magnet is moved from oneend of the switch to the other.

(C)

Rotary motion may also be used.Various ways of achieving this areshown in Fig.7. (A most versatile andsimple impulse generator can be puttogether in a few minutes by placingone or more magnets on a gramophoneturntable and fastening a reed switchto the motor base board. (Fig.8)..,Switching rates from approx one everytwo seconds to well over 2000 aminute can be selected merely bychanging the turntable speed and/orusing more magnets!)

Since the reed switch is truly a sealeddevice, it can be used in applicationswhere conventional switches are notpermitted, or where they have verylimited life. Reed switches arefrequently used in simple ,on/off pushbuttons, and outdoors, .in Asty areassuch as cement plants, especially inareas where explosive gases may bepresent.

(A)

Magnetic

shield cam

(CI)

/Magnets

(8)

Fled magnet

Magnetic

shield cam

Fig. 7. Rotary motion may also be used toactuate a reed switch. In A and B the switchesare stationary and the magnets rotate. Inexamples C and D both the switches and themagnets are stationary and the switchoperates whenever the cutout portion ofthe magnetic shield is between magnet andswitch.


The reed switch is functional andversatile. It is almost the simplestelemental form of switch and has innu-merable applications - from straight-forward functions in which switchactuation is initiated by the proximityof a permanent magnet - to complexlogic and computing functions, usinghundreds of electromagnetically drivenreeds. This practical three-part article,by Collyn Rivers, explains how andwhy they are used.

Flow control and indication, minimisingrestraint on the moving part and avoidingperforation of the container wall.

Position control and indication, obviatingmechanical contact with its implications ofwear, and simplifying mounting.

Door switches, obviating mounting andadjustment problems, and offering totalconcealment for security devices.

OPERATING LIFEThe operating life and load carrying

characteristics of reed switches areinterrelated. A switch may operate for100 million or even 1000 millionclosures providing it is switching very

low currents. But the same type ofswitch may fail after half a dozenswitching cycles if the ioad greatlyexceeds the designed rating. Themajority of reed switches aremanufactured with contact ratingsbetween 0.1A and 3.0A.

The current handling capacity ofreed switches varies from type to type.

In general the rating will bedetermined by the size and surfaceplating of the reeds, for the reed is an

Switching in explosive atmospheres, obviat-ing ignition risk; in dust filled atmosphereswhere conventional contacts would be un-reliable; and in extremely cold conditionswhere ordinary switches would freeze up.In radioactive environments, magneticoperation can maintain integrity of shielding.

J4 OPERATIONSPER REVOLUTION

TURNTABLE

Fig. 8. Simple yet versatile impulse timer canbe improvised by placing one or moremagnets on a turntable.

(A)

(B)

Load

C_

c

(C)R

I (-1Ye.C

(D) 01

Diode

Fig. 9. Contact protection techniques: A -Resistor shunting load. B - Capacitorshunting contact. C - Resistor -capacitorseries network for ac loads. D - Diodeshunting.



electrical conductor, and currentrating will be a function of contactarea.

The maximum rated contact loadingis only applicable for purely resistiveloads. If the load is capacitive orinductive the switch must either bedrastically derated, or the switchcontacts protected in a suitablefashion.

Four suitable methods of contactprotection are shown in Fig.9.

In dc circuits all that may berequired is a resistor shunted acrossthe load (Fig.9A). Where the load is arelay coil or operating solenoid a

resistor of approximately eight timesthe coil resistance is adequate toabsorb a major portion of the inducedenergy when the circuit is interrupted.The addition of the resistor will ofcourse increase the steady-statecurrent flow but this extra load is

negligible.Another cheap and simple way to

protect the reed switch is to wire acapacitor across the contacts. Therequired value depends upon loadcurrent, but something between 0.1 ufand 1.0 uf will be sufficient. (Fig.9B).The most generally used method of

protection is the resistor -capacitorseries network shown in Fig. 9C. Thiscircuit must be used if the switchedload current is ac. The resistor shouldbe approximately 160 ohms and thecapacitor somewhere between 0.1 ufand 1.0 uf. That this is an extremelyeffective method was proven by a

recent trial during which a motorstarter was switched 50 million timeswithout failure.

The component values may either bedetermined empirically (as describedbelow) or mathematically. In the latter

case, the component values can beobtained from -

C =12- /IF RE E2

10 10 x 1(140)

Where! is the closed circuit current inamps and E is the open circuit voltagein volts.A fourth method of protection is to

connect a diode across the switchcontacts. (Fig.9D). This method is

effective only with dc; diode polaritymust of course be preserved.

Suitable protection circuits are oftenbest determined empirically. One wayis to connect the switch to the normaloperating voltage and load, and thento actually observe the arcing acrossthe reeds while the switch ,s in use.

HEAVY CURRENT SWITCHINGThere will be many applications in

which a reed switch can usefully beused to switch very large currents. Thiscan be done quite simply bycombining a reed switch with a Triac.(Fig.10). Even miniature reed switches

SPECIFICATIONSMaximum voltage

Maximum currentMaximum powerMax. initial resistanceMax. end -of -life resistancePeak breakdown voltageClosure rateInsulation resistanceTemperature rangeContact capacitanceVibrationShockLife at rated loadLife at zero load

STANDARD150 Vdc250 Vac2.0A25W50 m.ohms2 ohms500 V400 Hz5000 M.ohms-55°C to +150°C1.5 pF10G at 10-55Hz15G minimum5 x 106 operations500 x 106 operations

MINIATURE50 Vdc150 Vac0.5A6W100 m.ohms2 ohms300 V2000 Hz1000 M.ohms-55°C to +150°C0.5 pF10G at 10-55 Hz15G minimum5 x 106 operations500 x 106 operations

Table 1.Typical specifications for standard and miniature reed switches.

Hydraulic brake fluid level indicator, wherefeasibility depends on simplicity and easecf application.

Fig 10. Reed switch/Triac combinationmay be used to switch single phase loads ashigh as 125 Amps. Components shown indotted lines must be included if the load isreactive.

Safety interlock switching, giving extremereliability and simplicity of application tocomplex mechanical layouts. Reed insertcompletes circuit to illuminate warning lampor permit further stage of operation.

will safely carry the gate currentrequired to trigger the largest Triacs,and by using this system it is possibleto switch single phase loads ofwhatever Triac rating is used. Triacscan be readily obtained with ratingsfrom 1 amp to 125 amps.

Three phase loads can also beswitched by using the reed switch toenergize a miniature three pole relaythat in turn triggers a Triac it each ofthe phases of the supply.

SWITCHING AT LOW LEVELS

One great advantage of the reedswitch is its ability to operate reliablywhen switching currents and voltagesat very low levels. This is a majorproblem with standard switchesbecause there is insufficient energy tobreak down non -conducting films onthe switch contacts. But a reed switch- due largely to its gold-plated contactsurfaces and inert atmosphere - willperform satisfactorily for at least abillion operations.



IIII

IIII LARGE (40") MEDIUM (37") SMALL (34")

ri Number Ft Number El Numberrequired LJ required LI required

Some idea of the extraordinaryreliability of reed switches was shownduring a series of tests undertaken bythe Bell Telephone Company in theUSA. In one test four switches wereoperated at 120 closures a secondcarrying a load of 500 micro -volts, 100microamps, dc. Each switch completed50 million consecutive closureswithout a single instance of closedresistance exceeding 5 ohms.

FAILUREA reed switch rarely fails completely.

As load currents are increased thecontacts suffer the same form ofcontact erosion experienced inconventional switches. The resultant

particles are magnetic and collect inthe air -gap. If these fragments become

Proximity counting, providing a very easymethod of recording the passage of ferrousitems past a point.

numerous enough they intermittentlybridge the gap and cause a

failure -to -open. It is also possible forthese fragments to alter the closedcontact resistance.The most common cause of contact

failure is the mechanical locking of aspike on one reed and a correspondingcrater on the other. This type offailure is commonly called a 'weld' butit is not a weld in the true sense. Thecontacts are not joined by moltenmetal but are held by friction orinterlockingi between the spike andthe crater.

NEXT MONTHThe second part of this article, which

will be published next month, willdescribe applications in which reedswitches are electrically energized.

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Brains and

ComputersMan is just a machine, or is he? Is his brain the ultimate mechanism or couldit be improved by bio-engineering techniques? How can we develop artificialintelligence to match the abilities of our own brains and what do we have tolearn from it? By S. Mc Clelland.

EVEN IF THE HUMAN BRAIN is regarded as being adigital computer it must be considered to be far morecomplex than anything man can devise - or is likely todevise in the foreseeable future. In a volume of tissuefar less than that of a football it packs some 1010 (that's10 000 000 000) active elements, the nerve cells. Incomputer terms, its capacity to store information mustrun onto the 10 thousand megabit range at least.

Its organisation matches its abilities - on average ina normal human being it's been estimated that 1 nervecell dies every 10 seconds throughout our lives. It isnever replaced, for brain cells alone in the body cannotreproduce, and yet we never notice the loss since thebrain is so well organised that many of its circuits areredundant and can be replaced by alternative channelsshould they fail - this has been the case even afterserious injuries have been inflicted on the brain.

How much power does all this require? It's enough tomake an engineer cringe -a meagre few watts!

What about the brain's higher capabilities - such asits capacity for inventiveness or 'original' thought? Whatwas special about Mozart's brain circuits that enabledhim to start composing music before he was 5 years old,or in Leonardo da Vinci's case, to design flying machines500 years ahead of his time?

Sadly as yet we have no idea since so little is knownabout the brain!

INPUTS AND OUTPUTS

All this uncertainty has not stopped a growing number ofsystems engineers and scientists from looking at thebrain's organisation and operation (possibly with theidea of wanting to copy techniques in future systems!).

We can certainly find some aspects of central nervoussystem operation in common with computers. Bothsystems have of course what might be loosely termed'input' and 'ouput' peripherals, for example. In the caseof the brain the inputs are from the senses of the body,not only the primary ones of sight, hearing, smell andtaste but also from many thousand of receptors near thesurface of the body for various parameters such astemperatures and pressure.

Its outputs go to activate all the muscles in the body.This flow of information demands an enormous numberof nerve fibres to convey it - up to a million nerve fibresare estimated to be associated with each major limbalone

All of this of course prompts the question. "How doesthis information transfer take place?" To understand thiswe have to look at the most basic component of thewhole system - the nerve cell itself.

NEURONS

If we could remove a typical nerve cell from our bodiesand look at it under a high power microscope, it wouldlook something like Fig 1 . Remember, this cell isprobably only a few micrometres in diameter so whatwe're about to describe is a microscopic system -within -a -system .

The cell picks up signals from the other cells in itsvicinity and these are fed down to the main part of thecell (containing the nucleus) and propogated along thelong transmitter branch (axon) to the next cell.

It's along the inside of these long membranousETI CANADA-JULY 1979 49

FRONT

MOTOR AREA -CONTROLSLIMB MOVEMENT

SPEECHAREA

CEREBRUM -MAJOR PARTOF BRAIN

VISUAL AREA -PROCESSESINFORMATIONFROM THE EYES

REAR

CEREBELLUM -CONTROLS MUSCULARCOORDINATION

BRAIN STEM--- (LEADING TO

SPINAL CORDI

This is what your CPU looks like with the cover off. Note the I/Obus at the bottom (not S-100). The power supply connections havebeen omitted for clarity. The case is of a sturdy polymeric materialand the main PCB fits it nicely.

branches that the electric impulses (or action potentials)are transmitted by the nerve.

The axon is no mere passive wire, however. If it was,the signals would soon be drastically attenuated by theleakage of the membrane to the outside after a very shorttravel. The cell membrance instead acts as its own signalbooster to maintain the impulse at constant amplitude(about 100 mV) at any point on the axon. The actionpotential is either there or it isn't - there is no in-between state. A digital system? Perhaps. In fact, it's thefrequency at which the action potentials are signalledthat carries the information. We can now see why somany nerve fibres are needed to carry information. Eachcell - and probably many others for the sake of re-dundancy - carries one 'bit' of information. The import-ance of this information depends on the frequency it isbeing signalled and it is likely that a high frequencysignal establishes a higher priority than a lowerfrequency signal in a particular context - rather likesignalling an 'interrupt' in a computer system.

Simnle as it is, a frequency -dependent system carriestt own problems. The sense organs must make

amplitude -to -frequency code conversions for transmis-sion down the fibre and at the other end, the brain mustfind a way of coping with a frequency -dependent signal.

A secondary point is that all the nerve cells concernedwith a particular function or sub -function work inparallel. The advantages of parallel processing are fairlyevident. It's faster than serial and has a higher signal-to-noise ratio (even if it does need more channels).

So we can visualise action potentials - small spikesof voltage - being flicked up and down all the nervefibres in the body at varying frequency, but not nearly asfast as electrical impulses through cables. However,even in this, nature squeezes all the performance it canout of the human nervous system. Each nerve cell iswrapped in several layers of fatty tissue with nicks'

or 'breaks' in the fat at intervals along the axon. Theeffect of these 'breaks' or 'nodes of Ranvier' as they areknown is to increase the speed of transmission of theaction potentials down the nerve axon to about 100metres per second.

DELAYING TACTICS ANDLOGIC GATES

If neurons propagate the action potentials, then its thejunctions between neurons (synapses) that route them.It's the synapses which work out if the incoming signalsare of the right type and frequency to trigger thefollowing cell to produce an action potential. From thepoint of view of the system, the synapses are the delaylines, one-way valves, triggers and gates all rolled intoone.

It takes an electron microscope to even see thesynapse regions and even then they don't look veryspecial - they're merely bulbous terminations wherenerve cells meet each other. Except that they don't meeteach other - they're always separated by the absolutelymicroscopic distance of about 200 A - so the actionpotential never gets across even the gap, let alone downthe other side.

What actually crosses the gap is not the electric signalitself but very small quantities of hormones which arereleased from the transmitter bulb. The hormone crossesto the receptor membrane where (by a process that's notfully understood) it causes the generation of anotheraction potential. Even across so small a gap the chemicaltransmission takes a finite time and is susceptible tointerference by foreign chemicals (drug addicts pleasenote - your synapse may be switched off!).

Some synapses, instead of generating an action.potential in the receptor membrane actually inhibit itfrom doing so - so we've found the on -off switches forthe nervous system. Can we identify Boolean logicgating arrangements in the nervous system? It's pos-sible to speculate in those terms and certainly the basicmechanisms seem to be there, but unfortunately notenough is known about even simple neuron groups topermit an answer to this question.

DON'T BELIEVE YOUR EYES!The nervous system can do some very sophisticatedthings to the input signals it receives by way of dataprocessing. It can, for example, selectivity inhibit thetriggering of neurons that carry no useful information infavour of ones that do.

This so-called 'lateral inhibition' not only cleans uppotentially noisy channels by making them more 'con-trasty' but in some animals is known to help the eyeresolve very efficiently the boundaries between dark andlight edges in an image. It probably occurs in the humannervous system as well where it is thought to give rise tosome of the more common optical illusions as a by-product.

So much processing sophistication backing up thesenses means that the brain can work on far less sensoryinformation than it usually gets. For example, the brainreally only requires a few per cent of the data it receivesfrom the eyes in order to form a valid judgement as to thenature of the image. The same applies to the ear -speech has to be very badly distorted before the braincannot recognise it. There is obviously a very close and


Brains and Computerscomplex interaction between the senses and thememory, which is continually generating possible 'best -fit' models to match the latest information received.Each model is discarded until the brain is satisfied withthe result.

Our senses show a fantastic sensitivity to the worldaround us - we can hear a pin drop in a quiet room.More staggering still, the vibration amplitude of the eardrum which the minimum audible sound creates is lessthan the diameter of one hydrogen atom . . .!

DOWN MEMORY LANE

Digital computers have clearly -defined memory loca-tions which are usually addressed under the control of aclocked pointer in the system. The human brain on theother hand seems to have no all-powerful organ ofmemory - attempts to find one have so far provedinconclusive. Rather, memory is a property of the systemas a whole.

Secondly, data storage on a computer tape or disc ispermanent until deliberately erased but information flowthrough the brain is far more dynamic and its retentionmore selective. Information floods into our brains fromour senses at every living moment. Seen in this light it isneither desirable nor even possible to store it all. 'Storeonly the information that is important' the brain says toitself - but what is counted as being important?

Basically, we pick out the information about thechanges in our environment, because it's the changes init which may be threatening our immediate survival.

On a motivated level, we can store items deliberately.We remember by repetition (e.g. a telephone number).Most importantly we store information which isassociated with something which has caused us greatpain or pleasure in the past. How do we recall informa-tion once stored? It's clear that association plays acritical role. After all, we store not isolated events butconnected ones - 'trains of thought' if you like. Thememories are recalled when the right key of stimulus isprovided. This stimulus may well be a piece of informa-tion associated with the group.

For example, the question "What do you rememberabout November 22nd 1 963?" would probably elicit ablank reply from most people until (as various commen-tators have pointed out) that they are told its the daywhen the President John F. Kennedy was assassinated.Many people can recall where they were or what theywere doing - it's a memory that persists over 15 yearsbecause it is associated with such a traumatic incident.

In this way we can visualise the human memoryalmost as 'conglomerates' of memories - pieces ofinformation tied together in some fashion only requiringthe right input trigger to push it all out.

Some very intriguing hypothesis about how the' memory operates have been suggested. One excitingand topical suggestion is that it records information as ahologram records 3-D images in laser light. A particularpart of the image is not localised to a particular part ofthe hologram - in fact even a fragment of the hologramcan theoretically recreate the entire image, a propertywhich makes it very similar to the brain.

We must wait for more basic information on the brainto confirm or disprove this.

RECEIVING BRANCHES !DENDRITES?, OF SIGNALS FROM OTHER NERVE

CELLS NEURONS? SHOWN DOTTED

'BREAIC IN FAT,NODE OF RANVIERI

INSULATING FAT

INTERIOR OF NERVE CELLI 1 000,000010

110 .1

BRANS

INSLILATINGFAT '

MAIN CELL BODY

AXONMAJOR TRANSMISSIONBRANCH,

32g47 RgNVIERI

1114/A:11, TO NERVE OF MUSCLE

Figure 1: What a nerve! A typical nerve cell examined.

TUNING INTO BRAIN WAVESWe can get some idea of what all this electricalactivity is like by strapping electrodes - connected to asensitive amplifier and chart recorder - to the skull.

We will obtain a rather confusing output of signals -referred to as an electroencephalogram or EEG. The EEGis usually a very weak signal - a few tens of uVamplitude at a range of frequencies mostly under 30 Hz,although higher frequency components are present.

The most well-known component of the EEG is thea -wave. Present in about 90% of all individuals, thissignal (with a frequency between 8 Hz and 13 Hz) is at itsmost active when the subject is relaxed and his eyesclosed. It disappears as soon as the subject opens hiseyes or starts to concentrate on something like mentalarithmetic.

What does it mean? Basically, we don't know. Nor dowe know where or how it's generated, although itssource (there may be more than one) seems to be locatedto the upper rear of the brain. Correspondingly little isknown about the other EEG components.

Although the EEG doesn't give a great deal of infor-mation about the working of the brain (indeed we'llprobably have to wait until further studies of the brainexplain the EEG!) it has found great use in diagnosis ofbrain disorders such as epilepsy. But could the EEG havea more fundamental significance than that? My ownpure piece of speculation - for what it's worth - is thatit's the brain's clock, although it's too low in frequencyto cope with many of the fast muscular actions of thebody. Even so the 'ticking' of a brain might have abiological significance similar to a digital system's 'clockfrequency"!FURTHER READING: For those who would like to readmore fully about the brain, Professor Steven Rose's book"The Conscious Brain" (Penguin paperback offersa very readable account.


Op Amps: Part 3Op Amps are are some of the most useful devices since the wheel was discovered.Our series of handy circuits continues .

SIMPLE MUSICAL ENVELOPE GENERATORA simple generator can be constructed using the CA3080(made by RCA). This circuit will also enable the use of an 39k

.I5V

audio waveform the harmonic structure of which will not be v'" V OUTsignificantly affected as it is modulated. The CA3080 is an 6

op amp with a difference. It has a current output and an extrainput into which a current, IA is fed. The output is the 39k

product of the input voltage X IA. Thus the IA can be used to PRESS TO

control the amplifier's gain. ENVELOPEThe input voltage range for low distortion operation is

very low, of the order of ± 25 mV.The CA3080 is being used as a two -quadrant multiplier. A

small voltage, (± 25 mV), is applied to its non -inverting input.When the switch S1 is closed, the capacitor C is charged upand a current of about 150 µA flows into the IA input term-inal. When S1 is opened, C discharges through the 150 kresistor into the IA input. This current dies away exponentially. an exponential envelope is generated. Breakthrough after theAs the output is the product of the input voltage X IA, then decay is very good, better than -80 dB.

VARIABLE MARK -SPACE SQUARE WAVEGENERATOR WITH AUTOMATIC LEVEL ADJUST

By putting a triangle wave into one input of a comparatorand a manually controlled DC level into the other, it ispossible to generate a variable ratio mark/space squarewave. However, if the amplitude of the triangle variesthen so will the markspace ratio. Alternatively, if youwant the manual control to produce a very thin waveformat one end of its travel, then you will probably need apreset and a very stable triangle amplitude. Howeverthis circuit solves these problems. The DC voltage is gener--ated by a peak voltage follower, IC1, driven by the triangleitself. Thus the circuit tracks the peak voltage level. second-ly, only 97% of this voltage is ever fed to the comparator,IC2, and so at the end of the markspace pot, a 60:1 ratiopulse train is generated. At the other end of the pot theratio is 1:1. A 748 is used as the comparator because ithas more bandwidth than the 741. As the frequency ofthe triangle increases, it may be necessary to use an evenfaster op -amp for IC2, or even a comparator.


Op Amps: Part 3

.1.

22k

2V

-1.75V

10k

D1

.1.75V47k

01. 02 . 119914

-2V

SIMPLE TRIANGLE TO SINEWAVE CONVERTERHere is a simple way of converting a triangle to a sinewave.The logarithmic characteristic of the diodes is used to approx-imate that of a sine curve. Distortion is 5% or so. However, thedistort on may be tolerable if the sinewave is only used togenerate audio tones.

NOISE GENERATORThe zener breakdown of a transistor junction is used in manycircuits as a noise generator. The breakdown mechanism israndom and so generates a small noise voltage. Also this volt-age has a high source impedance. By using the op -amp as ahigh input impedance, high ac gain amplifier, a low imped-ance, large signal noise source is obtained. The preset is usedto set the noise level by varying the gain from 40 to 20 dB.

100k SET LEVEL

RANDOMNOISE

LOGARITHMIC VOLTAGE TO VOLTAGE CONVERTERThe output voltage is logarithmically proportional to the inputvoltage. The difference between this circuit and the followingis that the exponentiator is in the feedback loop of the op -ampand hence the mathematical function has been inverted. Thecircuit is useful for performing true logarithmic compressionor for converting linear inputs into dBs.

lk

EXPONENTIAL VOLTAGE TO CURRENTNOLTAGECONVERTERThe circuit shown converts a linear input voltage into anexponential current or voltage. This type of circuit is used inmusic synthesisers to change linear control voltages intomusical intervals. That is, if the circuit were used to controlan oscillator, input increments of 1 V would change the pitchby one octave. The exponential characteristics of a transistorare exployed to generate the correct transfer function. Q1 and12 are matched pairs of transistors, preferably a transistor dual.IC1 maintains 01 at a constant current. Thus, the op -ampserves only to bias the emitter of the second transistor Q2 intoa suitable operating region. The purpose of Q1 is to generatethis bias voltage. The base emitter junction of a transistor


V OUT

v IN

1V/OCTAVE

has a high temperature coefficient (-1.9 mV/°C) and so thereason for using a matched pair is to use the first transistor,01, to provide temperature compensation for the second.

53

Op Amps: Part 3

47

.10yOFF ON. OFF

OV

GATE M ATTACK

M DECAY

47k

OUTPUT ENVELOPE

00

OUTPUT0

.10y

01PNP

02NPN

1JTED

4u7

1604

10kTONEINPUT

OV

MUSICAL ENVELOPE GENERATOR AND MODULATORA gate voltage is applied to initiate the proceedings. When thegate voltage is in the ON state, Q1 is turned on, and so thecapacitor C is charged up via the attack pot in series with the1 k .resistor. By varying this pot, the attack time constant canbe manipulated. A fast attack gives a percussive sound, a slowattack the effect of 'backward' sounds. When the gate voltagereturns to its off state, Q2 is turned on and the capacitor isthen discharged via the decay pot and the other 1 k resistor,to ground. Thies the decay time constant of the envelope isalso variable.

This envelope is buffered by IC1, a high impedance voltagefollower and applied to Q3 which is being used as a transistorchopper. A musical tone in the form of a squarewave is con-nected to the base of Q3. This turns the transistor on or offand thus the envelope is chopped up at regular intervals, theintervals being determined by the pitch of the squarewave.

The resultant waveform has the amplitude of the envelopeand the harmorvc structure of the squarewave. IC2 is used as avirtual earth amplifier to buffer the signal and D1 ensures thatthe envelope dies away at the end of a note.

V IN«V

DIGITAL ON//OFF CONTROL

(ON)OV

ID

+VE(OFF)

R2100k

R510k

R1100k

ADJUST"OFF"

R4100k

01PNP

100nOUT

47k

TRANSISTOR USED TO TURN AN OP AMP ON OR OFFWhen transistor Q1 is switched off, the circuit behaves as avoltage follower By applying a positive voltage to the emitterof 01 via a 10 k resistor, the transistor is made to turn on andgo into saturation. Thus the lower end of R4 is shorted toground. The circuit has now changed into that of a differentialamplifier (see fig. 7), but where the voltage difference is always0 V. Now as long as the resistors in the two branches aroundthe op amp are in the same ratio then there should be zerooutput. A 4k7 preset is used to null out any ratio errors sothat the 'OFF' attenuation is more than 60 dB. The highcommon mode rejection ratio of a 741 enables this largeattenuation to be obtained.

FAST SYMMETRICAL ZENER CLAMPINGThere are several problems with using zeners, back to back inseries to get symmetrical clamping, the knee of the zenercharacteristics is rather sloppy, charge storage in the zenerscauses speed problems and the zeners will have slightly dif-ferent knee voltages so the symmetry will not be all thatgood. This circuit overcomes these problems. By putting thezener inside a diode bridge the same zener voltage is alwaysexperienced. The voltage errors due to the diodes are muchsmaller than those due, to the zener. Also the charge storageof the bridge is much less. Lastly by biasing the zener on allthe time, the knee appears to be much sharper.

V IN

47k

1N914 3k3 +15V

1N914

1N914

1N914-15V

3k3

V OUTVz + 1.2V

(MAXIMUM OUTPUT)


NEW LOW COST LX303 DMM

HICKOKthe value Innovator

$99.95Operates up to 200 hours on a single 9volt battery. 100 mV DC f.s. sensi-tivity. Features auto zero, polarity,overrange indication. Nineteen rangesand functions. With easy -to -read 1/2"

LCD display for convenient use

in any kind of light. Removeablecover stores test lead set furnishedas part of the unit. Excellent overloadprotection. Colour coded panel. Car-ries a full one year warranty. Avail-able accessories include 10 kV probe/adapter, 40 kV probe, 10 amp DCshunt, AC adapter and deluxe paddedvinyl carrying case.

Duty and FST included.Chargex (Visa accepted.Ont. res. add 7% sales taxF.O.B. Ajax.

N

SPE:C.11.1CA NUNS:

DC VOLTS (5 RANGES): 0.1mV to 1000V; Accuracy ±0.5%rdg ±0.5% is.; Input imped: 10Mohm; Max. input 1kV except 500Von 200mV range. AC VOLTS (40Hzto 5kHz): 0.1V to 600V; Accuracy:±-1.0% rdg -±0.5%f.s. (-2db max. at5kHz); Max. input: 600V.

RESISTANCE (6 LOW POWERRANGES): 0.1 ohm to 20M ohm;Accuracy: -±0.5% rdg ±0.5% f.s.(±1.5% rdg on 20M ohm range);input protected to 120 VAC allranges.

DC CURRENT (6 RANGES): .01nAto 100mA; Accuracy: ±-1.0`/. rdg

f.s.

DIMENSIONS AND WEIGHT:5-7/8" x 3-3/8" x 1-3/4", 8 oz.;POWER: 9V battery (not included)or Hickok AC adapter; READRATE: 3/sec.

ROGERS electronic Instrument/ ltd.P.O. Box 310, 595 Mackenzie Avenue Units 1 & 2.Ajax, Ontario L1S 3C5. Tel. (416) 683-4211

MORE CIRCUITCircuits to get you thinking howto solve your special tasks, orjust for fun. From power controlsto special effects to alarms, testcircuits, and so on. Plus detailedsections on crystal oscillators,speaker crossovers and more. Forordering details see below.

Obtain yours now from us directly by using the order card in this issue, or by mai mg $4.50 + 45c for postage and handling toMORE CIRCUITS, Electronics Today Magazine, Unit 6, 25 Overlea Blvd, Toronto, Ontario, M4H 1B1. Or if your local magazineshop has ETI regularly, they'll be getting MORE CIRCUITS too.

Bingo!Let your T159 call the numbers, so you can win! From Donald Lessard.

THIS PROGRAM is written for theTI 59 with or without the PC -100Aprinter. It works like real bingo. Thenumber (chosen at random) drawn isprinted or displayed. It can be chosenonly one time in a game. The seednumber determines the numbers drawn,which means that you can have 199017different games of bingo.

After you load the memories (youneed 90 memories to run the program.That's why it is suitable for TI 59owners) and enter a seed number,pressing R/S causes the calculatorto print or display a number. Each timeyou press R/S another number isprinted or displayed. And each timethe contents of( the memories wherethis number was kept is replaced by 0.That's why when you want the listof all the numbers not drawn, the cal-culator prints or displays only thenumbers which are in memory.

This program can be played without

make are: 1) load the memories withnumbers from 1 to 75 starting atmemory 12 which will be loaded with I,memory 13 with 2 etc. 2) Key in theprogram without the printer. 3) Allthe operations are the same. Naturallyyou won't have the letters printed,so you will have to know that numbers1 to 15 are for the letter B, 16 to 30for letter I, etc. 4) You can have alist of the numbers not drawn. Thecalculator, after pressing B, will flashfor about 2 seconds each number nottaken.

Naturally, each time you want toplay another game, you have to reloadthe memories. This is easy with theTI 59 because you've recorded theprogram and the memory contentson two magnetic cards. You have toremember that the calculator must bepartitioned in 90 memories. So beforereading or recording the calculator,you have to press 9 of 17.

EXECUTION1) Key in: 9 of 17. Display: 239.892) Key in the numbers to be put in

memories 12 to 86.3) Key in "Learn": Enter the program:

Key in "Learn" to exit.4) Now you can record the program and

the content of the memories on twomagnetic cards by pressing: 1 SNDWRITE and 2 SND WRITE on onecard and 3 SND WRITE and 4 SNDWRITE on the other card.

5) Enter seed number (0 < SEED199017) by pressing "A": dis-

play: 0.6) Press "R/S" each time you want a

new number. With the printer: Thenumber will be printed and the dis-play: 0.

6) Press "R/S" each time you want anew number. With the printer: Thenumber will be printed and the dis-play will show how many numbersthe printer. The changes you have to

fig.2. If you don't own aprinter then try this ver-Ou

00136 PGM041042

0144

1

SUM080081

3615

PGM15 sion. 14000200.

14000300.1213

31000502.31000503.

525302 15 043 88 88 082 12 B 14000400. 14 31000504. 54003 13 C 1.144 00 0 083 01 1

14000500. 15 31000505. 55004 42 STO 045 32 X:T 084 04 4 000 91 R/S 042 36 PGM 14000600. 16 31000506. 56005 88 88 046 73 RC* 085 Cr, 2 001 36 PGM 043 15 15 14000700. 17 22000507. 57006 00 0 047 88 88 086 04 4 002 15 15 044 12 B 14001000. 18 22000510. 58007 32 X:T 048 67 EQ 087 03 3 003 13 C 045 00 0 14001100. 19 22000511. 59008 73 R0* 049 00 00 088 01 1 004 42 STO 046 81 RST 14001200. 20 22000512. 60009 88 88 050 41 41 089 69 OP 005 88 88 047 76 LBL 14000201. 21 22000601. 61010 67 EQ 051 69 OP 090 02 02 006 00 0' 048 12 B 14000202. 22 22000602. 62011 00 00 052 02 02 091 02 2 007 32 X1T 049 07 14000203. 23 22000603. 63012 01 01 053 69 OP 092 02 2 008 73 RC* 050 05 5 14000204. 24 22000604. 64013 69 OP 054 05 05 093 03 3 009 88 88 051 75 14000205. 25 22000605. 65014. 00 00 055 97 DSZ 094 02 2 010 67 EQ 052 43 RCL 14000206. 26 22000606. 66015 69 OP 056 00 00 095 00 0 011 00 00 053 08 08 24000207. 27 22000607. 67016 02 02 057 00 00 096 00 0 012 01 01 054 95 24000210. 28 22000610. 68017 69 OP 058 41 41 097 00 0 013 42 STO 055 42 STO 24000211. 29 22000611. 69018 05 05 059 00 0 0.98 00 0 014 $7 $7 056 00 00 24000212. 30 22000612. 70019 69 OP 060 81 RST 099 00 0 015 69 OP 057 01 1 24000301. 31 22000701. 71020 28 28 061 76 LBL 100 00 0 016 28 28 05$ 01 1 24000302. 32 32000702. 72021 00 0 062 11 A 101 69 OP 017 00 0 059 42 STO 24000303. 33 32000703. 73022 72 ST* 063 42 STO 102 03 03 018 72 ST* 060 88 88 24000304., 34 32000704. 74023 88 88 064 87 87 103 69 OP 019 88 88 061 01 1 24000305. 35 32000705. 75024 43 RCL 065 36 PGM 104 05 05 020 43 RCL 062 44 SUM 24000306. 36 32000706. 76025 08 08 066 15 15 105 00 0 021 87 87 063 88 88 24000307. 37 32000707. 77026 81 RST 067 10 E' 106 98 ADV 022 81 RST 064 00 0 24000310. 38 32000710. 78027 76 LBL 068 4:3 RCL 107 81 RST 023 76 LBL 065 32 X:T 24000311. 39 32000711. 79028 12 B 069 87 87 024 11 A 066 73 RC* 24000312. 40 32000712. 80029 07 7 070 36 PGM 025 42 STO -067 88 88 24000401. 41 32001001. 81030 05 5 071 15 15 026 87 87 068 67 Et) 31000402. 42 32001002. 82031 75 - 072 15 E 027 36 PGM 069 00 00 31000403. 43 32001003. 83032 43 RCL 073 01 1 028 15 15 070 61 61 31000404. 44 32001004. 84033 08 08 074 02 2 029 10 E' 071 66 PAU 31000405. 45 32001005. 85034 95 = 075 36 PGM 030 43 RCL 072 66 PAU 31000406. 46 32001006. 86035 42 STO 076 15 15 031 87 87 073 97 DS' 31000407. 47 O. 87036 00 00 077 11 A 032 36 PGM 074 00 00 31000410. 4$ 0. 88037 01 1 078 08 8 033 15 15 075 00 00 31000411. 49 0. 89038 01 1 079 07 7 034 15 E 076 61 61 31000412. 50039 42 STO 035 01 077 81 RST 31000501. 51040 88 88 036 02 2

037 36 PGM

fig.1. Bingo program foruse with PC100A printer.

038 15039 11040 08041

15A

fig.3. Memory initializa-tions required before run-ning. Store this on cards.

56ETI CANADA -JULY 1979

ETI Soffspot

FLOW CHART

YES

Recall Pgm 15To Generate NumbersBetween 12 and 87

Put the number

in the memory

Recall indirectMemory

(Print that number

Clear the contentof the memory ofthe number printed

rofAdd 1 to counternumbers printed

Display Countof Numbers Printed

NO

Print That ListYES

YES

fig.4. Sample game (withseed number 123), first 42numbers drawn. b) remain-ing numbers available.c) what memory looks likeduring a game.

a) e INGO

N 39I 30I 17N 3,C 60G 54N 32G 598 30 660 65I 24N 36N 44I 21B 130 6!o 62I 16I 25N 3i0 68G

I 188 413 7G 53G 58G 558 6O 75G 50 9G 51B 158 8N 450 73

1:18 5G 46N 35

b) 6 1

E: 2B 118 12B 14I 19I 20I 22I 23I 26I 27I 28I 29N 33N

N 28N 40N 41N 42N 43G 47G 48G 49G 52G 56O 630 640 67O 69O 70O 71O 72O 74

have been drawn. Without theprinter: The number will be dis-played.

71 Press "B" each time you want alist of numbers not drawn. If youwant another number after that,just press "R/S" and the calculatorwill print or display another lumber.

FLOW CHARTSYMBOLS

/

O

0

Information Output

Data to be Input

Branch

Operations

Program Entry Point

End

c) 14000200. 12 0. 5014000300. 1:3 31000501. 51

0. 14 31000502. 520. 15 31000503. 530. 16 31000504. 540. 17 0. 550. 18 0. 560. 19 0. 570. 20 22000510. 580. 21 22000511. 59

14000202. 22 22000512. 60141000203. 23 0. 61

0. 24 0. 6214000205. 25 22000603. 6:3

0. 26 0. 640. 27 0. 650. 28 0. 660. 29 22000607. 67

24000212. 30 0. 6824000301. 31 G. 69

0. 32 C1. 7024000303. 33 0. 7124000304. 34 O. 72

0. 35 0, 730. 36 32000704. 74

24000307. 37 32000705. 7524000310. 38 O. 7624000311. 39 0. 7724000312. 40 32000710. 78

0. 41 0. 790. 42 32000712. 800. 43 32001001. 81

31000404. 44 32001002. 820. 45 32001003. 830. 46 0. 840. 47 32001005. 85

31000410. 48 O. 8631000411. 49

ETI CANADA -JULY 1979 57

ETI Soft pot

Ohm's LawMade FoolproofProgrammable number crunching of this fundamental equation. By Rob Ings.

THIS PROGRAM is especially usefulfor those people who are not yetcomfortable with Ohm's Law, or forthose who have a lot of network pro-blems to solve. In either case thisprogram will take the values you haveand return the unknown variable.

Known numerical variables are load-ed into memory before execution,the unknown variable being assigneda value of zero. By a series of testsfor zero the program determines whichis the unknown and then performs theproper calculation. The final resultis displayed (the idea of identifyingan unknown by assigning it a zero is

very useful for general purpose pro-grams).

You might want to modify the inputformat of this program. Try for in-stance, assigning labels for each of thevariables, or have the program callfor the values when it is running.

The program listing given was writtenfor a TI 57, but it can be adapted withvery little difficulty to any of the TIprogrammables. Of course the fund-amental algorithm can be applied toany programmable calculator.

ERRATA: In our May issue, the TrigIn Feet, Inches and Fractions programhas an error in it. After step 135, inserta CLR instruction after the STO 2 inst-ruction.

In the June issue readers may be sur-prised to see half a program. That'sbecause we couldn't decide whether toput it in or not, and in the end therewas an accidental compromise! Readerswishing a copy of the entire programmay write in for the whole thing, pleaseenclose a stamped, self addressedenvelope.

All programs we publish will be paidfor.

Mail to: ETI SoftspotUnit 6, 25 Overlea Blvd.,TORONTO, OntarioM4H 1 B1

00 33 1 RCL 101 22 X<->t02 15 CLR03 33 6 RCL 604 66 2nd X=t05 51 1 GTO 106 33 2 RCL 207 22 X<->t08 15 CLR09 33 6 RCL 610 66 2nd X=t11 51 2 GTO 212 33 1 RCL 113 5514 33 2 RCL 215 8516 81 R/S17 86 1 2nd Lbl 118 33 3 RCL 319 4520 33 2 RCL 221 8522 81 R/S23 86 2 2nd Lbl 224 33 3 RCL 325 4526 33 1 RCL 127 8528 81 R/S

RCL 1 'resistance'RCL 2 'amperage'RCL 3 'volts'

EXECUTIONeg. R=3 ohms

A=40 ampsV=?

Key into memory;340

III 0

RSTR IS

The display will read 120(120 volts). To use again, keyin INV 2nd CT & repeat.

MultiplyResistancebyAmperage

DivideVoltageby Resistance

Yes

Yes

DivideVoltageby Amperage

DisplayNumber


Shortwave World

SWL Via

IonosphereThe ionosphere affects the way in which the signals get to your set. John Garnertells why, and what it sounds like.

HOW SHORTWAVERADIO SIGNALS TRAVELAROUND THE WORLDNEAR THE EARTH the air is ratherdense, but from above one hundred toone thousand kilometres (60 to 600miles) above the earth the air is quite thinand radiated energy from the sun canionize the widely spaced air molecules.This layer of the atmosphere is called theIONOSPHERE. The different degrees ofionization produced form into severalrecognizable layers. The ionized atmo-sphere allows the radiated wave to travelfaster through it than in the more dense,un-ionized lower air. As a result, the toppart of a wave front moving into the iono-sphere speeds up and forges ahead ofthe lower part of the wave front andeventually may turn, or refract, the wavedownward.

The lower the frequency of the waves,the less penetrating effect they have andthe greater the proportion of them thatmay be turned back toward earth. Thehigher the frequency, the more penetrat-ing energy the radio wave contains. Sig-nals with frequencies of 10 to 30megahertz may be deflected, or theymay penetrate the ionosphere, depend-ing on the time of day, the angle at whichthe wave strikes the ionosphere, and thedegree of ionization present. With weakionization they penetrate; with strongerionization they may be refracted. Withstill stronger ionization the wave energymay be totally absorbed and dissipatedin the ionosphere.

During times of sunspot activity andwhile the aurora borealis is active, ioni-zation is considerably increased and

long-distance transmission may beinterrupted because of almost completeabsorption of all waves by the iono-sphere.

Besides the frequency factor, theangle at which the radio wave enters theionosphere determines the penetrationor refraction of the wave. While theremay be some reflection of lower -fre-quency signals travelling directlyupward, almost all higher -frequencywaves that are transmitted at an angle ofnearly 90° above the surface of the eartheither penetrate or are absorbed by theionosphere. As the angle becomes lessthan 90°, there is more chance of refrac-tion. The higher the frequency, thegreater the penetration and the lower theangle required to produce refraction. Athigh frequencies, there may be long dis-tances between the end of the usableground -wave signal and the reappear-ance of the reflected wave. At lower fre-quencies the sky wave often returns toearth in the ground -wave region.

If the sky wave returns to earth andstrikes a good conducting surface suchas salt water, it will be reflected backupward and take a double hop. A doublehop may carry a signal a very longdistance.

FADINGThe fading of signals stems from twomajor causes. If a sky wave is beingreceived, variations in the ionospheremay refract more or less energy to anygiven receiving point at differentinstants, producing a varying amplitudeor fading signal.

When the receiving antenna is withinboth ground and sky wave range, the

addition of the two waves may be in orout of phase. When arriving in phase, thewaves add to each other, producing astrong signal. When out of phase 180°,they tend to cancel each other. Varia-tions in the ionosphere can change thesky -wave travel distance and thereforethe phase relationship of the ground andsky waves. The sky waves refracted tothe same point by two different areas ofthe ionosphere may arrive in or out ofphase and produce fading.

LIGHTNINGA bolt of lightning produces RF energyacross almost the whole usable radiospectrum, but the percentage of energydecreases as the frequency increases. Atlower frequencies there is considerableenergy, and with good ground -wavetransmission, storms hundreds or thou-sands of miles away can produce con-siderable interference. The higherfrequencies, particularly between 5 and15 megahertz, are subject to localstorms, but storms in the skip zones willnot be heard. As a result, the higher fre-quencies are much less subject to light-ning -produced radio noise, called static,and communications may be less sub-ject to interruptions.

SOLAR ACTIVITIESThe sun is the star about which the earthand other planets of our solar systemrevolve. It is the only star the surface ofwhich we can see. All other stars, eventhrough the best telescope, appear onlyas point sources of light. Like most otherstars, the sun is a hot, glowing sphere ofvirtually pure hydrogen gas held


Shortwave World

together by gravitational attraction. Thelight we see is created deep in the solarinterior by thermonuclear reactions inwhich hydrogen atoms are fused to formhelium atoms. After trickling through thesun, the radiation escapes from thePHOTOSPHERE, a very thin layer at thesurface.

Above the photosphere lies the outersolar atmosphere - the CORONA -which extends for many solar radii andultimately blends into the interplanetarygas. Because the coronal gas is verythin, it shines only faintly. Ordinarily hid-den from view by the brightness of thedaytime sky, the corona becomes visibleduring a total solar eclipse.

The gas density is highest at the sun'scenter, and steadily lessens towad thesurface. The temperature, on the otherhand, falls from about 13,000,000°K(°K =°C + 273) at the center to about4,000° K at the top of the photosphereand then rises again until it reaches1,000,000°K in the corona. The reasonfor the high temperature of the corona isas yet incompletely understood.

The CHROMOSPHERE is a transi-tional region between the photosphereand the corona. It owes its name to thebright red light that it emits during a totalsolar eclipse.

On the average the sun undergoes aneleven -year cycle of activity. (The cyclehas ranged from 7.3 to 17.1 years). Dur-ing this period, the number of sunspots(dark patches on the photosphere),flares (sudden brightenings of the chro-mosphere), and prominences (cool,dense clouds of hydrogen suspended inthe corona) varies in a remarkably regu-lar fashion.

A SUNSPOT is fundamentally aregion in the photosphere where astrong localized magnetic field emergesfrom the interior of the sun. The pres-ence of the field inhibits the upward con-vective transport of energy in the layerjust below the photosphere. Hence thegas of a sunspot is some hundreds ofdegrees cooler than its field -free sur-roundings, and appears darker. Indi-vidual spots usually possess a dark core(the UMBRA) surrounded by a some-what brighter PENUMBRA. On the aver-age, the temperature in these tworegions may lie 1,500° K and 400° K,respectively, below the normal photo-spheric temperature. A spot first appearsas a dark "pore" only 1000 miles or soacross. Most pores disappear in lessthan a day, but a spot may persist forweeks and grow to a diameter of 19,000miles. Sunspots move with the rotationof that part of the sun's surface uponwhich they appear.

60

Sunspots normally associate ingroups of two to fifty. The group mayexhibit a predominantly bipolar mag-netic field, with spots of opposite mag-netic polarity clustering at opposite endsof the group. Multipolar groups are alsoquite common.

The total number of sunspots variesperiodically in an eleven -year cycle. Atthe beginning of a cycle, new spots format high solar latitudes. As the cycle pro-gresses and the total number of spotsincreases, spots form at progressivelylower latitudes. A cycle ends with a fewspots forming and breaking up at lowsolar latitudes. During a cycle most ofthe "leading" (westward) spots of bipolargroups in the northern solar hemispherepossess the same magnetic polarity.Leading spots in the southern hemis-phere show the opposite polarity. In thenext cycle the polarities of leading spotsare reversed.

The chromosphere overlying a sun-spot group may brighten suddenly andspew off gas at high speed. This event iscalled a FLARE, and it is one of the mostcomplicated and least understood phe-nomena on the sun. Most flares are in-visible in white light and can be seenonly with special equipment and tech-niques. During the onset of a flare, theenergy radiated may increase tenfoldwithin minutes, then return to its originallevel within an hour.

Flares tend to break out near sunspotgroups of complex magnetic structure,especially near groups in which newsmall spots are growing rapidly. Such agroup may display several flares in a day.Small flares occur with the greatest fre-quency, large flares are rarer. The larg-est flares attain an area of 0.1 percent ofthe solar disc.

Flares also emit a complicated radiospectrum. During the early phases of aflare, fast "bursts" of radio -frequencyradiation are often detected. The fre-quency of the burst falls from 600 to 100megahertz in a few seconds, which sug-gests the propagation of a disturbancethrough the corona at speeds up to atenth the speed of light. Following a vol-ley of fast bursts, a slow burst may occur.The frequency drop takes place within afew minutes.

In both types of burst, the drop in fre-quency can be interpreted as the effectof a rising disturbance. At every pointalong its path this generates radio noiseof all frequencies, but only frequenciesabove a "critical" value (which is deter-mined by the local electron density) canescape from the corona. As the distur-bance moves outward through thecorona it encounters a lower elec-

tron density (i.e. critical frequency), andthus lower and lower frequencies canbe emitted.

Much thanks this month go to BillButuk of Thunder Bay for his researchinto the solar conditions which have somuch to do with the way we are able tohear radio programming from the otherside of the world.

As I'm typing up this article I'm listen-ing to some beautiful Island music fromTahiti (15170 Kilohertz at 0330 GMT).This is one of my favorite stations in thelate evening hours. The language is Tahi-tian but the music sounds good in anylanguage.

SHORTWAVE MAILBAG, P.O. Box 142,Thunder Bay, Ontario, P7C 4V5.

H. Sparreboom of Tofield, Albertawrites: "I have been reading variousmagazines on this hobby, but it wasn'tuntil last month that I picked up "Elec-tronics Today". I find the equipmentreview of shortwave radiOs more useful,since the prices are more accurate. Per-sonally I would like to see more technicaldata included such as sensitivity andselectivity and possibly some compari-sons of the various receivers.

"At the present I am experimentingwith an 8 band multiple dipole antenna. Iuse rotor cable with each wire cut to thedesired length.

"Numerous countries broadcast fromvarious locations such as Radio Neder-land from Holland, Bonaire and Mada-gascar. Does this count as threecountries heard or do you just countHolland for all transmissions?"

- In a few months I will have a summaryof radio receivers that have beenreviewed. This will be in the form of achart with technical specs and compari-sons may be made. - Your idea of usingrotor cable for a multiple dipole soundsvery good. - If you hear Radio Neder-land from all three locations, this wouldcount as three countries heard. Thankyou very much for your letter.

RECEIVER REVIEWLast month I had a review of RadioShack's latest receiver, the DX -300. Thismonth we will look at other shortwavereceivers from Radio Shack. RealisticDX -40 - This is a four band portablewhich tunes AM and FM and 2 shortwavebands covering 4 to 12 MHz and 12 to 22MHz. Features of the DX -40 are slidingvolume and tone controls, 31/2" speaker,SW fine tuning, pushbutton band selec-tors. The receiver operates on house cur-rent orfour'C' cells. The set measures 305


SWL Via Ionosphere

mm wide, 180 mm high and 93 mm deep.The Canadian price is $64.95.

Realistic DX -60 - Another portable sim-ilar in size to the DX -40 but with threeshortwave bands covering 3 to 7 MHz,and 18 to 26 MHz. The AM and FM bandsare also included as well as a CB bandcovering all 40 channels. The DX -60 has afour inch speaker, built in AFC, 30" tele-scoping antenna for FM/CB/SWantenna, built in AM antenna. It also oper-ates on housecurrent orfour'C' cells. TheCanadian price of the DX -60 is $89.95.

Patrolman CB -8 - An eight band porta-ble featuring just the Shortwave band of 6to 18 MHz as well as AM, FM, CB, CHF-Hi,VHF -Lo, UHF and VHF -Air. Anothershortwave band would be an improve-ment. The set has dual antennas, fine

DX -40

DX -60

CB -8

Path of RadioWaves in theIonosphere

tuning, adjustable squelch, tone control.The CB -8 operates on AC or six 'C' cellsand costs $149.95.

Realistic DX -160 - This is one of themore popular communications receiverespecially among new SWLs/DXersbecause of its low cost. It is a very goodreceiver for its price. The main disadvan-tage is that the tuning is not the directreadout type as is used on the moreexpensive sets but the slide rule typemaking it difficult to know the exact fre-quency to which you are tuned. This is afive band set - 150 to 400 kHz Longwave,535 to 1600 medium wave, 1.5 to 4.5 MHzshortwave, 4.5 to 13 MHz shortwave, and13 to 30 MHz shortwave (which alsoincludes CB channels 1-40). A productdetector and variable BFO bring SSB andCW reception. Eleven front panel con -

67/

Mit

trols including electrical bandspread tun-ing and calibrated logging scale. Alsofeatured are FETs in all critical stages,Zener stabilization, noise limiting in IFand audio stages and illuminated 'S'meter. A separate speaker is included.The DX -160 operates from 120 V AC or 12V DC negative ground. Dimensions are165 mm high, 362 mm wide and 235 mmdeep. The Canadian price is $229.95.

Now that summer's here it would be agood time to think about buying a porta-ble shortwave receiver and get out in thesun and enjoy the thrills of shortwaveradio. And don't forget that if you arevacationing outside of Canada you cankeep up to date on Canadian news bylistening to Radio Canada Internationalon shortwave.

Until next month 73 and good listening.

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DX 160

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Fro-0/ 0j"r<e0 .e4,,,, 0,..,..N; ,'IN 4.0";,is';'>_ ii...;t4.,,0,:c.>,,,6: ,The ETA isn't the estimated time of anything, except that we estimate that the "vs ">6.0, .,,, 4.56. .time has arrived for more than a few Canadian technicians to be interested in th.s % '''oe'j aU. S. based organization. Dick Cartwright checks them out. % e''' ee

HI!After being requested by the Editor -inChief to do an article or series of articleson associations in our Province and/orCanada, I received a call from the maga-zine informing me that an association,ETA -I, was now operative in Canada.Orders: Oheck it out.

Very little research was required as Ihad through the office received anumber of communications making itobvious that there had been some inter-nal strife in the American association,the International Society of CertifiedElectronic Technicians (ISCET). Anumber of directors of this association(ISCET) had apparently become dissat-isfied with progress being made, or lackof it, and decided to form a new associa-tion, so Electronic Technicians Associa-tion International, Inc. (ETA -I) wasformed.

ETA INTERNATIONALThis news release from ETA Interna-tional dated Nov. 10/78 was receivedNov. 21, at my office for immediaterelease. (At that time controversy, con-frontations, etc. within the various Amer-ican associations seemed of littleinterest to my Canadian readers, and Idid not report on them; however subse-quent developments make it necessaryfor Electronics Today to do so.)

ETA INTERNATIONALformed as new electronicstechnicians association"Today a group of interested techniciansmet in Indianapolis to form a new tradeassociation: The ELECTRONICSTECHNICIANS ASSOCIATION, Inter-national, Inc. The association will becomposed of individual member techni-cians, rather than being a business

league such as is typical of the otherpresent industry trade associations."

Here follows a list of the directors ofthis association, a number of whom wereprevious directors of ISCET:Chairman: Jesse B. Leach, Linthicum,Md.Vice -Chairman: D. C. Larson, Houston,

Texas.Secretary: Leon F. Howland, Jr.,

Indianapolis, In.Treasurer: Walter Cooke, Hampton, Va.EEA Division Chairman: Ron Crow,

Ames. la.The objectives of ETA are to provide aprofessional trade association for allelectronics technicians; to expand andimprove the present industry Certifica-tion programs for technicians; to estab-lish continuing technical educationalopportunities; to set training and com-petency standards; to collect, preserve,and distribute valuable technical infor-mation and to promote the interests of allelectronics technicians.

A new educational division of ETA -Iwas included in the association struc-ture. Its name is to be: ELECTRONICSEDUCATORS ASSOCIATION. RonCrow, a previous director of ISCET waselected to head the division. Mr. Crow isalso presently division head of the Elec-tronics and Technical Education Exten-sion at Iowa State University andsupervisor of the Engineering ResearchInstitute Electronics Shop, at ISU.Edward T. Carroll, CET, an instructor ofElectronics Technology at the IndianaVocational Technical Institute in India-napolis was elected as Secretary/Trea-surer of the division.

Returning to the apparent controversydeveloping within the ranks of ISCET,Chairman Leach stated that "The contin-uing and deepening rift within NESDA

has forced technicians to seek otheropportunities for a representative asso-ciation. In ETA we expect to carry onprograms such as Certification, Serv-iceability and educational seminars sim-ilar to those presently administered byISCET. We also are expanding the mem-bership potential to the more than250,000 technicians in the United States.Hopefully, by establishing the governingbody as an elected Board of Directorsrather than regional allied groups, wewill have eliminated the seeds of dissen-sion which have dampened past serviceassociation efforts."

IN CANADA YOU SAY?Ncw as previously mentioned, the fore-going events and information seemed tome at that time to be of little interest orimportance to Canadian readers, until afurther nudge from our editorial staffpushed me out of my winter hibernationand it became apparent that yet anotherassociation, ETA -C (Electronic Techni-cians Association - Canada) had sur-faced here in Ontario (Canada). A seriesof phone calls and a belated research ofmy files quickly brought home to me thefact that our first international technicalassociation was emerging.

A letter was received in my office fromMr. Bill Patullo who is the president ofthe Canadian branch of ETA -C. In thisletter Bill stated that although at the timeof writing, membership was relativelyinsignificant, he was confident that pub-licity, word of mouth, etc. would spreadthe word to the thousands of techniciansacross the country that here was anassociation devoting itself to the indi-vidual electronic technician.

Mr. Patullo sent me copies 01 lettersfrom Mr. Dick Glass, CET, the presidentof ETA -I, and Mr. Ron Crow, CET, Direc-


Service News NOTE: As we go to press we hear that the 3 day meeting mentionedin this article is to be held on August 3-4-5.

tor of Certification, Educational DivisionChairman. With these letters it becameobvious that this association, unlikemany of its predecessors, was not start-ing off with just high-sounding idealsand aspirations, but was already a thor-oughly organized and directed associa-tion, and a quick perusal of the board ofdirectors explains a great deal, as herewas a considerable part of the previousboard of ISCET.

A further news release was received inthe latter part of April from ETA, asfollows:

"TECHNICIANS' ASSOCIATIONTO MEET IN CANADA""Annual Convention to be ETA's First.According to Dick Glass, CET, Presi-dent of ETA -I, the new internationalassociation of electronics technicianswill hold an annual convention thissummer in Kitchener, Ontario, Canada.

"Meeting in Yorktown, Virginia, April14th, ETA's officers made the decision toconduct an annual convention despitethe group's short existence of only sixmonths. Chairman Jesse B. Leach, CET,said: 'It may appear to be a bit too soonfor ETA to hold an annual member meet-ing, but strong support and memberinterest dictates that ETA 'get on with theprogram', and exert its efforts towardsimproving the profession for electronicstechnicians. An international conventionwill help the association to jell and toconvince those who have been sitting onthe sidelines to know that ETA is here tostay.'

"Exact location of the convention will

be announced later as will the specificdates for the planned 3 -day confab. Thetentative dates are for July 27-20inclusive.

"In addition to the election of officersfor ETA -I and the three divisions: ETA;ETA -Canada; and CTD, the CertifiedTechnicians Division, the convention willconcentrate on training ideas includinglecture -seminars; training for electron-ics instructors; and methods -training forcertification administrators and localETA chapter leaders.

"Technicians interested in attendingthe Canadian convention should call317-241-7783 or write to ETA -I, 7046Doris Dr., Indianapolis, Indiana 46224."

Canadian technicians requiringfurther information contact Mr. BillPatullo, 10 Windywood Crt., Kitchener,Ont. N2N 1L5.

COMMENTSAssociations! I am suddenly up to myneck in them and I have not even dis-cussed our original tried and true RETA,of which I am a past president. For nearly25 years the surface of the electronicpond was rippled only occasionally byassociations or ideas re associations,and basically except for the odd furoreinstigated infrequently by newspaperarticles we, the domestic electronicindustry, continued on in a reasonablyplacid fashion, but storms like all stormsquickly subsided and our local techni-cians carried on much as before with an"I'm all right, Jack" attitude.

But then with the advent of MTTSA,which had some political clout, some

technicians began to change their atti-tude regarding the need for or lack of aprofessional technicians association.CEASA, the subject of my previous arti-cle, appears to be doing a great job, andas previously stated I can see no earthlyreason why our Ontario associationshould not, in one way or another, affil-iate themselves with this rapidly growingorganization. Now we have ETA -C (Elec-tronic Technicians Association - Can-ada) who are already firmly establishedin the U.S.A., expanding into Canada,and the first chapter, based in Kitchener,is apparently already fully operational.They, like our old friends of RETA, aredirecting their main thrust to the individ-ual technician as opposed to OETA'sattention to the business owners.

Conversations with the president ofOETA and a member of the board of theToronto chapter (MTTSA) produced nointeresting response, though Mr. Steen-huysen (President, OETA) did at my sug-gestion arrange to send a representativeof his group to a meeting held by ETA -Canada in Waterloo on May 1st. As amatter of interest, though it was at mysuggestion that he sent a representativeto this meeting, he did not think it impor-tant enough to comment on the pro-ceedings. It is fairly obvious that OETAdo not feel that ETA -I (Canada as well)pose any threat to their associationstructure, but my opinion, after talking toa number of technicians, is that theyshould maybe look very closely at thisnew competition.

All the best.Richard H. Cartwright

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_-°\1[K1 QRM

Hams are essential to the preservation of society as we know it! Bill Johnson,VE3APZ tells how.

AS amateur radio operators , we some-times feel it is our duty to volunteer ourservices to government agencies for pub-lic service communications. Those of uswho have phoned our local police andother agencies to announce our presenceand readiness know well the general att-itude of indifference displayed towardsus. Several events have occurred in thelast few years in the Toronto area, how-ever, that seem to indicate that thetimes are changing. In September 1976the Toronto ARES group (AmateurRadio Emergency Service) and TFM(Toronto FM Society) were involved ina multi -agency simulated aircraft crashat Toronto International Airport. Dur-ing the exercise, amateurs from theToronto area passed hundreds of health -and -welfare and medical messages be-tween the airport and several Torontohospitals.

During the months following the ex-ercise, there was much consultation be-tween the Ontario Hospital Associationand local amateurs with a view to estab-lishing a local amateur radio networkbetween the Toronto hospitals, with atleast the antennas being paid for by thehospitals. The plan has not, to thisdate, materialised, probably because ofcutbacks in hospital spending. The localEmergency Co-ordinator is, however,hopeful.

Various police departments are learn-ing more and more about amateurradio's capabilities, as is evidenced bytheir more ready acceptance of emerg-ency calls via autopatch without a lotof questioning.

It is, therefore, somewhat not sur-prising to hear that the Canadian CoastGuard, in forming a volunteer reserve,has announced that it will be recruitingamateurs to provide communications.Five units of the Canadian MarineRescue Auxiliary, Inc., are being formedby the Department of Transport. Theseunits will each sign written agreements

with the Ministry to provide emergencyand routine assistance to the regularcoast guard units. In return, the auxili-ary units will receive specialised trainingin search and rescue, boating safety, andPR work, as well as being provided withinsurance for their equipment while us -PR work, as well as being provided withinsurance for their equipment while us-ing it for official coastguard duties.

All vessels used in the auxiliary willbe owned either by individuals or cor-porations who are public service -mindedenough to volunteer their facilities.Since few pleasure craft use the veryexpensive VHF marine radios, Amateurswill be enlisted to use portable andmobile equipment as a liaison betweenland and marine stations.

For those of you out there who arealready 'chomping at the bit', be

patient. At the present time, the fiveauxiliary units (West Coast, CentralCanada, Laurentian, Maritime, andNewfoundland) are just forming andlooking for people with boats. Amateuroperators may offer their facilities aswell, but these applications will be heldon file until such time as the organisat-ion of the boaters is complete. Don'tlet this discourage you though, get yourapplications in soon, so they can get anidea of how many we are and what wecan do. You can get application formsby calling the Canadian Coast Guard inToronto, Vancouver, Quebec, St. Johns,or Dartmouth.

LESSON - OF - THE - MONTH

With the increased use of VHF andUHF equipment, amateurs are subject-ing themselves to more and more RFenergy by the day. We have alwaysbeen involved with high -power RF, butwe don't usually climb our antennatower while it is being used to transmit.

Since VHF/UHF lends itself to easymobile and portable operation, espec-

II

ially with the numerous repeaters nowin operation in all but the most remoteparts of the country, it is natural fora lot of amateurs to own and operatelow -power portable equipment of thehand-held variety.

Some more recent models of thistype of radio have, as an optional extra,a remote microphone that plugs into theside of the unit, so that the radio maybe held above the head, on the bodyand the radio still used. While the ad-vent of these accessories is due mostlyto their extra convenience, there is a

very good reason why the amateur buy-ing a portable should consider the extracost. When these radios are being usedto transmit, they are held so that themicrophone is directly in front of theuser's mouth. This places the antennastrategically in front of the victim'sforehead, where most damage can bedone to the living tissues of the humanbody. Recent studies of 450 MHz equi-pment have shown a decided heatingeffect in the skull. While this is only ofminor proportions, we all know of thepositively carcinogenic nature of micro-wave radiation. 450 MHz is gettingpretty close to the microwave region, soit is better to be safe than sorry. Theamount of energy radiated is directlyproportional to frequency and power,so the higher up in frequency you go,the less power it takes to do the dam-age.

I don't want to be a scaremonger, butyou should consider a remote speaker -mike if you are going to use a VHF/UHF portable radio whose outputpower is more than a watt or so. Thisis especially important to those peoplethat insist on ragchewing on repeaters.And you thought that timing out therepeater was the only danger

QRM LETTERS

In the March issue of ElectronicsToday... in QRM ... it was suggested by


QRMJ. Riddell that you 'buy a copy of the'Radio Amateur's Licensing Hand-book'. In February 1979 ALHPublishing Co. informed me 'Sorry, all10 editions sold out. Probably no moreunless we can find somebody capable oftaking over, as the author has retired.'

Anyone out there capable of fillingin the vacuum?

Yours Truly, F.P., Thompson, Man.

(It was actually Bill Johnson who wrotethat. J. Riddell's name was at the end ofa letter, not the whole article. Watchthis column for further developments)

Dear ORM letters,You asked for it - you got it.In response to your February 1979

ETI, this is to let you know that thereare some amateurs out there in Ontariothat do read ORM.

The magazine is a good one, coveringa range of interests in the electronicshobby. I am not much of a builder butam glad to see a 'Canadian' magazinewith some construction projects. Per-haps in the future there will be moreamateur -related projects. i.e. VSWRbridges, speech processors, scope adapt-ors for modulation indicators, andRTTY work,etc.

I would like to see the personal ob-servation context of QRM continue. I

would also like to see QRM expanded to

more than one page and cover theCanadian amateur activities as well asDX news, Hamfests and regulationchanges and proposals.

The magazine as a whole is good, butin keeping with the 'state of the art'let's not forget the basics. ICs are notthe living end. There are still a lot oftransistor and tube circuits that manypeople are interested in because they donot represent a .'black box' approach.The 741 op -amp article is OK, but howdoes the 741 work itself?

Back to the subject at hand. Duringthis calendar year the number ofCanadian amateurs should reach 10,000.I have purchased parts from your ad-vertisers because I heard of themthrough ETI. I am sure other hams havedone the same. So, we all profit in theend.

To sum up; a good magazine with agood column (QRM). As long as QRMis in there, so too shall I. Keep up thegood work and let's get QRM expanded.

Congratulations Bill on Digital Ticket

73,

Larry Van Wart, VE3I VO

(You can see the original in my hallwayif you don't believe it. Framed.)

With that, all I can say is 73.See you next month.

Bill, VE3APZ

MOTOROLAMOTOROLA COMMUNICATIONS

TWO WAY RADIOFIELD SERVICE

CHALLENGING: Career in servicing mobile communication equipment.Chance to work on a total line of products including mobile, base, repeater,and, special systems.

REQUIREMENTS: Amateur radio license or three years experience in thecommunications field, plus technical school certificate. Must be self starterand possess a valid drivers license.

EXCELLENT: Employee benefits including prbfit sharing and advancementin the company based on individual merit programme.

PLEASE SEND RESUME TO:

EMPLOYMENT SUPERVISORMOTOROLA CANADA LTD.3125 STEELES AVE. EAST.WILLOWDALE, ONTARIO

M2H 2H6ATTENTION: Toronto Service Manager

66

411,JanaELECTRONICS LTD.

Distributors stockingJana Projects:

A-1 ElectronicsISLINGTON, ONTARIO

Arkon ElectronicsTORONTO. ONTARIO

Atwater ElectronicsMISSISSAUGA, ONTARIO

Brant Electronic SupplyBRANTFORD, ONTARIO

Carsall IndustriesSAULT STE MARIE, ONTARIO

Robert J Buckland CoLONDON. ONTARIO

Dominion Radio LtdTORONTO. ONTARIO

General Electronics CoWILLOWDALE. ONTARIO

Gladstone ElectronicsTORONTO, ONTARIO

Heath CompanyMISSISSAUGA. ONTARIO

Jerry's T VSARNIA. ONTARIO

Kesco Electric Supply LtdPETERBOROUGH. ONTARIO

Kingston Electronic Supply LtdKINGSTON, ONTARIO

Lighthouse ElectronicsWINDSOR. ONTARIO

Lamp Land LtdPETERBOROUGH. ONTARIO

M I Supply Co LtdBELLEVILLE, ONTARIO

Neutron Electronics LtdGUELPH, ONTARIO

Niagara T VNIAGARA FALLS. ONTARIO

Northwestern Electronics SupplyOWEN SOUND, ONTARIO

Provincial Electronics DistributorsLONDON. ONTARIO

Radio Trades Supply LtdTORONTO. ONTARIO

Sonic NorthernSUDBURY, ONTARIO

Teltronics LtdSCARBOROUGH ONTARIO

D R. Walling Co LtdLINDSAY. ONTARIO

Waterloo Electronic SupplyWATERLOO ONTARIO

Western Radio Supply CoHAMILTON ONTARIO

Westown ElectronicsTORONTO. ONTARIO

If you cannot find JanaProjects in your area,contact Doug Mann,Jana Electronics Limited,P.O. Box 489, Winnipeg,Manitoba R3C 2B3.

30 -waif soldering iron:It's so good, yo 'II beproud youmade it.

Where do you start learning electronics? Janalets you start right at the beginning by buildingyour most essential tool.

Getting a superior soldering iron at Jana'slow kit price is only part of the advantage. Know-ing how it works is important too.

No doubt you will later heat your iron up often.You will use it to solder transistors, diodes, chipsand other elements into increasingly sophisticatedprojects. In time your solderingiron's efficiency will wear downa bit, but you will know how torestore it to peak performancebecause you built it.

Like all Jana kits,you get everythingyou need. Janaeven includes twosmall screw driversand tweezers youcan use for pickingup small parts. (They also

Jana Electronic Projects are available through Cam Gard Supplyand other distributors across Canada (partial list on facing page).

tools yourself!

make a great heat sink.) Jana's step -by -s ep in-structions include large, easy -to -follow illustrations.

111111.11MAIMISMI

CAM GARD SUPPLYaDllllllllllllllll VI llllll 111111411111

Vancouver Kamloops Calgary Edmonton Red Deer ReginaSaskatoon Winnipeg Halifax Fredericton Moncton

1. Automatic HeadlightReminder

2. Battery OperatedFluorescent Light

3. Bug Shoo4. Code Oscillator5. Crystal Radio7. Curiosity Box II8. Daily Lighter9. Decision Maker

10. Fish Caller11. Hi Power 12V DC Flasher12. Photo Electric Night Light13. 6V Power Supply14. 9V Power Supply15: 0-20V Power Supply16. Single Channel Color Organ

Start by building a Janasoldering iron. Then, beforemoving on to building yourfirst computer, try a few moreuseful, entertaining Jana kits.Every one can increase yourelectronic expertise andunderstanding.

Jana kits for many useful andentertaining purposes 17.

18.19.20.21.22.23.24.25.26.27.28.29.31.32.33.34,

Electronic SirenShimmer Strobe LightTone Generator5 Transistor 1 Watt AmplifierTube Continuity CheckerXenon Strobe3 Channel Color OrganLoudmouth SirenRoulette WheelElectronic Skeet GameElectronic DiceSuper RouletteFM Mini BroadcasterShoot OutRoad RunnerLove -O -Meter30 -Watt Soldering Iron Kit

,dio Wattmeter

Industrial1777 Ellice Ave., W nnipeg, Man. R3H OW5 Phone: (204) 786.3133

Electronicsand CowsWhen farmers first found cows milked better with FM radio, the electronic age forfarms began! Now, they've got them on TV! Jim Essex explains.

WHAT'S THE PURPOSE of cows onTV? How'd it get started and how does itwork?

The use of TV for selling cattle is anew idea. In fact, the first TV auction inHanover, Ontario, was the first inCanada in which feeder cattle wereactually sold via closed-circuit TV!

When the idea of this unique methodof selling cattle was first mentioned lastyear, sceptics abounded. When firsttried last fall, the only sign that thiscattle auction was very different wasseen in the parking lot. The usual largetrucks were there, of course; but whatwas surprising was the preponderanceof ordinary cars and light pickup trucks- a clear sign of acceptance by thesmall, independant farmers who don'thave big trucks. The usual enclosure,inside the barn for parading cattle, wasmissing! In its place, was a huge"projection -type" TV screen, like thetype widely used in hotel bars. But whatwas even more surprising was the factthat the cattle to be shown were absent;instead, what the farmers were going tosee was all contained in a videocassettesmall enough to fit inside a lady's purse!

How did all this come about? Andhow can so much be processed into aseemingly insignificant video cart?And, could electronic pictures of cattletake the plate of the real thing?

II all bega when six farmers from thebeef -rich Bruce County area realizedthey were losing money under the oldmethod of auctioning cattle. Thehazards involved were endless. Manytimes, they watched helpless while theircattle were shipped south to the hugestockyards in Toronto only to havehopes dashed when the offered pricedidn't meet their expectations. To shipcattle all the way back was too costly -and cattle kept in close quarters toolong lost weight. In addition, diseasefrom one is easily spread to others andthey faced the hazard of bringingcommunicable disease back to theirown farms. It was then they came up

with the idea of "showing" theircattle -without them ever leaving the barn! Theenthusiasm of the group was onlymatched by Ginty Jocius, manager ofthe Ontario Beef Exchange. Togetherthey formed "0 B E X" (Ontario BeefExchange) and set to work.

Most of the cattle are winter calvesbrought down the previous fall andfattened in Bruce, Huron andsurrounding counties. Here, they aremaintained through winterand grassedout to stocker or short -keep weight fcrfall sale. These cattle have a reputationfor pretty high quality, so what theydeveloped had to work.

They found help from Hill's TV, whoprovided the Projection screen andaccompanying "Advent colorprojector." (see Electronics Today May'77). This gave a working image ofsufficient brightness and detail tomatch the Sony electronic camera

model 1610 used with a 3800 recorder.Additional viewing would be providedby strategically placed 26" colormonitors. Jim Sutherland of Lucknow,Ontario was employed to put it alltogether. (He now works full-timedoing nothing but camera -takes oncattle). The 2" tape used mostly inBroadcasting was too costly, so theysettled on 3/4" tape, - and were away.Luckily, nearby CKNX Wingham,Ontario can handle three-quarters, andJim found them immensely helpful inediting. As transpired, this proved to bealmost a necessity, for "shooting" is arandom thing as it can be difficultgetting the cattle to do what you want.The audio was added later for thisreason, with "lots" and "numbers"describing each as the cattle paradepast the screen. This resembles theparades which take place in thecustomary ring prior to an auction sale.

Fig. 1 Jim Sutherland takes video-tape movies on the farm.


Electronics and Cows

COW PARADEWhen they had their first production

test runs complete, all were satisfieddetail "was as good as life". They wereready.

The enthusiasm of the group wasonly matched by the enthusiasm ofpreparation. Problems such as how toget the cattle to move when Sutherlandarrived at each farm for pictures wereresolved with a measure of "homegrown" practicality! At a signal fromSutherland, perched on the back of hisvideo van (see picture fig. 1), the farmersimply drove a truck with a bale or two ofhay on the back into the nearest field,and the cows followed, chasing the haywhile Jim took pictures. How theylooked "on the screen" can be seenfrom Fig. 2.

The "Video Sale" was held in a regularsales barn - chosen as against anauditorium - the thinking here beingthat farmers feel moreat home in a barn!The sale was conducted just like a liveauction, with the usual display ringsubstituted by the huge screen. Theauctioneers, themselves, were placedjust to one side and a little to the left ofthis screen where bids were received,again, in the usual manner, as with aproper auction. (Fig. 3). For those whowanted to go for coffee breaks, - yetnot lose out on the proceedings, -smaller 24" monitors were placedthroughout - another innovationwhich sold the system to buyers.

AMAZINGAfter it was ALL over, buyers

expressed amazement at how well thecattle were portrayed. The over -flowcrowd of 700 plus gained as much, if notmore insight into what they werebuying, as the TV display adequatelytold them about numbers,' weight,delivery date and, of course, the terms.Most farmers had their money within 48hours of the auction. But what was thereal clincher was the fact sellers at lasthad the option of refusing the first bid,- since his cattle were still at home onhis farm! Ernest Acker, one of the sixowner -operators of OBEX, said he andhis partners are "exceedingly happywith the reception" given by beefproducers across Ontario.

STARTLING STATSThe statistics are even more startling:

To market cattle the old way, it costssomewhere in the vicinity of $21.00,including trucking, brokerage fees,insurance etc. The TV was runs only $9.to $10! And that's for each head Evenlocal yards may run upwards of $15.00or more, so the saving is obvious.Disease, mentioned earlier, and things

F/G.2 Advent reproduction of cattle as seen on "Advent" Screen Hanover,Ontario.

like weght loss - also costing thefarmers dollars, - are now non-existent! A total of 2,897 feeder steers &heifers at an average weight of 900pounds were sold in about three hoursat Hanover! Sutherland reports thatwith practice, he can now video-tape1000 head in an average week, - with ahigh of 1800 attained. And in a 1000head lot, it is not uncommon to sell 800of them right off, with no truckinginvolved and absolutely no diseasecarried back to farms for those whicharen't sold. If the buyer's a dealer, all thebetter; they're fresh for re -sale.

A fringe benefit from all this has beenthe speed with which a "show" can berun off. Auctioneers don't have liveanimals to deal with, which can beornery at times, and the hassle gettingthem in and out of the ring can be timeconsuming. You just need smarttechnicians, who if treated right, aremuch easier to handle! This first sale inCanada took a mere three hours, and allfarmers participating were guaranteedpayment, most under 48 hours.

The result of this large scale auctionhas successfully inaugurated smallerweekly auctions right in Toronto. Using24" monitors, representatives from themajor packing houses bid the cattle tobe used for slaughter now without everleaving the office.

REPERCUSSIONSThe forward step taken at Hanover

will have repercussions throughout thebeef industry. It's now conceivable thatwestern cattle could be filmed in far-offwestern pastures and auctioned off toOntario feed -lot owners without thecattle ever having moved off their homepastures. In one fell -swoop, the

intermediate hassle of shipping andhaving to move through timeconsuming auction rings is thuseliminated, thanks to electronics. Highprices and reduced disease can makeTV auctioneering even more attractivewith the anticipation of new marketssoon to be within reach of every farmer.A seller can offer a buyer someadditional advantages as well. Mostsellers at Hanover allowed a "cutback";that is,. the buyer could sort out a certainnumber of animals on each lot that hedidn't have to buy. This eliminated thechance of getting stuck with a few poorcattle, - increasing selective buying.

This first TV auction may be theherald of greater things to come for thecattle farmer - far exceeding that firstexperiment of playing radios to cowswhich made Carnation's "ContentedCow" slogan a reality.

Fig. 3 Auctioneers "calling the tune "atHanover Cattle Auction.


The

FunElect-ronics

,ccccLC,

117_3 CI

f

In this laboratory, we'retrying to solve the toughestproblem the watch industryhas ever had -namely howto put mickey mouse's face

7 a digital watch.

NOW YOU CAN

BUY A BATTERY & CHARGE I r!

The sign means that wetake credit cards not, thatwe sell dead batteries, wiseguy.

6e2Ce-R,

111111,.

I need a zener diode-The diodes I haveat home are'nt zene enough.

I spent $75 on an electronic combination lock that has over9,000,000 possible combinations & virtually impossibleto open if you don't know the correct sequence of digits.

Last night a burglar kicked the doordown & robbed the house.

l

c

Now that- I've sold

my CB& bought

a short-wave radio

don't haveto listen to

noise andstatic from

all overthe city...

I can listento international noise and

static from all over the world.


'N

ETI's new classified advertising section allows you to reach30,000 readers nation-wide. For as little as $15 (there's a 20word minimum) you can promote your business from coastto coast.

WHAT DO YOU DO?Send us your typewritten or clearly printed words, your per-manent address and telephone number, and your money (nocash please). Make your cheque or money order payable to'ETI Magazine'. We're at Unit 6, 25 'Overlea Blvd, Toronto,Ontario, M4H1B1.There's no charge for including your postal (or zip) code. V youwant to test reader reaction you can include 'Dept. ETI' aspart of your address (free of charge).

WHAT DO WE DO?We typeset your words (and put the first word and your com-pany name in bold capital letters).If we get your message by the 14th of the month, it will appearin ETI 1Y2 months later. For example, if we receive it by Nov-ember 14th, you (and thousands more) will see it in the Jan-uary issue.

CLASSIFIED

NEW STORE! for the Hobbyist. HamAudio, CB'r. Special: Video Cameraand Monitor $349.95. Ont res. add 7%sales tax. GENERAL ELECTRONICS, 5511Yonge St., Willowdale, Ont. 221-6174.

COMPONENTS; Digital and Analog IC's,Transistors, Diodes, Zeners, Resistors, LED's,Displays. Send for Free Price List.ELECTRONICS LONDON, Dept ETI, Box7096, London, Ontario. N5 Y 4J9.

YOU need it? Chances are we sell it! Send usyour parts list for free price quotations. Don'tforget our fist and flyers come out regularly,Don't miss out! BRYAN ELECTRONICS,P.O. 2068, Bramalea, Ontario. L6T 3S3.

J&J ELECTRONICS LTD., P.O. Box 1437 E,Winnipeg, Manitoba R3C 2Z4. Surplus Semi-conductor Specialists. Do you get our bargainflyer? Send $1.00 to receive thecurrent literature and specials and to beplaced on the mailing list for future publica-tions.

$1.00 Unusual Canadian and American partsand surplus catalogs. Hundreds of bargains.ETCO, Dept 087, 183G Hymus, Point:. Claire,Que.

SPECTRUM ELECTRONICS * Quality pcbs* 2 wks Del. * 50c P&P * Ont res. add 7%PST * 38 Audubon St. S., Hamilton, Ontario,L81 1J7 * ETI 551: $5.15; 136: $1.65;553:$6.70; 812: $4.10, kit: $5.35; 490 $3.90;592: $14.80; 593: $5.45, kit: $26.25; 062:$2.65; 243: $2.00; 555: $5.15; 650A: $8.15;650B: $3.15; 650C: $1.95; 072: $2.50.

AUDIO compressor parts kit $22.78: Wheelof Fortune parts kit $17.50; both includePCB. We stock boards from Feb. 1977 tocurrent issue, write for full list to:- B&RELECTRONICS, Box 6326F, Hamilton, Ont.L9C 6L9.

WSI RADIO - SWL Radios - Ham radios -

18 Sheldon Avenue North, Kitchener, OntarioN2H 3M2. Telephone (519) 579-0536. Writefor giant catalog, free of course!! (VE3EHC)


I

ISSUEDATE

Space restrictions did not allow us to print the pcb patter forthe Light Show Sequencer, ETI 593 last month: here it is.

ARTICLE

Apr 78 Computer PSU & Neg.Apr 78 Audio Delay Line & Neg.Apr 78 Gas Alarm & Neg.May 78 White Line FollowerJune 78 Neg.Apr 79 Note:C

May 78 Acoustic Feedback EliminatorJune 78 Neg.

May 78 Add-on FM TunerJune 78 Neg.

June 78 Audio AnalyserJune 78 Ultrasonic Switch & Neg.June 78 Phone Bell Extender & Neg.July 78 Proximity Switch

Aug 78 Neg.July 78 Real Time Analyser MK II (LED)Aug 78 Neg.

July 78 Acc. Beat Metronome.Aug 78 Neg.

July 78 Race TrackAug 78 Neg.

Aug 78 Sound Meter & Neg.Dec 78 Note: N

Aug 78 Porch Light & Neg.Aug 78 IB Metal Locater & Neg.Aug 78 Two Chip Siren & Neg.Sept 78 Audio Oscillator

Nov 78 Neg.Sept 78 Shutter Timer

Nov 78 Neg.Sept 78 Rain AlarmOct 78 CCD Phaser

Nov 78 Neg.Oct 78 UFO Detector

Nov 78 Neg.Oct 78 Strobe IdeaApr 79 Note:N

ISSUEDATE

Nov 78 Cap Meter &Neg.Nov 78 Stars & DotsNov 78 CMOS Preamp & Neg.Dec 78 Digital Anemometer

Feb 79 NegMar 79 Note:C. D

Dec 78 Tape Noise ElimFeb 79 Neg

Dec 78 EPROM ProgrammerFeb 79 Neg

Jan 79 Log Exp Convert.Feb 79 Neg

Jan 79 Digital Tach.Feb 79 Neg

Jan 79 FM TransmitterFeb 79 Neg

Feb 79 Phasemeter & NegFeb 79 SW RadioFeb 79 Light Chaser & NegMar 79 Tape -Slide SynchMar 79 Synth. Sequ.Mar 79 Dual DiceApr 79 Solar ControlApr 79 Audio CompressorApr 79 Wheel of FortuneMay 79 Light ControllerMay 79 AM TunerMay 79 VHF Ant.June 79 Easy Colour OrganJune 79 LCD ThermometerJune 79 Light Show Seq.June 79 VHF Ant. 2June 79 Bip Beacon

ARTICLE

PROJECT FILE is our department dealing withinformation regarding ETI Projects. Each monthwe will publish the Project Chart, any Project Noteswhich arise, general Project Constructor'sInformation, and some Reader's Letters andQuestions relating to projects.

PROJECT NOTESSince this magazine is largely put together by

humans, the occasional error manages to slip by usinto print. In addition variations in componentcharacteristics and availability occur, and manyreaders write to us about their experiences inbuilding our projects. This gives us informationwhich could be helpful to other readers. Suchinformation will be published in Project File underProject Notes. (Prior to May 78 it was to be found atthe end of News Digest.)

Should you find that there are notes you wish toread for which you do not have the issue, you mayobtain them in one of two ways. You can buy theback issue from us (refer to Project Chart for date ofissue and see also Reader Service Information onordering). Alternatively you may obtain a

photocopy of the note free of charge, so long asyour request includes a self addressed stampedenvelope for us to mail it back to you. Requestswithout SASE will not be answered.

Component Notationsand UnitsWe normally specify components using an

international standard. Many readers will beunfamiliar with this but it's simple, less likely to leadto error and will be widely used sooner or later. ETIhas opted for sooner!

ETI Project ChartPROJECT CHART

This chart is an index to all information availablerelating to each project we have published in thepreceding year. It guides you to where you will findthe article itself, and keeps you informed on anynotes that come up on a particular project you areinterested in. It also gives you an idea of theimportance of the notes, in case you do not havetheissue refered to on hand.

Canadian Projects Book

Audio Limiter5W StereoNotes N, 0 May 79OverledBass EnhancerModular DiscoG P PreampBal. Mic. PreampCeramic Cartridge PreampMixer & PSUVU Meter CircuitHeadphone Amp50W -100W AmpNote N May 79

Metal LocatorHeart -Rate MonitorGSR MonitorPhaserFuzz BoxTouch OrganMastermindDouble DiceReaction TesterSound -Light FlashBurglar AlarmInjector -TracerDigital Voltmeter

Key to Project NotesC:- PCB or component layoutD:- Circuit diagramN:- Parts Numbers, SpecsNeg:- Negative of PCB pattern printed0:- OtherS:- Parts SupplyT:- TextU:- Update, Improvement, Mods ':- 1Jotes for this project of complicatednature, write for details (enclose S.A.S.E., see

text)


.S:::W:::::::W.Ceni*MM.:WASftsmift{MSSZSOWSOM,

Firstly decimal points are dropped andsubstituted with the multiplier, thus 4.7uF is written4u7. Capacitors also use the multiplier nano (onenanofarad is 1000p F). T hus 0.1uF is 100n, 5600pF is5n6. Other examples are 5.6pF = 5p6, 0.5pF = Op5.

Resistors are treated similarly: 1.8M ohms is1M8, 56k ohms is 56k, 4.7k ohms is 4k7, 100 ohms is100R, 5.6 ohms is 5R6.

Kits, PCBs, and PartsWe do not supply parts for our projects, these

must be obtained from component suppliers.However, in order to make things easier we co-operate with various companies to enable them topromptly supply kits, printed circuit boards andunusual or hard -to -find parts. Prospective buildersshould consult the advertisements in ETI forsuppliers for current and past projects.

Any company interested in participating in thesupply of kits, pcbs or parts should write to us ontheir letterhead for complete information.

READER'S LETTERS ANDQUESTIONS

We obviously cannot troubleshootthe individualreader's projects, by letter or in person, so if youhave a query we can only answer it to the extent ofclearing up ambiguities, and providing ProjectNotes where appropriate. If you desire a reply toyour letter it must be accompanied by a selfaddressed stamped envelope.

PLEASE NOTE: WE CANNOTANSWER PROJECT QUERIESBY TELEPHONE.


MARKETPLACEHey! Where are all those ads? This isFREE you know. All you have to do iswrite what you want to buy/sell/swap onthe back of a postcard or empty envelopeand send it to: ETI Marketplace, 25Overlea Blvd Toronto ONT M4H 1B1.

FOR SALE: LM382 AND LM379 ICS TOUSE IN 5W STEREO PROJECT ETI 444$5.00 EA OR $9.00 FOR BOTH. M.BERNIER, 12896 PLAISANCE, PIERRE -FONDS, QUEBEC H8Z 1Z2

I WANT TO BUILD OR BUY A SMALLFM TRANSMITTER TYPE BURGLARALARM FOR A MOTORCYCLE. THEALARM SIGNAL IS TO BE PICKED UPON A HOME RECEIVER OR BELTMOUNTED BEEPER ETC. D JACOBS POBOX 197, ARMDALE, N.S. B3L 4J9

WOULD LIKE TO RECEIVE ARTICLEON RCA COSMAC ELF. ANY PHOTOCOPY WILL DO' A & S BOISVERT, 4830DES PERVENCHES, ORSAINVILLE,QUE G1G 1R7

WANTED: BOOK "THE GOLDEN BOOKOF CHEMISTRY EXPERIMENTS" WILLPAY GOOD PRICE GEORGE VISENTIN92 PETERBOROUGH AVE, TORONTOONT M6H 2L1 CALL 652 1378

ITSNow Available

ETI True RMS Voltmeter$89.95

ETI Bucket BrigadeAudio Delay Line $59.95ETI Frequency Shifter . . $69.95ETI Ultrasonic Switch . . $29.95ETI CCD Phaser $79.950-24V 1 Amp Power Supply

$19.953 Channel Colour Organ

500W SCR $19.951500W TR IAC $29.95

2W 12V Audio Amplifier$8.95

Strobe Light $14.95Light Chaser Kit (10 LEDs,Variable Speed) $19.95

Cheque, Money Order or MasterchargeInclude card expiry date and number

Ontario residents please add 7% sales tax

DO NOT SEND CASHAllow 3 weeks for delivery

DOMINION RADIO &ELECTRONICS

535 Yonge St. TorontoOntario M4Y 1Y5

AUGUSTEver wondered where to get a decent case for your projects? You'llfind the answer in next month's Box and Case Survey. Is anyonestill using TV antennas? You bet!! We tell how to choose. Smokealarms: principles of these hot items explained. Plus of course muchmore, including an Audio Power Meter project.

Next month is going to be pretty exciting for us, with the commen-cement of two new departments. Steve Rimmer continues his cover-age of what's available on your TV screen with What's On, August'stopic is TV from satellites. Meanwhile, we're going to start a write-in forum for teachers, students, any one who wants to learn how toteach or learn about electronics better (got that?). Suggestions ontechniques, neat concepts etc are invited, along with news and pro-posals for organization among electronics educators.

(The articles mentioned are in an advanced state of preparation,however circumstances may require us to change the contents.)


ReaderServiceInformation

Editorial QueriesWritten queries can only be answeredwhen accompanied by a self-addressed,stamped enveloped, and the reply cantake up to three weeks. These mustrelate to recent articles and not involveETI staff in any research. Mark yourletter ETI Query.

Projects, Components,NotationFor information on these subjectsplease see our Project File section.

Sell ETIETI is available for resale bycomponent stores. We can offer a gocddiscount and quite a big bonus, thechances are customers buying themagazine will come back to you to buytheir components. Readers havingtrouble getting their copy of ETI couldsuggest to their component storemanager that he should stock themagazine.

Back Issues andPhotocopiesPrevious issues of ETI-Canada aceavailable direct from our office for$2.00 each. Please specify issue by themonth, not by the features you require.The following back issues are stillavailable for sale.

1977FebruaryMayJuneJulySeptemberNovember

1978milimmosiejo.

FebruaryMarchAprilMayJuneJulyAugustSeptemberOctoberNovemberDecember

1979JanuaryFebruaryMarchAprilMayJuneJuly

We can supply photocopies of anyarticle published in ETI-Canada, forwhich the charge is $1.00 per article,regardless of length. Please specifyissue and article. (A special con-sideration applies to errata forprojects, see Project File.)

LIABILITY: Whilst every effort has been made to ensure that all constructional projects referred to in this edition will operate as indicated efficiently and properly and that all necessarycomponents to manufacture the same will be available, no responsibility whatsoever is accepted in respect of the failure for any reason at all of theproject to operate effectively or at allwhether due to any fault in design or otherwise and no responsibility is accepted for the failure to obtain any component parts in respect of any such project. Further no responsibility isaccepted in respect of any injury or damage caused by any fault in the design of any such project as aforesaid.

Now AvailableOUR ALL NEWLENLINEELECTRONICCOMPONENTSCATALOGUE.

60 pages containing more than400 items, allfully illustratedand described.

SEND FORYOUR FREECOPY TODAY!

rPlease send me your LENLINE Electronic Components1Catalogue and the name of my nearest LENLINE Dealer.

IL

NAME

ADDRESS

CITY

PROV CODE

len finkler ltd25 Toro Road, Downsview, Ontario M3J 2A6 630-9103

Advertisers' Index

Allan Crawford Associates 7

Alpha Tuner Service 64

Classified Ads 71

Dominion Radio and Electronics 73

Gladstone Electronics 20

H. Rogers Electronic Instruments 55

Jana Industrial Electronics 66, 67

Kyll Electronics 11

Len Finkler 14, 20, 74

Motorola 66

McGraw-Hill 75

Sprague International 76

Webster Instruments 13

Zenith Radio Corp. 62


New from NRI! 25"color TV thattunes by computer,programs anentire evening'sentertainment.

Just part of NRI'straining in servicing TV,

stereo systems, video tapeand disc players, carand portable radios.

Only NRI home training prepares you

so thoroughly for the next great leap forward

in TV and audio...digital systems. Already,

top -of -the -line TV's feature digital tuning,

computer programming is appearing, and new

digital audio recording equipment is about togo on the market.

NRI is the only home study school to

give you the actual "hands-on" training you

need to handle servicing problems on tomor-

row's electronic equipment. Because only NRI

includes this designed -for -learning, 25"

diagonal color TV with electronic tuning,

built-in digital clock, and computer pro-

grammer as part of your training. With this

advanced feature, you can pre-program an

entire evening's entertainment...even key lockit in to control children's viewing.

ExclusiveDesigned -for -learning Concept

The color TV you build as part of NRI'sMaster Course looks, operates, and performs

like the very finest commercial sets. But behind

that pretty picture is a unique designed -for-

learning chassis. As you assemble it, you per-

form meaningful experiments. You even intro-

duce defects, troubleshoot and correct them as

you would in actual practice. And you end up

with a magnificent, big -picture TV with ad-vanced features.

Also Build Stereo,Test Instruments

Thats just a start. You demonstratebasic principles on the unique NRI Discovery

Lab® then apply them as you assemble a fine

AM/FM stereo, complete with speakers. You

also learn as you build your own test instru-ments, including a 5" triggered sweep oscillo-

scope, CMOS digital frequency counter, color

bar generator, and transistorized volt -ohm me-

ter. Use them for learning, use them for earn-

ing as a full- or part-time TV, audio, and video

systems technician.

Complete, Effective TrainingIncludes Video Systems

You need no previous experience of any

kind. Starting with the basics, exclusive "bite -

size" lessons cover subjects thoroughly, clearly,

and concisely. "Hands-on" experiments rein-

force theory for better comprehension and

retention. And your personal NRI instructor is

always available for advice and help. You'll be

prepared to work with stereo systems, car

radios, record and tape players, transistor

radios, short-wave receivers, PA systems, musi-

cal instrument amplifiers, electronic TV

games, even video tape recorders and tape ordisc video playbacks.

Send for Free Detailed CatalogMail the postage -paid card today for our

free 100 -page catalog with color photos of all

kits and equipment, complete lesson plans,

convenient time payment plans, and informa-tion on other electronics courses. You'll also

End out about NRI's new Computer Technol-

ogy Course that includes your personal mi-

crocomputer. Or Complete Communications

with 2 -meter transceiver. If card has been

removed. write to:

NRI SchoolsRI McGraw-Hill ContinuingEducation Center

330 Progress Avenue

Scarborough, Ontario MIP 2Z5nis or telephone 416-293-1911

Now from Sprague...

The ultra -thinfilm capacitors

you've been asking for.

Low-cost Verti-Film* epoxy -coated polyester -filmcapacitors help you beat the cost/space squeeze whenservicing imported communications and entertainmentelectronic equipment, letting you make exact replace-ments on crowded PWBs quickly and easily. Theirsingle -ended design permits vertical installation in far* Trademark

2x ACTUAL SIZE

less space than required by conventional axial- orradial -lead film capacitors.

Rated at 100 WVDC, Verti-Film Capacitors range incapacitance values from 0.001 to 0.47 tif with a toler-ance of ±10%. Get Verti-Film Capacitors from yourSprague distributor.

For the name of the Sprague distributor nearest you, write or call:

TRANS CANADA ELECTRONICS LTD.1900A Eglinton Ave. EastScarborough, Ont. M1L 2L9Tel. (416) 757-4171

P.O. Box 117, Dollard DesOrmeaux, Que. H9G 2H5Tel. (514) 747-4266

YOUR NUMBER 1 SOURCE FOR ELECTRONIC COMPONENTS

SMITH-PATTERSON & ASSOCIATES1120 Hamilton St. 489 Kensington St.Vancouver, B.C. R3E 211 Winnipeg, Manitoba R3J 1J8Tel. (604) 681-0743 Tel. (204) 885-1376

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THE MARK OF RELIABILITY

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