VHFCOMMUNICATIONSEspeciaity Covering VHF, UHF and MIcrowaves

A Publication to, the R3dio Amateur World'Nidi!

IF.dition 3/199.5

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VIII'C( IMMUNICATlO!VS

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VHF COMMUNICATIONS 3/95

Contents

Luis C up idoen DMK

Michael KuhnenH6NT

Malja z VidmarS53M V

Dipl.-Ing Delle! Burchard

Ra iner Sc hmullingDK6ZK

Frequency Co unter with Harm onicMixing for the UHF/SIW Am ateur

200mW (iaAsf ET Amplifierfor 24 GJIz

A 1)IY Receiver for GPS andGI.()N ASS Sate llite..Part-6

Linear Signa l Recti ficationPart-I

Expanvion and Asse mbly of theDRIN V Spect rum Analyser

130 - 146

!47 - 1."2

153 - 167

1 6~ - 171)

UIO - I RX

(if; KM Publications, 5 Ware Orchard, Barby, Rugby, CV23 8UF, UK

Telephone: lO) 1788 890365; INT: +44 1788 890 365; FAX: (0)1788891883INTERNET: vhf·comm@g6iqm.demon.co.uk

COMPUSEAVE: 100441,377

129

VHFCOMMUNICATIONS 3/95(~--- -----------'-"'-"===="'"

Luis Cupido, CFID MK

Frequency Counter withHarmonic Mixing for theUHF/SHF Amateur

T aken from an address gtvcn to theVl-I F/UIIF/ SIIF Technical Congress'94 in Munich

Amateurs huilding their own radio­Frequency assemblies an d equipmentalways need at least II minimuma mount of measurement and rcsnngequipment. This is particularly truefor SHF operators. where there is notmuch measurement equipment avail­able and pric es arc high. The Ire ­quency meie r described below canmeasure up to 2(j-S GH z (or even 33GIb ,) with a resolution of 100 Hz,lind with a constant sensnt vny tlf • 10dBm .

equipment is required for the increasinglevel s of activity a bove 1.3 GITl..

A number of different procedur es areavailable for frequency dc tcrrrunarion ,e.g ., using wave meters, cav ity resona­tors and downwards converters with aknown local oscillator frequency. Thesetechniques ean prov ide results whichcan certa inly he of lise. Hut beca use ofthe poor resolution, in particu lar for thedownwards convers ion proced ure, theyare not very practical for a receiver.

1.1. Brief Descr-iption of FrequencyMeasurement Proced ure

J.INTR ODUCTION

It is well-kn own that there arc reasona­bly-priced, ready-to-operate frequencycounters which operate at up to 1.3GHz, Howeve r, addit iona l measurement

Several procedures can he used tomeas ure frequencies (only the essentials<Ire dealt with here) .

• Lo w frequencies (anything below 10MITz) can be measured hy countingthe number of periods over a fixedtime (1 second for a resolution of 1IT....). This procedure is descri bed asthe direct counting procedure (T fL­LS and CMOS technologies can beused).

130

VHF COMMUNICATIONS 3/95

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• Fo r me asureme nts at high frcqucn­cics . the range o f direct-co untingfrequ ency counters can he expandedthrough the usc of a pre-dividerus ing t-Ct. tec hnology. with whichthe input frequency is divided hy afactor. in general. of 10, 100, 64,12R or 256. Thts procedure can heused only up to the maximumoperating frequency o f the dividerused. Although 14-(JHz pre-dividersarc av ailable on the market they arevery expe nsive and arc beyond thereach of amateurs. Cheap pre-d ivid­e rs do exist, with whieh d ivision canbc Zcarr icd out at lip 10 2.5 <ill/,How ever, most o f them are fordynamic operation only - i.e . laidout a s from a minimum ope ratingfrequency. so that they can be usedfor only a few band s.

• Frequency measurements on micro­waves ca n he carri ed 0 111 with (he

help o f wave mete rs and cavityresonators at low reso lution .

Measurements using the counting pro­cedure are possib le only if the signal isconv erted to a lower intermedia te fre­quency. which can then he mea sured bydirect counting. l o is can he done us in~

the following procedure:

1. Interference method using a simplesuperheterody ne receiver to measuretho: precise osci llato r frequcncy andthe intermed iate frequencies.

2. Transfer oscilla tor procedures usinga simple superheterodyne receiverwith an oscillator linked to theintermediate frequency signal whichis ill 3 constant re lationship with thefrequency of the first oscillator,which i ~ then measured .

131

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3. l la rmonicv procedure using a super­heterodyne rece iver wit h :I harmonicmixer being used as a first mixer, sothat vc'v high Irequcucics can beco nven ed to an intermed iate Ire­qllt'IlCY . The 1II11l1Ocr of harmonicsthe n also has to be calculated todetermine the frequency of themea sured signal.

1.2. Frequency Meter )IS perI Iarmonlc M ixing Pr-inci ple

'n lis pr inciple was selected for thcmicrowave frequency counter, in p:lr­ticular, because it is the on ly princi plewhich can be used to measure hightrcqucnclcs using cheap co mpone ntsand local (first) oscil lators (1 , LO )below I GIll, which can easily heassembled by any e xperience d amateur.

The radio -frequency section of thecounter consists 0 ]" a harmonic mixerand the intermed iate freq uency sect ion(sec bloc k diagram. l-ig. f ), To carry 011I

the measurement. the first oscillator isswept th rough until a strong lntcr r ncdi­ate-freq uency signal appears. The firstosci llato r is then locked and the inter­mediate frequency is measured andstore d. The first oscillator is thenstepped up by a small amount (c .g. Ikllz) and the intermediate frequency ismeasu red again to calculate the inter­media te frequency shift and the direc­tion o f deviation. The ordinal numberof the harmonic can then be determinedby divid ing the LO shift by the inter­

' med iate freque ncy shift (e.g . if the shiftis 12 kllz then n =12/ l =12).

The conversion side hand can be deter­min ed by exami ning the direc tion of

the intermed iate-freq uency deviation (ifdownwards: USB. if upwards: 1.s13).

Finall y. the measured frequency, f:am ounts 10 :

f = LO ± ffF

The procedure descr ibed presupposesthat a comp uter-cont rolled frequencyCOU Jl!cr is availa ble. However, nowa ­days mtcro-cor arouers arc simple to useand arc sufficiently powerful to can)'out the calculations for our applica­tions.

2.CIRC UIT DESCRIPTION

The circuits arc certai nly extensive. n utthey arc not difficu lt to con.srrncr. Nordo they pose any special calibrationprob lems. The equipment is built lipfrom severa l e xisting assembliesOSC2's, AMP02/01 /04 ' s and ATrot ' s.

2.1. The Harmonic Mixer

The harmonic mixer uses a BJ\T14mix ing diode (26-GBz version, with nolead s) in a single-cycle circuit . Th isGaJ\s diode is contro lled hy a 17-dBmsignal from the first oscillator in the700 - I,()()() MJI1. range.

The rapid switching characteristics ofthe BAT! 4 ma ke it possible to convertup to the 33rd harm onic of the osc illatorwith a mixing loss of app. 50 dB. Themaximum efficie ncy of the harmo nicmixer is essentia lly dependent on itsstructure, The maxim um operating Ire-

133

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134

quency of the equipment is also deter­mined by the upper operating frequencyof the harmonic mixer. The structure ofthe harmonic mixer is described later.

2.2. The Intermediate-FrequencyPre-Amplifier

In the preamplifier, the main emphasishas been laid on a low noise factorwithin the intermediate frequency rangeand on maximum suppression of the1,0 frequency. which is extremely un­desirable in the intermediate-frequencycircuits. This assembly comprises aChchycheff bandpass filter. followed bytwo AMP02 amplifiers. with an ampli­fication of more than 25 dB in theintermediate-frequency range of 50 ­350 MHz. The amplifier assemblies useBFR90A transistors. At the output ofthe second amplifier. a signal weakenedby - 10 dB is decoupled to an externalintermediate-frequency output. whichcan be very useful.

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Amplifie r And AGe

In thi....tage. thc ..ignal supp lied by thepreampli fier is am plified to the level o f() d Bm required for the proccs-ln g inthe subsequent d igita l circuits. T heintermedia te-frequency amplifier is 4­stage . built for a total amplificat ion ofmore than 45 dB. To ma intain acons tant output leve l. the final stagecontains an i\(: C detector to comrott hcAGC circuits•. Th i.. amp lifier mu ..t havea flat frequency response i!l the 50 ­350 M IIJ. range and ..ho uld have uslill ie noise a.. possible, so as to improvethe operating thres hold of the vubsc­quem d igital ci rcuits.

T he dyna mic range of this intermediatefrequency naturally has to be greaterthan the dynamic range wh ich wou ld bedesira ble for any kind o f input fre­quen cy. The reason for this lies in thefact lha l the mixed attenuation of theharmonic mixer changes from 7 dB 1050 d B for the higher harmonics.

The bes t operating resu lts for thefrequency counter could he achieved ifme intermedia te- freque ncy amplifierhad so mu ch tota l amplifica tion that ano ise sig nal would he suppl ied at itsoutput which was so high Ih31 it couldbe proccv..ed d irec tly by the digitalc ircuit s. This happens at a level ofappm xi1ll3tcly - 10 to 0 dBm. at theinput o f thc next stil!!c.

Signal-, ;In-we the not-e arc count ed,uhh ough the dyna mic range of the H_'Linput to the ncx t slavc i ~ narrow. So itiv de..irablc to have 3 constant-levelsignal availahk at the output of theinrcrmcdi atc-Ircq u...ncy section forcvay ,i~ nal at a level whic h i~ con cid-

erably higher than the noi ..e lc vcl. Thi sis brought about by an aut omatic ga incontro l ('\GC) . which opcrerec ove r :I

wide ran ge and ma kes good levelcompensation possible.

Signal limiters o r limit er amplifiers arcnol desirable here. as to a large extentthey generate harm onics which canimpa ir the dig. ital circuit func tions.Reme mber. that with an inte rmed iate­frequency signal of 50 Mill' the har­monics arc in the 50 - ]50 MH .-:mcesnremcr u range . Th e A( ie ' s widedynamic ra.ngc is ohtained throug h thecontro l o f a I'IN.<Jiode attenuating. cle ­ment with which ove r 70 dB of aucnua ­tinn C3n he attain ed.

The i\Ge circuit is very simple andeffective. Here the intermediate-Ire ­quency level is compensated using aDC CIITTent (adj usted at R V3( 1). so thatthe comparat or (a lso used as an integra­tor) closes the control loop through theaucnuat lng elemen t. The AGes re­sponse li me is in the orde r or 10 r ns.

The AGe ..ignal is fed into the m.• . v

processor for the imcrmedia te -frc­qUt'ney level 10 he evaluated . An LEtcolumn disp lay pro vides an indic atjorof the siJmal level . deri ved from thei\GC signal.

2A. T he P r e-Divid er

Th iv part of thc c ircuit serve, only tcbrill!! the intermediate Incqucrwy to alevel which lies within the operatingrange of digital C MOS ci rcuits. On lyan Eel. d ivide r from Telefunke n isused in the circuit (others could havebeen used as wcll ). The pre-divider i.ssupplie d wuh a 0 dB m signal and

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The osc illator. the frequency of whichcan hoc varied ove r a wide range. uses amicro-strip transmission circuit. It isfollowed by an amp lifier which sup­plies the output level required .

One pout of the osc illator signal. auenu­atcd hy 20 dl! by a PBSSI C pre-

2.6. Ana IOJ!: IIl.·lJ) iJtilill Co nver sion orIn termediate-Frequency Level

The AGe signal is initially processedin an analogue circuit 10 improve thereal rang e of the An converte r (rcruem­her that the attenuating element in theinte rmed iate frequcncy/A( ;C branchdisplays a very strong ly non-linearatt enuation gradient ). Additjonal com­po nents arc needed to send a ~ i !,-na l 10the micro -processor in case of satura­tion.

2 .7. T he Fir sl (L OCHI) Oscttlaror

lhc first oscillator has to supply 3high-leve l high-fre que ncy signal (+ 17dftm) to control the harm onic mixer.

divides by 64. A TIT -T.S inverterconverts the signal (0 the TTL level.

2.S. T he Counter Sect ion

Here the intermcdiatc -Ircquency signa l.a lready div ided, is fed to an Intel 8254Ox t 6 bit counter). which i:s direc tlycontro lled by the micro-processor.Co unters 0 and 1 arc cascaded to makea 32-hit counter resolution possible .whilst counter 2 is used as 3 one-s hotfor the input gate control. The micro­processor controls all 3 counters di­rcctty .

The reference frequency for controllin gthe high ly precise trigger signal isgene rated by dividing a 4-Mllz signalwhich is supplied by a thermosta tically ­stuhiliscd crystal oscillator. which isnot mo unted on the printed circuitboard .

139

(~. VHF COMMUNICATIONS 3/95

Fi~ . R: l he Prototype uni t with the easily idcnt lrla bfc CPU Beard

divider , is fed to a dual-m ode SPS727pre-div ider. which is contro lled hy aPLL-IC NS8242.

The NSR242 1'1.1 . module (Plcsscy) is J

dua l-mode PI J Ae with seTi:!1 controlinputs and two phas e detectors. Mo­toro!a modu les can also he used, billsoft ware changes arc required.

Th e PI .L·le uses the S3 111 l' exte rnalre ference signal of 4 MIIJ .::I S theco unter sect ion. In the loop Filter . anOJ' am plifier is used in IIIl' d :ls..k way.In ad dit ion , a cons iderably narrower

filte r run be wired up. if the userselects 11w cou nt dw ell period til obtaina cons idera bly purer LO spectru m.Because of this characteristic. the fTC­

l.j IlCnl'Y counter can be used as arecept ion converter.

An I.ED is provided to light up when

140

the PLL is engaged. But this is neede donly for the rcsun g and calibrationprocedures.

2.8. Th e Mlcro-Cont rotler

Cont rol and freque ncy counting requirethis equipment 10 have funct ions in­volvin g the making of deci sions andfixed po int calculations with n ·bitresolution. This makes it absolutelynecessary to usc a micro-corurotlc r.

A programmable RO.U board generallyobtainable from component suppliers.R.S . ctc .. is used as mic ro-c ont roller.This boa rd has ru 8031 with un RS212interface, an 8255 PPI. an 8· 1.: RAMand a 16·l ROM. 100'1 · compatibleboards can he set up how you like.provided the following addressing dataare incl uded:

VHF COMMUNICATIONS 3 '95

Fig.Q: T he Lower A.....cmblics arc mou nt ed in tin- pla te h(H1 ...tngs on Ihe base

( :S5 and CS6 arc used in the intermcdi­ate-frequency level and counting as­scmblics.

In the ...witching documents. you willlind the desc ript ion s 1'1.0 to 1'1.7,corre sponding to port P I of the S01 I .whilst pon s PAn to PI\ 7 and P BO toPB7 (rese rved for the "re ference sourceconnection" option) and peo 10 r<.:7correspond 10 port s A. B and C of theS255 interface module (this is all yOIlneed to know). Commercially obtain­able boards can he used .

RO~1 address:HAM address:R25S-PPI addrcvs :

( 'S5:( ~S() :

OOO I l...40oH

XIou " AOOO) IEOIX)!I:1{Xl/I:2011and DOO Il1\0001 11l000/l

2.9. The Sottwa re

The ..o ftware requ ired for contro llin gthis frequency meter must include thesequences laid down in the nnw chan(Fig.7) . A.. wet ! as a computer core, ilmust alvo have Interfa ces to the user. sothat rnudc and reso lution can he sc­leered.

In thi.. cc r ucxt. the requirement forsimple operation has controlled thedevelopment of the so ftware. hili with ­om this lead ing to too great a loss offlexibility, It goes hcyond the Sl'Ope ofthi s art icle to des cribe or illustrat e thevarious ..o ftware development optio ns.or 10 provide the software listin gs.which arc over 10 pages long. Th esoftware was developed using C lan ­guage and take s up less than 8 kB of aROM in its comp iled form .

141

VHFCOMMUNICATIONS 3/95(t- --- ----- - -----"""-"''''''''''"'"''''''"''''''''"'''''''lmpo rtat t note: the softw are imposesno limi t on the highest frequencyavaila ble or on the number o f hermon­ics. hUI only on the number o f (display)charac ters d isplayed to the user - i.c.. ifanyo ne finds a harmonic mixer which,for example, displays a reasonablemixing loss at 76 GH 1.. then the counterwi ll function well (I my self have testedit 'll 48 GI ll,).

3.ASSE~IIl I.Y

microw ave frequencies. ATe types arerecommended, The input inductors con­sist of 1.5 turns of 0,2 mm. gold wire.on a t -mrn. diameter core, If a goodd iode and a small format arc chose n.result s can he obtain ed up to 40 Ci lll..

;1.2. The Pre-Amplifier

Tw o AMPU2 amplifier block s wlthnFR9UA transistors arc used in thepreampl ifier The filter has (0 attenuate(he oscillator frequency by more than70 d B, so it sho uld he care fully.assemhlcd. Good screening is ju..t asimportant as the filter itself here .

!\ss\'mhly shou ld not po se 100 ma nyprobl em s for <In experi enced am ateur,as the mos t crit ical sect ion operates onllHl- frequencies \ISing techniqu es withwh ich most amateurs arc fam iliar . T heharmonic mixer , pre amplifier. intermc­diutc -frequcncy section, PLL and pre­divider should be individuall y screened.Coaxia l plugs (SMB. SMC or SMA)sho uld he used to COIlJw d up theasse mbl ies. Po wer leads should alwaysrun thro uuh Iccd throug h capac itors . Allthis is normal prac tice for radio- Ire ­qucm-y asvcr nhly.

;'. 1. T he Harmon ic Mixer

1\\ this is the most critica l assembl y. itwas built d irecll y onto the hack o f ageld-plated S\-L\ ja ck wn h :I recrangu­lar flange. The components are solderedto one another witho ut feed wires, a llwithin <I n area of 2: x 2: mrn. on theearth ..ide o f the flanged bush. Allcomponent s are in SMD format and thecupachors shou ld display low losses at

142

.' ..', The IF/AG e Asse mh ly

The att enuating clement and the 4amplifie r stages o f the intermediate­frequency amplifie r arc simp ly asscm­hied one behind an other in a shieldedbox , together with a sp..-cl mcn printedcircu it boa rd (2 x 5 cr n.) for the AC;Cr-ircuit. Normal radio -frequency asscui­bly techniques should Ill: used .

;104 . T hl' Pre-Di vid er

A spec imen printed circuit board can heused. The levels applied <In' () dllm inthe 50 - 3:')0 Mill, rangc. Norma lradio- frequency assembly techniquesshould be used .

].5. T he F ir sl O S4: ilh.for Mnd th l'PI.1.

T he first oscillator. cOl1si'it inp o f anOSC2 sta ge. use s a BFRQli\. It isdir ectly followed by an amp lifier stage

VHF CO....UNICAlIONS 3195

I!~H­

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:> 1"U 'tl IL - ,'tl 0. 1o VI ;

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143

VHF CO MMUNICATIONS 3/95

Once the equ ipment has been assem­bled and the power supply voltageshave been checked, the equipment canbe powered up. It should be apparentthat the soft ware has started to operateimmediately. and a start messageshould appear on the display unit. Anymalfunctions occurring at this stagemay he due 10 wrong connections onthe micro-processor or interface mod uleside or to damaged modules, for exam ­ple in the ROM or the RAM. AI allevent s. no further help can he givenhere. In the next stage, the PU ./firstoscillator function is checked, as it isindependent of the other radio-fre ­quency sections . Equ ipment for meas ­uring the power and frequency in therange between 0.5 and 1.5 Gl lz isneeded here .

4.T ESTING A:'oIf) CAI.I BRA­no:'>

3.7. The Keyboard and DisphlYAssemhly

This can he built lip however you likeon the front panel. No critica l circuitsarc used (Fig. I0).

3.6. The Cou nter and IF Level/ADConver te r Assembly

Only high-level low-frequency signalsarc used in this assembly, so that it canbe constructed usi ng normal printedci rcuit boards O( wire-wrap technolo gy.

(~---:-------:-------========with the BFR96S. Good S~D capaci-tors should be used here. The pre­divider, the PLL· IC and the OP ampli­fier OPA MP are assembled on thesurface of a standard board 10 producea good earth connection. !I. shieldingplate should be provided betwee n theosci llator, the amp lifier and the digitalci rcuits.

3.8. The Master OstillHloT

Va rious osci llator circuit s can be found

in the literature . How ever. for op timalope ration a thcrmostat-stabihsed osc il­lator Is recommended. Surpl us units canalso he very suitable.

3.9. The Powe r Supply

The requirements for operating thisfrequency counter are simple: + 12V/O.35 A, + :\ V/fl.6 A, - 5 V{!5 rnA. +24 V/5 rnA. This article does notdescribe the power supply.

4.1. l'L1 i F!rst Oscillalor Test

The tuning voltage should be isolatedfrom the oscillator and checked bymeans of an externa l power source or avariable resistance . During tun ing. he­tween I and 20 V, a minimum tuningrange of 650 - 1.050 MHz should heattained, and the output level should heat least 0 dlim . This level can he setwith the help of the trimming resistorin the bias voltage circuit of theAMP05 amplifier. Monitor the tem­perature of the BFR96S during this test.The tuning voltage is then re-connectedto the origina l circuit . As the programis runn ing. the cou nter is in search

144

VHF COMMUNICATIONS 3/95

mode > i.e . the control volta ge shouldsweep the osc illator through. A saw­tooth signal should be obse rved at pin-6of the TL081.

4.2, Pre-Amp tttl cr Testi ng

A. prcampli fication of more than 25 dBand a 50 - 350 :v1t11. band width shouldhe meas ured in this asse mbl y. Nospecia l les t procedure is called for. Thepreamplifier can he optimised by SCI­

ling the trimmi ng resistor at any stage.

4.3. IF/AGe TeslinJ.:

A spect rum analyser is of great use inthe calibration of the intermediate fre­quem'y/An C stage. The ' assembly isconnected to a spectrum analyser. TheRV301 trimmi ng resiste r shou ld heturned up to max imum (in the directionof the R306 resistance). This causes theattenuating e lement to dis play the low­est level o f atte nuation. Th e tota lampli fication for a ll stages should thenbe app . 48 dB. Calibrating each indi­vidu al stage then improves the am plifi ­cation and phase behaviour. Make surethat the ga in slope and the output noiseare constant over the 50 - 350 ~I "'.

range . The coil s in each stage should here-adju sted to obtain a flal gradient.

The input of the intermediate-frequencysect ion is then connected to a radio­frequcncy gene rator at ISO MHz and atan output level o f . 60 dltm . The signalleve l h men raised until a 0 dBm signa lappears at the output. The RV30ltrimming resistor is then slo wly ad­justed until the AGe responds. Mon itorthe AGe voltage gradie nt while the

4.4 , Pre-Divider

Connect the pre -divider to the intermc ­d iatc-Ircquency section and use theradio-frequency generator in the sameway as when testing the intermediate ­frequency section in A(jC mode. Thepre-divider output should always supplya clean square -wavc signa l.

4,5, The Counter Assemhly

This assem bly doc s not need ca librat ­ing, Only the gate pulse shou ld beobserved. When not in searc h mode, itshou ld display steep flanks if theequipment is functioning correctly.

4,6. IF Level/AD Convert er

Thi s stage shou ld be set in such a waythat it sup plies 0 - 1 V at the Arco nverter input. This is obtained b)adjusting RV601 over the full AC3Crange . I recommend that the radio­frequency generator should he left con­nccted to the intermediate-frequ encysection and the radio-frequency outputshould be switched on and off. Whenno radio-frequency signa l is applied, avolta ge of 1.050 V should he observedat pin-6 of the Ie U60I. l-or theadju stment of RV602, the refe rencevo ltage of the AD conve rter should heser to 0.5 V,

145

(~ -----------'-"'--""'''''''''==''-'''-'''4.7. Final Test

Assuming that nothing has gone wrong,the frequency counter should now becapa ble of operating. The sensitivity ofthe equipment can now be checkedwith the help of a calibrated meter. Ifsomething is wrong:-

If the frequency counter docs notoperate satisfactorily. you should be ina position 10 identify the problem.

If the unit searches for a signal butnever locks on, the most probablereasons arc:

Non-functioning of AGe, no binaryoutput signal s on AD converter or nointermediate-frequ ency signal (har­monic mixer uot working).

If the unit searches for a signal andlock s on, hut the display data varie shetween wide margin s, the wiring inthe cou nter section or the CPl J sectionis incorrect, or something is wrong withthe reference signal.

If the unit ' s functions collapse and areno longer available for operation, thewiring of the digital section should bechecked.

5.OPERATION

Only 4 keys are used to operate thefrequency counter. In the format de­scribed, the frequency counter is laidout for fully automatic operation andthe user has only to select the resolu­tion and the mode.

The keys > and < are provided for

146

converting the resolution from !OO Hzto I MHz.

The "Search" key switches betweenautomatic search per measurement andone search cycle per measurement. Inthe automatic search mode, the fre­quency counter goes into the searchmode after each counting procedure. Inthe indiv idual mode, the frequencycounter searches and; if it finds some­thing, it continues to count until thesignal disappears.

The "Ho ld" key holds the display andthe narrow-band lock mode of the PLI.is set. In this mode, the equipment canbe used as a receiver input stage.

6.CONCLUSIONS

Severa l improve ments arc beingworked on at the moment and ifrelevant they will be made public at alater date. The prototype has now beenworking for a year, retaining the origi­nal specifications. Most components arcwired up on specimen printed circuitboards or arc in a wire-wrap format.Any co-operation or any joint effort tosimplify the reproducibility would beinteresting. I am also interested inhearing any observations concerni ngthis project.

My special thanks go to DJICR, MuxMunich, who was responsible for theselection of RAT14, which made itpossible for me to obtain the optimumcharacteristics from this equipment .

VHF CO MMUNICATIONS 3/9 5

Michael Kuhne, DB6!JT

200 mW GaAsFET Amplifierfor 24 GHz

Mltny station.. have been constr uctedfor Ihe 2,J-GI IL hand In recent yea rswhich can J:(' neral(' Iran sm il powerI('vels rlln~in~ from a Iew 100 j.lW 10R m aximum of )00 mw. These valliescould he obtained using low-costIr Knsi<;lors (sctected MG F no...' parKI­Jel}, T he powcr gai n th us obta lned fora 100 mW PA with MGF 130.'\ wasa pprox lRllllr ly 1:\ dB.

I.INTRODUCTI ON

In this article, a 200 mW amplifier willbe descri bed with an amplificat ion of20 dB. R .R0l6f ll and RRO:!(IFIlK-nand Power R~T's arc used here.from the Fuji tsu (.'ompany.

Insjde the N Gllz Amplifier

147

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II_JO p tr

1,70

DB 6NT U G\~1J..·,~'-~--'-~1L1" 1, U" l~' k UG4T' k 1100 0

Ffg. t : Cirell i! Dtazram of the 24 GUt Amplifier

-0--."

· 12V

JUT

Building 24-GIIz amplifiers calls forgreat expe rienc e in t-he SHF range andfor a lot of patience . You have to workfor every dn O[ mW when you 'reca librating. using "little nags" andputting MUS foam and copper stripsint o the housing!

2.TilE A~1PLlFIERCIRCUIT

Fig. I shows the 24-GHz amplifier cir­cuit. Th e amplifier is built on a 0,25mm . thic k Teflon printed c ircuit hoardmade from RT/duroid 5870. Stage s T1and '1'2 are connected to one anothe rthrough son strip line s and coupl ingcapacitors. and are capacir ivc ly tunedby me ans of soldered-o n " Little flags",

The para llel high-level stages with T3and '1'4 are connected to one anotherthrou gh four "./4 coup lers. This circu itopt ion makes it po ssible to obtain gooddecoupling without feedback between

the two end transistors, and makes aconsiderable contribution to the: stabil­ity of the circuit. Should any asymmc­try arise in the power stages, the radiofrequency output this generate s is ab ­

sorbed in the resistor connected toport-a . These 47 - 50.0 resistors on thecou plers are small STIr types - 1.4 x1.4 mm. format. Di-Cap capacitors areused as coupling capacitors between thestagcs.

The nega tive voltage for the r ET's isgenerated thr ough an MKlJ 55 hybridmodule . This is laterally faste ned to theinternal wall of the tinplate homi ng. Atthe output, the circuit has a directionalcoupler with a BAT 15-03W SM DSch ottky diode from Siemens . Thepowcr deliv ered can be monitored atany tim e at this test output using amoving coil instru ment.

The 1-1. 101 diodes are SMD Scho ttkydio des and help to dela y a breakdownof the rET's in the event of anyshort-circu iting of the cou pling capaci­tors. SMA 3.5 mm . microstrip connec­tors shoul d be used as coaxial jacks.

148

= = ======------- ------(+

-FI~.2a : Coa xia l For mal Te non Printed Circ uit Board

3.ASSEMBLY

The amplifi er van he assembled ineither a wave guide or a coaxialversion. Different housings and printedcircuit boards arc used in each case .

First the 0.25 mm. thick Teflon print edcircuit board (Fig.Za. coaxial form at) is

1

L~-

cui to dim ension, drilled and throug h­hole plated. 0.1 rnm. copper foil shouldhe used for thro ugh-hole plat ing.

The printed circuit hoard is now in­serted into the aluminium housing as adrilling jig and the appropriate b oresare drilled in the housing. The wmf'O'nents shown in the layou t diagram(Fig .2h) arc now placed 0 11 the trackside (top) of the printed circuit board.

...

""

FI~.2h : Component Layout for the 24 (j Ib. Ampliliu (tmesse ' = ear lh)

149

,

r--- - - IS- -

r-,"~

+.-8._},

The BAT 15·{)3W diode is soldered"overbead" 10 obtain lower housinginducuvity levels .

Before being put into the housing. theprinted board assembly should bewashed down with \p irit and thenaligned straigfu 10 guara ntee thai il isinstalled Ilat . T he underside of theboard is coaled with heal conductingpaste in the ce ntre to Improve the healdissipation from the FEr!>. The cou­pling and decoupltng side of the printedcircuit board is coaled with a secondadhesive from below. Opt imum mount­ing is obtained by pressing on theprinted circuit hoard while rhc adhesivedriess. This operating procedure must hequick and precise. as the adhesive driesvery quickly and no changes can be

made 10 the printed circuit board'sposition tberea ner. The printed circuit

150

Fbl: .,\ :Eu mple,; of ~1ill('d

Aluminium lI ousin J.:s

,*,i18

hoard is now fastened usin~ 5 x M2screws.

As an example. Fi~ . 3 shows a millcdtwo-pan aluminium housing.

4.CALIBRATION

A power supply with fine controlcurrent limit should he used for calibre­tion . A 24·GIT-t signal source with anadjustable output and a suna blc powermeier are required for calibration. The11.; trimmer is used to sct uat. UG2 ,UG3 and UG4 individually in such away thai the drain currents given in thecircuit diagra m now.

VHF CO MMUNICATIO NS 3/95

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~.- .- ..- - ."._. .................... ess v.. ~ rv. v• • "., · ,a .~ ~.- .. v.~w..... e.s- · ~ · ..

tv.c_VOI!09O " v. ~,.,.....~ StM ... .>0 . ).5 •~IO 'S-OO vcsc .... ~ -5ooA , · •...~_v

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"Readings for Specimen Assemblies:

I' in: P out : P out : P out:Set . 1 Set. 2 Set. :lcoax WG ('OUX

O.2 mWImW2 mW5 mWIO mW20 mW

21 mW105 mW195 mW275 mW3111 mW 230 mW3lOmW 230mW

20 mW100 mW190 mW255 mW255 mW255mW

The measurements were carried out atvarious times, using the rat ings whichcan he read off from the table.

It can he seen fr om the table that thesaturated drain cu rrent to he expect edcan vary . To a tergc extent. this can betraced had: to dispersion effect s fromthe transistors.

151

An initia l output of 1011 mW wasrelia bly ohla incd from all the rigsrested . fi)t.4 ~how~ the amplificationcurve of 3 prototype,

Measu ring equi pment:

HP 435 Power Mete r with liP 8485APower Sensor. together with Midwest5.5U-20 damping unit and RosenbergerR 220-3.5 r nm. wave guide transmis­sion.

5.PARTS LIST

TI FLR 016 FujitsuT2 H .R 026 Fujitsun FLR 026 FujitsuT4 R ,R 026 FujitsuDl BAT 15-0]W Siemens3 x LL 101 SMlJ Schottky diode1 x 780R1 x IN4001I x MK{1554 x IkO Minitrimmcr3 x 47n SHP type. Rohrer. Munich2 x 4700 02043 x 110 SMO

152

VHF COMMUNICATIONS 3/95

,,, c ., ~ "jr J!; .4 :

l ! MtKsurtmenl Cur ve20 ror II. pro toty pe

"

.u

I x tRW S;\tOI x 10~ tantalum S;\tOI x I nF SMD1 x 100 nF SMI>3 x Di-Cap 0.2 - 0.5 pF2 x I IlF-Df. threaded

Printed circuit hoard s for coaxial orsemi-conductor assemblies, togetherwith MKlJ55 hybrids for generatingnegative vonagc. can be obtained fromthe author.

6.LITERATURE

(I ) OCOOA: Assembly andCalibration of 24 GIll AmplifierModu les using Wave GuideTechnology as per DB6NTCongress Volume. GH1. CongressDoreen. 5. 2. '94

(2) Assemblies for 24 GillDubus. no. 4/1993

(3) Iffi9M:IN: 200 lOW GaAs FETHigh-Level StageVlfF·U JIF Congress VolumeMunich. 12.-13. 3. 94

Mmju : Vidmar. S53MV

A DIY Receiver for GPS andGLONASS Satellites

Part-6

Th is pa ri or th e ~ries continues wilhlhe cons truction derails tor the G PS!ClLO NASS Pnrhtblc Receiver CPU.the 8.kcy Keyboard. th e LCD DisplayModule and the Power Supply a ndReset cireuilry. SUj:!. j:!.cstcd mount ingar ra ngements for the var ious mod­ules arc also discussed .

·t tl C; PSfGL01\'ASS Portabl eReceiver CPU

The n!'s or OI.ONI\ SS receiv er de­scribed in this series can be built as aninterface for the nspcomputer l t l and121, or as a stand-alone portable re­ccivcr. In the tarter case the receiverneeds its own microcomputer with akeyboard and an I.CD display, Afterconsidering severa l possible ahcm a­rives. the siruplee t solution resulted inusing a suitably modifi ed CPU board nsdescribed in [I] ami [21 as the micro­computer.

The circuit diagram of the modifiedCPU board is shown in Pip!'> ,46 and 47 .Since 11 C;PS or GLO;.;rASS receiver is a

portable unit. the power consumption i.san importa nt factor and consequently74IICxx logic devices should he usedeverywhere, This allows for the omis ­sion of three 3.3 kD pull-up resistor!'> ,The original VSP com puter CPU hoardrequires the following modifications:

The pad!'> below the EPROM socketshould he connected so that pin-27receives the " 14 sil!-nal requi red hythe 27(: 256 EPRO M. Origina lly thispin is connected 10 +5V when usin gthe 27128 EPROM.

2 Th e RA~ should he Increased from64 kbytes up to 12R kbytcs . This isachieved by piggy -bac k solder ingIWO addit io nal 43256 RA M chips onlop of the e xivting IWo RA M chipson the CPU board . /\ 11 pins of theadditiona l RAM chips are connectedin parallel with the existing RAMchi p pins, except for pin-20 (chipselect). The IW I) chip-select pins ofthe additional RAM chips arc thenwired 10 pin-ll (Q4) of the middle74JIC138 address decoder.

153

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VHF COMMUNICATIONS 3/95

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VHF COMMUNICATIONS 3/95

F'i~.48 : GPS/GLONASS CPU. upper side (lop "jew)

3 An HSCH I00 1 Schottky diodeshould be conn ected between pin-l I(<")4) of the tor 74Hf:13 S addressdecoder and 'h e DTI\C K signa l(pirJ-12 of the 74IIC05), to acknowl­edge the additional RI\M chips 10

the CPU.

The keyboard connection remains un­changed. Th e total /partial reset switchhas a new function with the GPS orGI,ONI\SS software. In the case of astand-alone porta ble receiver this inputshould al~ay~ be left open (+5V)!

The parallel output port (PD71055channel-B) is now used to comm andthe HD44780 LCD controller. Sincethere are only S output bits available,the HD44780 is driven in the 4-bitmode - write only. The real-time clockchip PD4990 is required by the GPS or

156

GI,ONASS softwa re and must remainin place. The IN'I7 jumper must remainin place for keyboard Interrupt requestswhile the INTI jumper is no longerneeded, although il may left in place.

The printed circuit hoard is not modi­lied, as shown in Hg.~.48 and 49, theaddit ions and modificat ions arc fullyvisible on the component location planin Pig ..'iO. The connections of the S·keykeyboard and the LCD controller arcalso shown in Fig.50.

It i ~ recommended thai the CPU hoardi ~ tested first, if possible, in a DSPcomputer. and then modified as de­scribed above only when it is fullytested and working 100%. In parti cular,the CPU board should be tested athigher clock: freq uencies to find anydefect ive components. A 10 MIll. ver-

VHF CO MMUNICATIONS 3/95

••Fig,-l9: (; rS!G LO~ASS CPU. lower side (bou om view)

sion of the MC68010 will u_~u3 I1y worklip 10 a clock frequency of 15 Mil, OIl

room tempera ture. so a 12 MHl clockcrysta l is a safe choice. The (iPS or(i LONASS software docs not requ ire..uch a high clock frequency. till! theaccuracy of some measurements ishigher and (he updating of the displayis faster OI l higher c1IK:k rates .

-l.12 M.kry Keyboard

A portable GPSj( iLO!'lASS receiverrequires OJ small keyboard 10 issuecommands to the com puter. Since a fullASCII keyboard is impract ical for aportable piece of equipment , a smallx-kcy keyboard was developed forportable receivers.

The circuit diagram of the 8-key key-

board is shown in Fip:.5I , The 8 keysclose towards ground. otherwise theinput lines arc held high by pull-upresistors. A priority encoder (74HC I48)is used to encode the Kkeys into .3 bits.A double moncaaole (74HC45.38) isused to generate the strobe pulse after akey is depressed.

The s-kcy keyboard is assembled on asmall single-sided printed circuit boardas shown in Hg.52. This printed circuitboard was designed to fit on the frontpanel of the rec eiver and carry eightsqllarc (12 x 12.7mm) push-buttons.The location of the components isshown in H p:.5J . Due to the spaceconstraints all of the componentsshould have a low profile and smal ldime nsions. The capacitors have a2.5mm pin sJ"'3cin l and the resistors are

157

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FiR50: GPS/GLONASS CPU. Component Ov~r18Y

01nt00

(;NO

8 _ 10k

t,OO" LI ,,0< r -•~e-

I 74HC4')18l' «." r ,.,

•~ " n"!. ,

" Q (

"rt:. ,--_ . , , ,

"• ,t-' n • "I T

"n , '

" I) u,

r ,11 ;1 " Qih"" Ii 0lf1-,10 I ~ ii"i' .

" ""l' r S5 l MV

...".­>--s(~>--s('s(>--sI'~>--s(

FI~.51 : C1rcuil orthe S. li:ey Keyboard

158

VHF CO MMUNICATIONS 3/95

Fi~.52 :

g-key KeyboardPCB (bot tom view)

installed horizontally . The 8 x 10 kOresistor network in a SIT , packageshould be first soldered in place andthen bent towards the circuit boardTh efi-pin connector is installed on the back- so lder side of the hoard!

The GPS/GLONASS receiver softwareonly accepts ASCII characters from $30to $37 as commands, corresponding tonumerals 0 to 7. These can be gener­atcd by a standard ASCII keyhoardwith a parallel output. or by suitablywir ing the 8-key keyboard described. Inparticular. to obtain the codes between$30 and $37. the outputs DO. Dl andD2 should be wired to the correspond.ing inputs on the CPU board. Inaddition. D3, D6 and D7 should heconnected to ground and D4 and DS to+5V. All these connect ions, includingthe supply rails and the strobe signal,were already shown in Fig.5O.

4.13 LCD Displ"y Module

The only practical for a portable GPS/GLONASS receiver is an LCD modul ewith built-in drivers. Such modules arcavailable in many different shapes and

sizes, and mayor may not he equippedwith a display controller. LCD moduleswith a built-in contro ller are easy tousc, since the interfacing to any micro­procesw r is very simple, it is identica lto a parallel I/O port.

Most small dot-matrix alphanumericLCD modules use the Hitachi HD44780LCD controller. This integrated circuithas an on-board, extend ed ASCn char­acter generator, a display area RAMinclud ing up to two rows of 40 charac­ters eac h and all of the liming circuitsrequired to drive the LCD. Modulesu~jn~ the 11044780 controlle r may havea different number of characters perrow, or rows displayed. the totalnumber of characters is, however, lim­ited hy the internal RAM to RO. Sincethe HD44780 SMD flat package hasonly RO pins. addit ional l .Cl r driverchips (lID44 ICX) are used in most LCDmodu les.

AN LCD module with two lines of 40ASCII charact ers each was selected forthis project. Such an LCD moduleincludes the liquid crystal display itself,one HD44780 LCD cont roller and fourlI D44100 LCD drivers. Further. the

3» rr ~3(lH Is, / " I" /'0~ ~ mHm ~.

~ ... e.... .. ;::; . /;7 / S", I;, I;,L!.. 1 :r: «>

55 l MV

"' iJ!:.~3:

X-key KeyboardComponentOvertey

159

VHF COMMUN ICATIONS 3/95(j- ------- - - ----"-"-"-""""""""''''''''''''''''''

...12V120~

, 470~

" ] •OUT

III TRIG 2 10kTRE 6

S53MVOND

9/2NV1

liOOn 1.2W

r---->.-- 0UT1

I EL suppl y

220p'--4_ _ oun

Fig.::i4: LCD Raeklight Power Supply

MSB data

LSB data , 4-hit nus

5S3MV

I 9V I_-_ uwnov I

-ir,20p -l~ ,o p

Ground+5V supplyLCD vo ltage. wiper oftile contrast potRegister Select,o= instruc tion, I = dataRead/Write, () = write,1 = readEnable, 0 = inactive,1 = act iveLSB data , x-hit bus

Pin-l Vssl'io-2 VddPln-J Vo

Pin -4 RS

Pin -5 RfW

Pin-6 E

Pin -7 D130Pin-R DBlPin -9 Dfi2Pin -IO DnJPin-II DB4Pin -l2 DB5Pin-I) DB6Pin -14 DB?

display module may include some formof illuminating the LCD, either EL foilor LED. The tarter is recommended ifthe GPS /GLONASS receiv er is to beused at night as well .

Alth ough such display modules areavailable from severa l different manu­fac turcrs, tile print ed circuit boards onwhich they arc mounted all have thesame dimensions: IR2mm wide x 33.5high x 1.1mm thick and all have thesame 14-pin electrical connector. Thepin numbers are usually marked on theprinted circ uit board and the pin alloca­tions arc as follows :

Fig.55: LCn Backlight Power SupplyPCB (bottom view)

Fig56: LCD Backlight Power SupplyComponent Overlay

160

VHFCOMMUNICATIONS 3/95=-======""-------------(~

1NIB1

C' SV

<CMOS

1k1

. <_ NjCd,- :=::: 3.6V

-I 60mAh

3k3 1k5

; vv' 100IlH

100 H

" '4~'f1N 5S1S

1n 51,11

....c"":'.. 3k3

trc21S S2D

1N414S

B013S

680

BCllS~-If.j'f-D-.-jS5 3MV

<121,1

1N4001

L __~~~_ 81,12

6k61--,-- - '" pEn

1k2 /1::~B(~ aa

1k2 238 47k

F ig.57: Power Supply and Reset Circuit

The EL or LED back-light may havetwo additional pins on the connector orsolder pads on the printed circuit board.

When LCDs are driven in time multi­ple x the adjustment of the voltageapplied to the I .CD is crit ical to obtaina good contr ast. A con trast controlpotentiometer is usually provided toadjust the nest available contrast for agiven viewing angle . Thi s potcntiom­ctcr provides the Yo voltage to theLCD module . Modem LCD modulesrequire operating voltages of less than:'iV, so the resistor termi nals ca n beconveniently connected to ground andto +5 Y, whilst the wiper is connectedto U1e V o input.

Due to the inte rna l circuits o f the LCDcontroller and driver chips, the internalI.CD ground is vee (+5V). The volta geacross the LC D equals the potenti aldi fference between Ydd and vo. Thecurrent thro ugh the Yo te rmin al Is verysmall. so a 10 kG linear potentiomete r

is suffic ient for the LC D contrastcontrol.

If usin g an LCD module with an ELfoil hack -light, a sui table power supplyneed s to he built. The J::L foil usuallyrequires a suppl y voltage o f approxi­mate ly 1I 0 Y at around 500 lI/" Th(~ ELfoil behaves electrically as a lossycapacitor. T he vo ltage across its tcrmi­nals affects the amount of light pro ­duc ed, whil st the frequency affe cts theCOIOllf o f the light.

Fig.58: Power Supply and Rese t PCB(bottom view)

161

VHFCOMMUNICATIONS 3/95(~ -----------'-"'--"""'===~

,,-: -

Fi~59:

Power Supp ly andRN:l CtreuuComponent O"crlay

,

, f--,

( PU· lloord D~ P . 1' l atL ll ~

tcbee l ( uoh>n) ~

~

ro

55lMV

I LCD Macli,.., Ifronlplatt.,. ~ Slr tnl- A~""I'.."'"

I h .. - tcs tcto- I \;;J U LJ, l~oto

StrO lflwors

fu r U O· Slromv~sorgun9

• '6~( l'u{ htunll und RESET

G"" HF. Tfl l• GPS< ZF +Tell, 0~ ~N.N>

An..,( ht von untl'n

Fil!_60:Portable (IPS Receiver:\1odlllt" Location

162

VHF COMMUN ICATIONS 3/95

A suitab le power supply is shown inFig.54 and includes a power oscillator(555), a step-up transformer and a fewEMI filtering components. For 500 Hzoperation a conventional mains trans­former with a laminated core can beused, either 220V19V or 220V/6V, ofcourse with the primary and secondarywindings interchanged . A 1.2W or

Oraufs i(h t

GLO NASSLoqik

,, ,, ,Synt hesizer :(untpnl I,,,

'---+- - - --~

,-- - 1-- --,,Stromvers rgung Iund RES T :l unten ) I,

1 LCD Module

fr ontplc tte

rcu -e ccro(ob ~n l

OSP - P(llhne(un ten I

-

U Strom - A~nnen v ers~ I I

I BN - Toslll tur

Stromversf ur LCO ­Be(euchlung

"•,'2

" "N".­N>

GlONASS Pll ­Synt hesizer

Gl ON ASSZF - Teil

Abs(hlrmung

GLON ASSZF - 'lail

Fig.61:Portable GLONASSReceiver ModuleLocation

163

the load. Since the osc illator feedbackis taken from the output (pi n-1 of the5:~5 ) , some 555 IC:s may not operate ina stable way in this circuit. In the latterease the solut ion is to increase theoscillator frequency hy decreas ing the100nF capacitor.

Of course, an LED back-light is mucheasier to me and usually only requires a5C DC supply.

VHF COMMUNICAn ONS 3i95

01.101 Power Sup ply e nd ResetC irc uit

The GI'S/G I ,O~ASS rece iver is in­tend ed to be operated from a 12Vbattery, with the negative grounded.This supply Voltage is common 10 allportable and mobile equipment.

The ana logue circuits of the rece iverarc already designed 10 operate from a

_ .MENU KEYS . DISPLAY FUNCT ION

KEY # 4 KEY # 5 KEY # 6 KEY # 7

lCODE $ ~" J (CODE $ 35) (CODE S 35, rccoe S 37;

SHOW ax S"O\'/ SHOVi ""cUiMENU , CHANNEl 1"''''EUIATf A" . HAGfU su -cs-

OATA NA ~ DAI A "'A~ o"' ~ " '.."""A·~

o\CT10t<SHOW I ~X S"U\'/ SI<O-' S"Q l i

AF TERCHANNf l . , l MMf DIH E A~rnAGED ::;,., r AA.

FIRSTDAH NA ~ OATA 'JA'i O~ T . S ]A -cs

PRE SSI'Ia

ACTI ON ' 'I CRto Mf~ I'"" IAFTE R Ill( CHANNH ' 0 vo ' .. '0011:1. <REPEAH O NUMBI' A ACTION A C 1 I C ~ , r r l L IT ~ ;

PRESSING { ", 3 , ~ 1,2 , A. VA' . AC

<, /' /' , I .:/

sr- A" L

'" Of c Rf ""ENT CL ~ A ~ ~x C ·IAM'~ I s

" CKAN"n' 0 A', f PAc,,, :I , o ~ " . · c ", · , .

( ;~f ) PR" . 'C H" ._CTlOt< 0"-_ A" :; I" . < ~CV

A" "'AI.;A::

00s et LC" ' ''''~> '" ': -'. ' EO!1'

W .. INC~ E Mf "'T W Ol,l.(;I.jA'IN!:L c s c er f S, V'NV f ~ S'SECOt.OS

~ ( CODE) PA". iCHN.C~ ': S ~)v:n

s aU'SPLAY FO~ "' AT

P'E;, I ' VE; '

I -WI- «ev DECREMENt SH LOti "......•

sr - V A"W " CHANNEL IF

DEGAEESiDECIMA.. FRACTIONS"'-ELLITE

~ (CODE ) S E LE C ~

< ' " 11 ' Hz STEPSIOISPl./l.Y <OA"' AT

~' C [)E

[

1 m INCFlEMENT SET XiV SEt evr o

" CKANNEL IF SATELliTE

( ;~F )GAUSS ~ 'l :)GE 'l

SELfC~

( f .Hz STepS! DISPLAY FORMA~ IoIODE

164

wez«Io>­«~

(fj

II-

eZZ[«(>';••62,~ GPS/GLO!'OASS

Receive r Status

+12VC supply rail , since thi s voltagerepresent s a convenient choice .

Of course, digita l circuits req uire a +5Vsupply voltage, but bes ides the +5Vthere are other requirements. A GPS orGJD NASS receiver should include areal- time clock that operates even whenthe receiver is powered down . Simi­larly, the almanac data including infor ­mation about the available satelliteorbits should he stored in the compute rmemory when the receiver is powereddown.

Finally , since the +SV power drainam ounts to about one hal f o f the totalpower drain of a C;!.lS or GLONASSreceiver , the +5V supply re gul atorshould also have a good effici ency,especially in a portable receiver .

The requirements for the mic roco m­puter power suppl y are therefore thesam e as for the DSP computer pub­lished in l1J and l2 1. The original DSPcomputer power supp ly is howeverabout 10 times too large for thisappl icati on. so a scaled-down version isshown in Fig.57. The latt er includes aswit ching regulator from 12V to 5V, amemory (clod) backup batt ery and avery rel iable RES ET circuit.

The microcom puter pQlVer snpply isbuilt on a single-sided prin ted circuithoard as shown in f ig5?; . The corre­spo nd ing component location overlay isshewn in fig.59 . Ail of the resistors,diodes and chokes arc insta lled hori ­zonta lly . All of the capacitors have aSmm pin lead spa cing.

Several mounting holes and relatedpads are provided for different styleNiCad batt er ies.

4.15 (, PS/GLO NASS receiverModule L oc al inn

A (iPS or (jI.ONJ\ SS rec eiv er includesborh low-level Rf signal arnplif k-ationand processin g and very nois y di~dtal

ci rcuits. so the module location has tobe selected carefully and some shield­ing is required in any r use.

In the case of a (iPS or CiLON AS S

receiver operating as a peri pheral forthe DSP computer, the Rf part o f thereceiver shou ld be built in its ownenclosure, whi le the dedicated DS!'hardware module is plugged into thecom puter bus. Of co ur se, it is assumedthat the computer already has its ownshield ed enclo sure.

The GPS receiver Rf unit needs noadd itional internal shields among thethr ee modules: RF, IF converter and 1l­amplifier. The GLONASS receiver RF

165

VHF COMM UNICATIONS 3i95(~ ------------'-'-"-'~"""'''''-'-'''''''''-'''''''

unit is more rornpliru tcd and rcquircv.~OIll C shielding . i ll particular. the ( ;1.0 ·Ni\ SS 1'1.1. synthcciscr log it, needs 10

be wel l shie lded from the rema iningmod ules: RF. IF co nverter. IF amplifiera nd 1'1.1 . convener.

In t il t' ca cc o f a stand-a tone porta blec;flS or (iI.O NASS rccc i..-cr it is ofcrutrs c' dcvirable (0 ha ve th e com pleterece iver packa ged in one single cnclo­sure . It i.~ suggested that th is encl osureid fabrica ted from unpainted aluminiumshee t to have a good electrica l cont actamong the various parts. Such a con .lain cr is made o f a rect angular frameand two ( 'OVI,.'rs installed with wlf­locld ng S(' f l' WS .

The (ram " has an addit iona l inte rna lpla te that div ides 11K' inte rna l volumeinto two sections, shielded beth fromthe outside and each other. One of nrcsect ions is used for the noisy digit;l!circui ts and the other lor the low-levelRr stages .

Non-I nterfering modules, such as thekeyboard and the power supplies, mayhe install ed in e ither sect ion.

TIK' s ll1!gr st ~'d modu le locat ion for il

portable (i PS rece iver is shown infig.60, The suggested dimensions arc2rXlmm wide x ]oommdeep x 80m mhigh,

T he interna l plate is insta lled at aheight o f 30mm, so that the digitalsect ion has a volume of 200m m x160mm x 50mm (top) and the analoguesection a volume o f 200mm x 160mm x30mm (bottom), The internal plate tsscrewed onto the frame on all foursides with many screws to ensure agood elect rical shielding.

The two modules with (14-pin liurrx-atdcon nec tors arc insla lk d on :1 .\ 11011 husmother board with juct two fem ale con ­ncct ors with the correspon ding pins tiedtogether. The hns can he made hy" ull ing a piece o f the DSI' com puterbus hoard. or hy "imply i n sl ;l lh n l~ twoconnectors on a piece o f a univ ersa lhoa rd with hole s in a uniform 0 .1 pitch.

The connections between the anal ogueami di)!it:ll uni ts do nOI requ ireIeodtbrough capacitors if they arcrouted ca refully . away from the scnsl­t i v (' or V ( ' ry noisy com ponents. SOIllC­times it is ;11.'0 o f b enefit to addiuonall yground the coaxial cable sbic klv whencrossing the internal scree n.

Th e suggested module 1IIl'31ion (or aporta ble (TJ -ONi\ SS receiv er is .•hewnin Fi!!.6 1. T he sugpcstcd dimensionsare 24(hnm wide x ]60mlll deep xxnmm high.

Th e internal p late is insta lled at aheight of 30mrn, so that the digi ta lsection has a vo lume o f 240rn m x160rnm x 50rnm (top) and the analo~lI e

section 240mm x )(j()mm x 10lllm(bouom). As with ti ll' GPS receiv er theinternal screening plate is screwed ontothe frame on a ll four sides .

In add it ion, there is a small shie ldbetween the RF module and the re­maining module, in the analogue S~T ­

t ion . On the other hand, in the (TI.O­NASS receiver Ihe computer po wersupply is installe d in the digita l section,toget her with the PLL synthcsisc r logic.

A list of PCBs and kia for this projectcan hi' found on page-l v t of this issue

(References for this projec t can hefound overl eaf)

166

VHF COMMUNICATIONS 3/95

7.REFERENCES

[I) Matjaz Vidma r: "Oip: ilal Si!'nalProcess ing Techniques for Rad ioAmateurs , Pan -:!: Design of a nspCompute r for Radio AmateurApplicaliom";VHf Commu nications 1/9 1.pp 2-24

121 Matjaz Vidmar: ~t)jJ! i la l SignatPr rcc....in!! Techniques fOT RadioAmateurs. Part -S: Construc tion anduse of the nspCo mpute r";VflF Communications 2/Hf) ,fir 74 .94

131 Jonathan S. Ahd. James W.Chat fcc : "Ex iste nce andUniqueness o f CPS Solut ions";ra pes 952-9SfJlf)-9 I , Vol. 27 IEEET ram. o n Aerospace andElectronic Systems

(4) "Interface Control Docu mentMII0 8.f lOfIU2-4{)fI. rov-E". (84pages). Aup:U<;f 7th. 1975.Rod.well Internationa l Co rpora­lion. Space Division. 12214La kewood Bo ulevard. Downey .California 90241. liSA

151 "lmerrecc L'omro l DocumentGl'S-2 IJO", (102 pa~e~) , I\uj!u~t

71h, 1975,Roc kwel l Internat ional Co rpora­lion, Space O pcra tiom andSate llite Systems Div ision, 12214Lakewood Boulevard, Do wney,Californ ia 9024 1. lJSA

16J ~( ; I oha l Satel lite Navigat ionSystem ( if .O NI\ SS InterfaceContro l D ocument" (46 pages).

191UI. Research-and-Product ionAs~iation of Applied mechanics,Institute of Space DeviceEngineering. GI.nkmnux , Russ ia

(7] Robert C. Oixon: "SpreadSpec1J1Jm SYQcms", (4 22 pages),1984, Second Edition, John Wiley& Sons, New Yori:, USA

181 Malj:17. Vidmar: "(li ll.iu l SignalProcessmg Techniques for RadioAmateurs, 'Ih coreucal Part ";VI Tf Com munications 2/88pp 76-97

[9] P. Mattos: "(i lohal Pos itio ning bySate llite", (16 pages ), lnmos.Tec hnica l note 6.5, July 1989

IIOJ J. D. Thomas: "funct iona lDescriptio n o f Sif!: na l Processing inthe Rogue UPS Receiver". (49pages), June I, 1988, JetPropulsion Labora tory , Ca liforn ialnstirurc o f Tec hnology. Pasadena,Ca lifornia, USA

1111 Chou b C. Kilgus: "Sha f'l.-'\IConica l Radiat ion Pattern of theBackfire Quadrifitar Helix ", (page."391·397), IEEE Tra nsactions onAntenna.. and Propagatio n, May 75

(121 Matj;u: Vid mar. "II. Very LowNoise Amplifier for the I.-nand ";VIIF Communica tions 2/92pp 90-%

(13] M3tja/. Vidmar: "Rad io Ama teu rApplications o f G PSKiI .ONI\SSSa telli tes: Using GI'S,K;LONASSSa te llites as an AccurateFrequency / Time Standa rd";(pages 186· 190). Scriptum del'vonraege, 37 We inhe imer UKWTagung , 19/20 Se ptember 1992

167

VHF COM MUNICAn ONS 3i95(~ ---------_.:!-""-"""===~

Dirl.-lnR V,.",./ Burchard, Box U .Jlfi. i'..'airohi, Kenya

Linear Signal RectificationPart-l

Linea r r cr li nClll ioll is present if theIlC out put sig nlll from a ci rc uit[l nsta ntnncous or mea n va lue} is pro ­portlonul In the AC inp ut !'OigOlt l for111(' same circ uit (insl a nln n('o us. pl'lIl...R:\IS. or 111('an value). In tech nica llyrealised syslrm, we must 8.....11111(' ancrror in the prnporlionHlilY. i.e. auepertnee fro m ideal ('on\"t' rsio n.Should t his lie in the orde r of HP­pro, imaltl y I -:f> , men thai i.. sum·ej(onl for point er type ino;lrumenl ...st r ip chart recorders or oscillO'iC'opes.Fo r d i~ i l al d ispht ~iS a nd fu rth erproc~"ing. R hiaher deeree of 8C('U­racy i.. required - 0.1 or, i.. d ~inlhl('.

a nd ('\'(' 0 grl'lt trr pr('d,ion woutd beh ('I1 ('1'" •

Some improvement in the charactcris­tin can he obtained by mi n)!. activ ecompo nents. It is sometimes even po~ .

siblc to manage cnure ty without diodes.as Pan-z will show,

Finally, Part III will dea l with external­ly-coerrolled rect ifiers which, toy theirvcr)' natures, :lTC linear even in thevicinity of the .tero point. No aucmpr i~

made to ccal with any o f tbesc topic~ ina compre hensive fashion, The idca ismore to illustrate the linds of circuitswhich have proved them ..elves in day­to-day practice without the need forexplaining 10n1'- mat hema tica l derive­tion procc......es to clarify how theyfunction . /\ n oscillog ram will malething... d earer where nl'l'e~~:lry .

FORI':WORIl I.I:>lTR(] J) ucrt(]:>I

The .~ i mplc ~ l signal rectifier i, thesemi-conductor diode . Part I will be

conce rned with irs character ist ics andwith those of rectifier circuit... which.apart from diodes, contain only pacstvccomponents,

168

Signa l rectification compri ...cs the mea... ·urem ent of /\C voltage and demodula­tion of 1\\1 and ~~1. the latter with arefe rence tuned ampli fier circui t being

VHF COMMUNICATIONS 3/95

needed. So a modulat ion measuringdevice comprises two rectifiers. one fordemodulation and a second one tomeasure modula tion. The frequencyranges of radio-frequency carriers andmodulations intersect. 10 kil l. can heeither the carrier frequency in a VLFsystem or else a modu lation audio­frequency, 4 MHz a data strea m cycleor else the carrier for a short wavetransm itter.

So rectifiers may therefore be involvedwith frequencies from 10 l lz toto Gl lz. II could scarcely he expectedthat this wide frequency range could behand led by a single type of recti fier ordemodulator.

Rectifiers which work with ch argingcapacitors, i.c. which weight mean.RMS or peak values, arc suitable fordemo dulation only if there is a fre­quency gap between the ca rrier fre­quency and the highest mudulutionfrequency. Those which convert instan­taneous values do not require thesegaps.

For the sate of completeness. it shouldbe poi nted out that d i ~il al signalprocessing does not need a frequencygap either. But it is not the subject ofthis article.

The mathematical treatment of rcctifi­ers leads to non-linear equations and is

difficult. So I will attempt 10 get bywithout using any mathematics at all.

2.PRECISION

Only a low degree of preci sion isrequired for the acoustic reproductionof a modulation, Slope deviations of ±10% produce no audible differences,ami eve n small non-Iincarities remaininaudible.

PAM-demodulation is even less critica l.Everything abo ve the noise level is"mark", the rest is "space". Great e rprecision is needed for measurements.For historical reasons, and becau sepointer meters used to have friction, anerror is given :I S a percentage of the fullscale deflecti on ,

This makes sense, even with digitaldisplays. So I d ip- it is sti ll a specificpcrcc ruogc o f the li nal value dispiaycd.The display can be no more prec isethan this per centage , and the rect ifierneed be uo more precise than this.

An a('('llJacy of I % is rea sonable forthe analogue pointer instrument. Forthe usual 3 1/3 character digital disp lay,an error of ± 0,1% is hctter than theaccuracy for most commercially manu­facturcd products.

169

F ig. l :Measu rement nl'cllil COl' leslingDiodes lIsin2 varfous I..cadRes istors. I)reieek =A; 1.11

tc stend e Hinde =J) ilxl e under test :T as! kopf =probe

Ils.rillcskcpel U tesrence mcoe

O r e l e{ ~ t vss :-t:+-' 100.1 _~~~"""'-,30Hz. 1 TQstk opf I

~~ ~M.O

~---I'----'-~'"--J

VHF COMMUNICA n ONS Ji9S

Equipment whic h is subject 10 consid ­crablc KIl·~al in)! must have somewhatteucr rectifiers. II is 31.-.0 true here Ihalthe aC'CUTaC)' o f mcasuremere increasesthe elo...cr you remain to an a\lerapetemperature o f 23° C.

l .ii.,\· all wnu t·Hud u\"l.lIS. t lk' d i.",k i ~

1 ~' I1l p"· r :l ll l rl· ' llq....nJ,·n1. '11Il' T( ' nf Il1l'forward dlt 'r \ n lla)!~' amomuv 10~Ill V/K" im-..pccnvc of the \lo ltal!..·. andrbat IIf 11K' IIff·04ale curre nt dou hk ..l ·vc·ry II K, In Ilk.' quad ratic range. 111\'corwcrvion erro r i, (J.]'k2! K ark.!

becomes rar i..t l)' smaller in IOC !inl"ar

r3n~c .

E X3t' l mcasurcmcurv. or very preci semea surements. r an not he taken di­rccuy in a snowstorm. or ar midda ywith the ~1 1Il vertically overhead. in theopt'n :lir. If WI,.' take into account thecom fort and IhI: arnl ily 10 think of Ihl,.·p:rsun making the measure ment . anambient tempe rature range o f 18 1028° C i .. full y aJ..-qll.1t t' for mea sure­mcnt equipment . withm this tempera­ture range, rh..• quadratic diode rect ifieralready rc3d"'li prcci... ion propc rtic ... . allthe more the linear recti fier docs.

\~ -------------""-==="'-"'=~

.. ,

1:"1'1.1 'E:"( 'E OF TD II'E1{'\·n ;RE

4.FREQ UENCY COVERAGE

It is in no way advantageous if aninurumc nt has a wider frequency rangethan il 1Jl.-N\ to have 10 sun the

FIJ.:.2: Screen ImHJ.:c~ tor 'I't's1inJl: urIN4148 (8). BA481 (h I andA A1.18 (c)Y: O.2V/di¥ X: !'m~d l¥

The fieurcs on t he lint'S refer10 .he nurntM' rt'd "" lIchpoo;.ilions in t·~. 1

170

e ~ •I'I-~

N

UDV

Burchard

F ilZ"3:v onage-Curre nt

." +---!- +--L-Ih lV1l-1 Cba rac ter tsticsIor Diod es tested•usin2, a I~ Sea le

,',

• -t

. 'EI"

,,'-0.10

,',.J ,..

requirement s. The wise limitation o f"no more: than necessary" prevents thelow-frequency voltmeter from cont inu­ou~ ly measuring the nearby medium­wave transmitter as well, or Ihc powermonitor ci rcuit from hcinl! influencedhy the s i~nills from a ripple contro lsystem . It is admittedly nor alwayssimple to design the useful frequencylOJnF:e without damping and everythingelse with 3 <; hij!h 3 damping as posst­hie. Depending on the frequency range.act ive, l .C or coax ial filters may hcnecessary. However. one thing is OI l·ways possible and should never beforgotten - the capaci tor at the rectifierinput, which prevents DC sil!na ls frombeing inadvertently included in themeasurements . Many mulnmeters donot have one. which often makesnonsense of the user's measurements.

5.0I0IlK';

Three types were sclecn-d from themultit ude of commerci ally ava ilablediodes - a germanium point diode, asilicon Scbou ky and a silicon junctiondiode" They can procc.... approx imatelythe same current levels and have sim i­lar dep iction junction capacitances. Ifwe investigate their rect ifier character­isucs in a circuit a.. per HIt.I . then weobtain very di fferent results. as shownin Fig.2. There should be 4 curves oneac h individual illustration . •There arcusually only 3. cxecpe for the conduct­ing stale region in illuwretion (a) .Depend ing on the load rcs i..tor. thevo ltage drop tbcrc goes from minima lto considerable (411 to 40UmV). The

171

VHF CO MMUNICATIONS 3195(~ - ----- - - - ----""-""= = """"""-==

., .,~ - \

",,.-1

,,,,_--,__1,

l) ' 1 1--- -1- - 1

Fi~"' :

Se ml- Loa a r n bmfe rep rewnlnlionof Fo rwa r d Cha r Ht"lerb tic s

I d isplays more dcfall-,''--_---=-J

i ,-j1-+ - ·

-~ha-;:;j-

- -+i=CT

•,..

reverse current is not low enough forthe highest load resistor. For the highes tload resistor in illustration (h). it i.. 110

IOTlF-cr possihle 10 detect any rectifiere ffect at all . with a load of I Mohm or10 l o. the voltage drop is )00 or2.,;nmV. Finally, in illustration e, wearc de aling with a directiv ity which is

adequate only for the smallest loadresistor - the voltage drop is 120mV.Nonc or the three diodes come.. any­where ncar being an jckal recti f ier.'lbey arc not ideal conductors ill theconduct ing sta te reg ion and they do notprovide an ideal tJlod : in the reversestate.

FIJ,l.S: ( ;cncnd Conversion Charactcrlstlc or a Fig.6:Rectifier (a), and the n arre r Seliling anda vnidant't" orBreakd own R~ion (b). Fur therclariflca tlo n in text .AusJ,: ·G ro l1e = O utput val ueSr.: alcncndwer f = Full-scale va lueElng-Grone = Input va lue

Simp le ReclinerMod e l rorc()n~ld t'rin~

Dtmenstomng

' 72

If we plot the voltage-current character­istics of the diodes, then we may obtaina picture something like Pig.J . Here awide linear range is clearly apparent inthe vicinity of the zero point. The diodeis best described as an ohmic resist­ance: 100 kO for the AAZ1 8, 3 MO forthe BA481 and 100 MQ for theIN4148. However. in realit y a slightbend in the curves is present. Thisrelates to the quadratic range between ­2 lJT and + 2 . lJT• about which youcan read more in Burcha rd (I ). Withthe coarse sca le used here, this can Hotbe seen . In the reverse region this isfollowed by a more or less pronouncedplateau wher e the reverse current islargely constant. In the vicinity of thespecified breakdown voltage, the re­ve rse curr enr then rises sharply. It isthis area of rapid change which dis­pla ys the biggest variations betweenindividual diodes of the same type andalso betwee n di ode types produce d bythe same technology.

In the conducting region, the gradient svery quickly become sharper abo ve 2 .UT. You have to me a semi-logarithmic

representation, as in Fig .a, to recognisethe diffe rences more easily. Here thecurves initially run parallel at intervalsof 2 current decades each, to bendround into the horizontal above variousindividual current levels. The bulkresistan ce becomes noticeabl e here . Itis clearl y at its lowest for BA841 and atits highest for IN4148 . Apart from this ,anyone curve can be obtained from theothers by a hori zontal shift of approxi­mately 150 mv.In the zero point region, the curveintervals were 1.5 current decades andthe plateaus for the reverse currentswere only about I current decade fromeach other. It can he concluded fromthis that the rectifier quality - the ratioof the conducting curr ent to the block­ing ('III1'ent - is 10 times greater in theex ponential characteristic range for ger­manium than for the Schottky diodeand IOO times greater than for the Sidiode . This observati on app lies to theindividual diodes measured here. Withthe multitude of types on offer. and ifwe take into account that . for example.Schott ky diodes arc manufactured for a

Fig. 7:Various types of Noisewhich can be cor rectlymeasured ustmg theQII8si-RMS Value RcclificrYi: White Noise with

Normal Dist ri huti onY2: Band Pass Noise, Q =IO

Rayleigh Dtst rfbuttonY3: Band Pass Noise, Q=1

Mixed DistributionX; 5ms/divCentre Frequency of BandPa sses 1 kHz

173

@

VHF COM MUNICATIONS 3195

C R1 R2

::-"""? ,;.(, - --4-1~

@Fig .S: Genera l Rcctlrler Cir cuit for nil four types of evalua tion with Floa ting

Load (8) . Hod It Common Line from Input and O utput (h). which mayalso he ea r thed

very wide 41 ran ge. in an individualcase a Si diode can also chance 10 havea higher rec tifier qua lity tha n a Gcd iode. In addition 10 this, ancnt ionshou ld also he paid to the capacity .reverse recovery time and series induc t­ance if you arc dealing with higherfrequencies.

6.CONVERSIONClIARACTERISTICS

It is very common for a rectifier todisplay a relationship bet ween inputsand outputs like that shown in l-ig.Sa.Range I can be explained by the areawith quadratic recti fication, and RangeIII by the influence of the blockingcurrent as a breakdown approaches.Because of the high manufact uringto leranc es in the blocki ng state region,

a sufficient ma rgin must he preservedso that there is no breakdown - i.c. thereadings must stay within linear rangeII. If we now scale in such a way tha t

the desired output values (c.g. l OOmA)are set for the desired input values (c.g.5V), then we obtain a l 'UTVl' line like(h), Only half of the original error band± f is now in m e, The solid curv eapplies if it is desired to retain the zeropo int simu ltaneously - the conversionl ' ITOr is always negative, T he dolledcurve is present if the zero point ismoved forward. which can he donewith a pointer instrum ent by usin g thezero adjusting screw, or else can hebrought about by giving the diode ahias voltage. With skitlful design. (heconversion error above 2 . U-r can hebrought down close to zero. The proce­dure is descri bed in greater detail inBurchard ( I) .

Recti ficat ion R I R2 C

Peal Rectification 0 2.' MO §Quasi -Peal H O 2.5 MO O.2 ~

Quasi-RMS 250 Id l 1.8 M!l §Mean Value 630 kfl 0 §

§ depending on Low Frequency cut-off required

Table- t

174

VHF COMMUNICATIONS 3/9S

7.ERROR ESTIMATION

The biggest conversion errors (bothrelat ive and absolute ) occur in the areaindica ted by the arrow in Pig.Sb. Thisis where we find the input value f x endsca le value present. The output valuemust alrea dy he above zero - it isestimated to be 0.2 to 0.5 x f x fullscale value. H g.a provides informationas to the input va lues at which thiscurrent flows. These values , multipliedby l ff, give the smalle st possib lemeas urement range with the error f.

A conceptual model, as shown in Fig .6.helps in dimensioning . Let the initia linput value be a symmetrica l squarewave volta ge and the charging capaci­tor, C, not he present. Then conducting­state current flows through RL for ahalf-wave, and blocking curre nt flow sthro ugh for the other half-wave . Thedifference between the two is thecontinuous average forward current, Ir.The blocking current must remain wdlbelow f x IR. This determines RJ" for 0has already been determined by thecons iderations referred to in the previ ­ous paragraph. So we already have thedimensioning for an instantaneous ormean value rectifier. To give somefigures here - a rect ifier with a preci ­sion of 1'k . wired in front of a I (XhnAmeter. needs at least 4V with a Gediode. at least 15V with a Schott kydiode. and at least 30V with a silicondiode for the end scale value.

Peak value rectification is considered inthe mode l in Fig.c in that the charg ingcapacitor is provided and the mark-

to-space rat io of the square wavegenerator is set low, Depending on therequi rement s impo sed for the chargingtime . positive voltage will be providedfor I to 5% of the total time. Thecha rging capacitor is charged approxi­mately to this voltage. The bloc kingvoltage at the diode becomes twice ashigh and is applied for twice as long.The blocking current becomes ratherhighe r and its effect lasts longer. Theconducting-state current becomes 10010 20 x Ir- with the mark-to-space ratiopercentages referred to above. It resultsfrom all this that the smallest possiblemeasurement range using a Gc diodewill be 7V (5% case) or l3V (1% case).Much higher voltages are needed forthe other diodes. especially if evengreate r precision is aimed for.

8.FOUR TYPES OFRECTIFICATION

If the level of an AC CUITent is given.this always refers to the RMS value.unless explicitly stated otherwise. Ifsinusoida l or slightly de formed curvesarc involved. it is immateri aI whetherthe rectifier is measuring the meanvalue or the peak value. because thetwo are linked by a constant factor.This alters if the form of the curvedeparts significantly from the sine.Fortunately. this does not happen allthat often to radio amateurs. A satu­rated radio-frequency or low-frequencyamp lifier rarely occurs in operation . Toreduce the electromagnet ic environ­mental pollution or the suffering of our

175

VHF COMMUNICAl iONS 3195(/' - - - - - - --- - ---'-""-""""""""""""""""'''''''''

Fi g.9:'fain ... Voltage \1 onilor Ci rc uit

J"----c::J "I-,--N-rr- - -'.

'" I2W"'" ~

_~OOJI~

car'•• the level control should he re­duced to a convenient level. If it reallybeco mes necc.."ary . :I genuine R\1Sresponsive meter can rapidl y he coo­struc tcd mi n,: diodes which operate inthe quadratic r.U1I!C. Further reading onthis can tic found in Burchard (2). RUIthere is 3 trick circuit .....hich combinesthe mean and the pea l value in :I

somewhat linear m311Jk' r 10 ge t H:ry

dose to the R. MS value . It opera tesboth with noi se (Fig.7) , 3'i ha'i beendcmonstran..d by Pohlma nn (3). andwith main.. 1Io1l31e. where the R\lSvalue i'i decisive. for hi..tnrical reaso ns(inca ndesce nt lamp light. tube heat ing},And then. a.. well ;J'i ,hi.. qU3'ii-RMSvalue r ncacurcrncnt. there i'i 31 "0 qU3si.peal; Va lue measureme nt. which i ~

required for measuring cx tcma ! von­ages and noi ses in acco rdance withstandards .

The circuit in Fi~.8 iv suita ble for all 4types of evaluation. Without any fur­ther clenflcation. it is believable thatRI = 0 leads 10 peak value rectificationand that R2 = 0 lead.. 10 mean valuerect ification. Qua\j·R MS value rcct ifi­calion lies between the twoo but elme rto mean va lue rect ification. whereasquasi-peak value rect ifica tion ilo closerto point rect ificat ion . The capacuorvkeep IX: current away and ..tore thereading without any significant dropover at least one period of the lowe..tfrequency arising. Ch3r~ in ll and dis­charging time constan ts of 1 ami 250m..arc standardised for quasi-peak value

Fig. tO:T he 'fain, w av eform i'ibetween II !J. a nd II Sq ua reW8~'e

176

VHF COMMUNICATIONS 3/95

mcasuremer u. All this then gives usTable I for d imensioning. with a l OOVfull scale value and I<,X)mA fuli deflec­tion meter.

9.POWER MONITOR C1RCCIT

Part circ uit b. in H g.S. is advantageousif there also has to be a common linefrom the input and the output.

lt can easily be recognised that signlfi­cant AC current s are present throughthe resistor, Rl. Thc self-capac itanceand self-inductance of this resistor leadto the display's being dependent on thefrequency .

Only the peak value rect ifier with R1 =o is free from this in princip le , It isthere fore preferred for radio frequencymeasurements. A small series resist­ance. RI , is often necessary 10 dampenresonances from diode capacitance andind uctance. But you need no more than100 to 200n for this.

u,

One applicat ion of the relation ships setout above is the ci rcuit in FiIl.9 . Th e ±HXhnA measur ing instrument shows theeffective value of the supply voltage onan extended scale in the 150 to 250Vrange (this is unfortunatcly the normalrange in which Ilnctuaucns occur inNairobi, where the rated voltage is240V). The rec tifier corresponds tomeasurement fo r quasi-effective evalua ­tion, It supplies suflicient output powerto generate a re ference voltage of about8V with the low-frequency transistorwired lip as a tem perature -compensatedZ-d iode . Against this, the vari able out­put volt age of the rectifier is displayedby the meter using a bridge circ uit. ThelOl.:D trimmer adjusts the mid-scalevoltage and the 221.:0 trimmer the rateof rise.

u, u,

u. • w..IIg

U' • Uo

177

Fi~.lt :

Equalisa tion orQ uad ratic RangeIIsin~ a smallAnH lo~lle

Com pute r (8 ) andFunction Soh la incd (b)

L--' '--J I,

I I <{./'IIttl I ' , , ., '.+1I ~ "I.........-:..> I'I I'*'"' 1/ 1 fl-.1 ...- I 1/ I I ~._I

VHF COMMlJN1CAn ONS 3/95(~ -""C-""'~="""'~

Fi~. 12: Eq ual isa tio n H( QlUld Tal icRa nJ!t' usinJ.: No n·LinearFeed back

A. function generator is a ll yOIl need 10

rest a 411a<;i -RMS rectifier. In thi!>context, let us e xamine Fip. .J O. lI ere thecent ral line shows the supply vo ltagecurve form which , in spite of man ypha se -angle controls and pea k rectifi­ers. is ..till father sinusoida l in almos tall mains su pply circuits. Eve n with fargreater degrees o f de formation, it willal way" lie between delta and ~1I3re

wave form.., which are roth d isplayedat the U TIle lime. A rcct if c·r whichgive.. meier readings of I:1/..f2:I/.JJ forsquan' waves . sinc waves and deltaW3\1CS from 3 funct ion generator h 30;, anoutput value which is snfficicruly prc­cbciy proportional 10 the RMS val ue.Wilh the l-jf!.8 circuit, th is is tb c case ifRJ :R 2 is approximately 1:7.

III.LlNEAR ISATION O FQ UAIJRATIC RANGE

Even for an accuracy o f only I'k, alinear rect if ier for a ll types o f cvalua­tion needs rathe r a high input votragc ,With the introduct ion of semi-co nduc­ton into amp lifier technology. the sig-

ual k"d" have lalh-n llla'l wa lly - inth..' same r.u io as th..- npl:ralinr vo lt­;) !! l ' ''. from S..-vcrul hundr c..1 Volts toon ly a (CW. It is lhus fr..'qllcnlly nu l at311 f't>"i hk to mal ..• _m l" fiC' i"'1I1 inpulvoltag e available 10 the rectifi er. " .... i....­ance can he prov ided by active rccr jfi­ere (see Pall II) and hy correcting rhcdistort ion of the quadratic IOUl!!e.

Fill-, l la shows the relevant ctrc uu. 11consists of an analogue l'l lmput i n~

module for multiplicat ion and d ivision,a com parator and an operational ampli­fier. They are wired together in such away thai the roo ts o f input vo ltagesbelow Il k are calculated. but thoseabove {H; are reproduced linearly. Sothe transfer function is as shown byHg.tlb. Natura lly. the kink in thefuncti on creates a problem. because itis not availabl e from the rectifier. Toremedy this. the comparator nmst bereplaced hy a diffeJl'nti al amplifier o fappropriate amplification, the S-fomltrans fer function of which then givesthe c oned line in HF- .II h, TIll' authorwill he happy to Five lklai ls o f thi sre lativel y complex circuit . nut there isa .... i11 simpler way, as \ hnwll hy Fif!..I:!:.

llcrc the feedback which uctcrmmcsIh..' am plification is made non -linear." sin!! the same diolks which arc 11I­l'al ~'d on the len in the radio frequencyrectifier. For very Sn13 11 rectified volt­eges. the amplification i_s inilia lly great.11 decreases continually as the rectifiedvoltage increases. The decrease in. theamplificauon is in no way hype rbolic.as it reall y should have been. hut israther an exponentia l funct ion. Neve r­thclcss, quire good lincarisarion is ob­tai ned down to a rad io freq uency

178

VHF COMMUNICATIONS 3/95

voltage of 10 mv. To avoid latch-up,an amplifier is used which can workr igtu down to the negative rail, and thisrail is then set to zero. The circu it israpid enough for wobbling and deliv ersa voltage which is equal 10 the peak­to-peak of the radio -frequency voltage.

11 .SUM MA RY

Rectifiers wuh semi-conductor diodesarc linear at sufficie ntly high signa lvoltages. They arc distinguished by ahigh frequency coverage. which is rc­srrictcd only by the characteristics ofthe diod es. Accuracy levels above 1%are difficult to obtain. At such levels ofaccuracy, the quadra tic range can be hya simp le circ uit at low signa l vo ltages.but this still means a measurement ofthe RMS va lue.

12.LIT ER ATU RI':

(I ) D'Bu rchard (199 1):Basics of Rec tifying small l\CVoltages with SemiconductorDiodesVI IF Communications 3/1991.pp. 168 -174

(2) D.13urchard (1991) :Abso lute Calibration of a NoiseSourceVHF Communications 2/1992.pp. 76-89

(J) W.Pohlma r m(1964):Rauschgcncrat orcn und ihrcAnwcndung in de r HF- eundNl--Technik.Handbnch furHochtrequenz- und Elcktro­Tcchnikcr Rd. VII. S.254Verlag Radio-l-oto-Kinotcchnik .Ber lin

IThe Parabollc 24cm PreamplifierlA fully weal her-proofed very hi gh-qu lIlily preamplifie r cove r ing 1200 Ml lz to

1:\60 MI I:l. Mounted in 8 scal ed dlccast enclosure wit h weatherproof N-typesockets for input and output. DC powered via t he out put socket for remot e

mast-head moun ting.

G AIN >40d H across the hand NOI SE FIGU RE d .6d8

£125 + £7.50 post & packing

K M Pu blications, 5 Ware Orchard , Barby, Nr .R ugby, CV2.l 8UF,Tcl :(O)1 7888903~5 1'0,, (0)1788 891 883

179

VHF COMMUNICATIONS 3i95(~ -----------""--""""""==~

Rain", Sf hmijllinR. / )KfJZK

Expansion and Assembly of theDBINV Spectrum Analyser

II is now some time !'o incl' I finis hedworL. on my vcrsion or the spect rumllnlllys('r Irnm UB1N V. ('onslr uclinj;!it Inspired me 10 Come lip with someKddiliona l fea tures, whic h a rc de­scribed bejow.

I.INTRODUCTION

2.IlASIC PR INCII'I.I';S

In the prototype . a ll n BI ;.lV ucvem blic sfor the spectrum analyser were built onorigi na l boards. They funct ion sativtac ­torily, hilt there arc lWO mai n character­istics which see m to require improve­ment. These arc:

For the most part. the expansion fca ­lur es have been borrowed from datad wcls and other publications, so only 3:

general description of their operation i ~

given here. They were a ll assembledtogether on breadboards or dcmon-n a­tion hoa rds; so there are no COr.lpIcICwiring diagram s or hoards. Thi s reportis intended to stimulate interested par­ties to do some development work oftheir own.

I. Frequency stability of seco nd 1.0

2. Precivion of frequency display

Each o f these problems has been climi ­nated by an additional avvcmhly:

1, A frequency contro l unit with mono­flop stabili\at ion.

., A frequency counter triggered b)"Sweep", with a resolution of )00L:Hz for " SpOl O" and 10 L:H 7 for"Zero 'Span",

The following addit ions have also

180

VHF COMMUNICATIONS 3/95

r iR·I :Prototype or the[)BINV Spectr umAnalyser wit h theDK6ZK Additionalfeat ures, sho"'in Jl,Ihe transmis.,loncurve or tan XF9A inlest mode

FiR.2 :Access to uicassemblies below(an he ohtalnl'dthrouah aninsta llat ion platewhich swtngs out

18 1

VHF COMMU NICAlIONS 3/95(~ - - - - - - - - - - ----'-"'--"= = ""'-'= =

OCCli mad... and arc useful in practi­ca l ope ration:

3. !I. 50dO intermediate freq uency am­plifier, adjustable ill 11m steps. so'hat even weaker signals can he..hiftcd right up In 11k' REf Iinc (top)o r 10 the nearest IOdB line. Inconjunction with the REI:·IF.VELdisplay. th is makes il considerablyeasier 10 read off the level . 111isamplifier is also Ol'l' C\-U ry for [he2dn and linear displays (points 4and 5), as these are N "Cd on theREf line!

4 . An addit iona l ci rcu it for 2dBmIVdisplay.

5 . Anl ilo~ amplifier for LINEAR die­play.

6 . Demodulators fer- AM , narrow-bandand broad -hand I-M. for monit oringa sig nal in j'J ~RO SPAN mode.

7. INA pre-amplifier with MMIC(MAR·]) which can he switched on10 improve sen..hivity.

fina lly. we should mention the IOl!ichoard, on which were mo unted thecomponents for the cont rol button sys­rem (hi-stable rela ys), the ele ctronicsfor three displays (SPAN; RBW andREf-] ,[ VEL) and the dii!ilal contro l ofthe 50 dH am plifier. The lash ~r­

formed by this hoard could certainly hecarr ied our more elegantly by a mic ro­con trol ler.

A 101 of wiring and some expensivemul ti-level switches co uld be donewithout if keys and pu lse generatorswere used. Hut I took the conventionalroute here.

J .DESCRII'T101' OF ADIlI ­TI ONAL ASS I':~ II I1 .IES

-'.1. Frl'Qucney Shthili-attion urSecond 1.0

Althou!!h a cer amic resonator i" used inthe second 1.0. the stabitiry is ex ­tremely un..... tisfactory. This is notice­able. part icularly at low display widths.in tha t a signal tcave s the screen a fter 3­

short time or, in narro w-hand monitor­in, in 7ERO SPAN mode. the tra nsmit ­ter hurries through the filter stage .

A remedy can be provided here by afrequency regu lation loop with mono ­flop stabilisat ion. which can be inse rtedinto the original DBINV 00(, asse mblywithout a lterat ions (!),

A circuit which ca n he used withpractica lly no changes can be found inIII . You jus t have to connect a pre­amplifier (NE 5; ( 2) and a divider by 4(2 x H 862 in the prototype unit ) 10 thefirst mixer. Two Itt-turn trimmers :I ~' ­

cessihlc from outs ide make it possibleto mateh the incomi ng tunin g voltageto the valu e supp lied by the mon ofh-pIntegrator in rela tion to posulon anllamplitude. The double mix ing wascarried 0111 to land up in the frequencyrange which was correct Ior the mono­!lop using cheap standard crysta ls. Thecircuit is simply " looped into" theluning voltage circuit. Alte r a wanll-upperiod o f about I hour (drift app . 20klfz), the 1.0 is sti ll running at only afe w hundred liz an hour . Moreover, itwas possible to expand the d isplayrange as far as 5(K) HzIDtV in fourstages. True. tuning beco mes some what

182

VHF COMMUNICATIONS3/95

Fi~.::\ :

The multi-leve lswitches andcOtlp lin~ gea rs orthe ope rationa lcon lrol.. are clearlyvisible

problematic here. hut can still he doncreasonable well. Using the trackinggenera tor as well . it now becomespossible to call)' out even narrow-bandsweeps (e.g. SSM and CW filters).

3.2. The Sw«p-lr i22ul'dF req uency Cou nter

Even in the initial tests of the " origina lversion". displaying the frequency bymeasuring the tuning voltage of thefirst 1.0 with a digital voltmete rseemed rather unreliable . The higherthe frequency rose. thc more the dis­play value was our. Moreover. thevariation in the second LO (alwaysexact ly 3 MH1.) was not taken intoaccount , so that allowances always hadto be made for disp lay errors of a fewMH z due to the hunt ing of the last dig itand the amount of deviati on of thesecond La. So it was only at spansgreater tha n 500 kill /DIV that onecou ld be reasonably certa in that the

frequency displayed was actua lly withinthe display rangc.

For the narrow-band displaying of asignal in an approximat ely known fre­quency range. it was necessary to keydown to it. coming down from the topth rou gh the large span. When relativelynarrow filters are scanned (c.g. short­wave band passes). an externa l marlgenerator would undouhtedly be re­qu ired. The co unter described here(resolu tion )fJO l lll. in SPAN mod e and10 kHz in ZERO SPAN) allows thefrequency to be set rapid ly. even in lowmnges, using an indexed first LO. asthe frequency displayed is now ccr­tain ty within the display rang.e (front 20kHz/D IV upwards). The equipme nt isassembled using 74HCxx modules, withseven 74IIC190' s forming the actua lcounter chain. The signa ls from the twoLO 's, divided by 64, are incrementedor decremented, depe nding on the 11111 ­ing area (norma l or mirror). the secondintermediate frequency being pre-pro-

163

VHF COMMUNICATIONS 3/95(~ --------_---.::!~~~~""'-"~

grammed as either positive or negative ,Through the ceramic resonator used inthe prototype. the second LO osci llatesabove the first intermediate frequency.giving the following calculations forthe two luning areas:

Displayed freq . = l. LO • l.LO + 10.7for "normal" and

Displayed freq = I. LO + 2.LO - 10.7for " mirro r"

If flea market filter cry stals are used,the actual average frequency of theintermediate frequency naturally has tobe dete rmined and programmed (in theprototype unit this amounts to ' 10.68MHz). 111c frequency for the fin! 1.0has already been divided. r OT thesecond 1.0 . there is a second SDA42 12or U664 in the co unter module .

Now, in order 10 obtain a usable resultfrom the counter and a steady display(i f the last digit is d irectly displayed. italways hums through :I few digits. due

to repealed metering), the fina l digit iscertainly counted. bUI is not displayed.For the 100 kHz display. this requires a10 kllz digit. and for the 10 kl b ,d isplay a I kl-lz digit. Due to the64-fo ld division. the gate times are 6,4or 64ms. It can be seen here thai withthis simple design :I 10 kHz display inSPAN mode is no! possible, since thegate time is too long for fast sweeptimes. Triggering takes place throughthe horizontal de flection voltage - ap­proximately 2 mv left of the mid­perpendicular, through an OP wired asa Schmitt trigger. A counting sequenceneeds three sweep passes:

1. Firs! 1.0 COli n!

2. Second 1.0 count

3. Display Latch and SET

At ZERO SPA!". the seventh digit anda to-fo ld divider arc switched onduring the sweep. Moreover. the dim­mer circuit of the sixth display is

Fi~.4 :

Displays an dOperational contro lson th e frunt panel

184

-'-'-"'-""""""'=-'-""="'-----------(~VHF COMMUNICATIONS 3/95

Fig.:': The cxtc rnat ttnptntc housing for the mains transformer can be seen onIhe lert • near 10 it is Ihe Power Supply hoard in the Spectrum Analyser

eliminate d. The counter is now opcrat­ing independently of Ihe sweep andgives a six-digit display of the averagefreque ncy set.

The displays used had integratedlatches and decoders, so as 10 save afurther 6 integrated circuits (for reasonsof space). Natura lly. you can also uselow-cost v-segmcnt displays with de­code rs (e.g. 74H( 45 11) if there isenough room availa ble, or you can adda "second storey" inside the tinplatehousing.

3.3, Th e:,O dB Amplifier at10.7 :\-1Hz

With this amplifier, signa ls of up to ­SOdAm can be shifted individually rightup to the reference line in IdB steps,

and signals at wea ker levels can heshifted to the nearest l Odlt line . Thelevel of a signal on the referen ce linecan now be read off directly on thedisplay. Signals on other lOdB linescan be calculated only in steps of lO.

The amplifier consists of five ident icalstages from [2], which can he adjustedusing PIN diodes. Four of Ihem areresponsible for the 10 dB steps and onefor steps from 0 to 9 (i.e. 49dB in all).Due to the feedback whic h arises, thetwo groups are de-coupled through anattenuetor . The diode currents are setby means of resistances. These arccontrolled by decimal decoders (7442),the data for which arc supplied by linincrementaljdecremental counter, con­trolled by a pulse generator on the logicboard . In addi tion, the REF-LEVELdisplay a lso takes into account the

185

VHF COMMUNICATIONS3195(~ - --- -------"-"--===="-""'"inp ut attenuator, so thai the level isa lways displayed on the top line (REF ­LEVEL), An AGC-ZF·IC (e.g. SLl6 12)can also be successfully used to con­strucr th is amp lifier .

the REF level. Signa ls which lie 16dB(2 dO/DIV) or app. 24dO (J.IN) respec­tively below this level can not bedisplayed.

3.6. ' f he Demod ula tors3.4. 2dB/div Uisphty

This ci rcuit consists of two opera tionalamplifiers. OP I inverts the Y signalsupplied by TDA 1576. OP2 invert sand am plifies by a factor of five. Hotho r's work as adders , so as to he able tofee d in the offset vOlt3¥CS required ineach case, which can he sci throu ghtrimmers. A diode 10 earth at the outputof the second or limhs the signal to ­O,7V. Thus negat ive va lues roo high forfurth er processing in analogue switc hesand in the video filler are 001 reached,and the base line reliably d isappearsfrom the visua l r:mge aga in.

W ith the analyser. we have a receiveroperating continuously from almostzero up to 1,900 Mlt z. So why shoul­dn ' t We also be able just to "monitor"the signals displayed? Four demod ula­tors are availa ble to do th is:

I. AM LOG: Here the a l"..ma ting com­p oncnt which corresponds 10 themodulation is simply cut off. Theincoming signal from the 'rnA 1576is fed in through a ca pacitor to asimple Anti log circuit (transistor atinput of an Or ).

2. AM U N: AM Iracrion of a TDA1220 at 10.7 Mill',

3.~. Linear Display hy means of anAnt ilog Ampli rlcr

3. FM wid e: FM Fraction of aTDA1220 <I t 10.7 MHz

There are certainly specia l integratedcircuu s for this purpose. bUI thesewould have been difflcun for me 10obt ain and wou ld have been veryexpensive. So I just copied the insidesof the ICL804 9 using two OPs and adoub le transistor. Since the antilogam plifier operates negat ively, it can hedire ctly contro lled using the invertedsiJ!nal (rom the 1dO/l) IV stages. Pol­lowing the somewhat ti resome calibra­tion. the visual d isplay unit now gives avolta ge-linear display, i.e. half the leveldisplayed correspond s to -odB.

It should again he pointed out that both2 dB mode and linear mode start from

4. FM narrow: narrow-band FM circuitwith conversion 10 4SS kl lz (Me3357)

The low frequency is released on ly atZERO SPAN and fed into an amplifierin tilt visua l display unit. where there isalso a small loudspeaker. For betterquality an external speaker can heco nnected up and the internal one canhe switched off. All video and low­frequency paths (eve n the video fillerselect ion) are carried hy analogueswitches and multipl exers. so that onlyLX: voltages arc switched. by the opera·tional controls, and so a host ofscreened lines can he dispensed with.

186

Fi~.6 :

Screen photo :Lonzwave i ma~(' ; ont he r-n IJCF77, inthe centre OLFIS.'Spa n: 20 kllz/div

.' .7. Pr e-Amplifier

Before the input siFnal reachl.'!. theDBl NVIX)6 assem bly, it pavscs througha SOdB aucnuator, which can heswitched in IOdB steps, a pre-sele ctor(ready-made filter), and ca n be made:lpp. IOdB hip-her if necessary . This canbe done through an ~1AR-7, the amp li­ficat ion of which varies tly only app.JdB over the entire frequency 13nge.Switching the pre-amplifier on is nottaken into account ill till' REF-LEVELdisplay.

4.MECH ANICAL ASSEMBLY

It is desirable to hom e the ana lysertogether with the trackin g. generator andthe visual display lin it. i.e. independentof a separate osci lloscope, as a com­pact . portable meas uring instrum ent.The starting point was provided by an

existing TEK type 52R visual displayunit , such as arc always availa ble fromflea markets, and a plug-in unit hnus in~

which matcbcs it. Two of these hous­ings placed one on top of the othershould he su ffic ient for the assem bly ofthe analyser plug-in unit ,

A plug-in unit with a double front plateand three insiallauon levels (as therewere seve ral tin plate housings) wasconstructed from aluminium profil es.An additiona l carrie r plate whichswings out m akes it possible 10 reachthe middle "storey" at any lime. eve nduring opera tion .

Corresponding to the size of thc bous­ing, the front plate has dimensions of21Omm. x 125mm . Two correspondingrotary switch pairs (SPAN/R HW andREF-LEVEL/AIT) arc constructed 10

be controlled concentrically by mea nsof gea rs and hollow shafts. The IWO1.0 ·s, together with Ihe sweep. videofilter and demodulators. are operated by

187

VHF COMMUN1CATrONS 3/95

means of control knobs , All otherfunct io ns are carried out through illu­mina ted keys or switches. The frontplate a lso holds the sockets for input(N-type), the calibration generator andthe trac king generator (both nNe Iype),as wel l as four digilal displays (averagefrequency ri-digit ; SPAN, RBW andREf-I.EVEL, each 2·digit , with auxil­iary LED for kl l7jMlI:t, or minus sign).An externa l voltage socket and anaperture for calibrating the intermcdi­ate -frequenc y am plification arc alsoprovided.

During the initial assem bly, the trans­formers (normal shel l-type stampings)were mounted inside the phrg-in unit.But this led to co nside rable ripplevoltages, Now toroidal core transform­ers are used which, together with therectifiers. are externally moumcd in atin plate housing on the back wall o f theplug-in unit. Thi s measure means thereare no longer !lny compo nents carryingmains voltage withi n the unit. Thevariou s photog raphs give an impressionof the mechanical assembly and showthe component de nsity, which is decid­ed ly very high.

The ind ividua l assemblies arc dividedas follows:

On the "top storey" wc have the imagesto ra ge, the operation al control. th e

counter, the first 1.0 and the PLLassembly. The tracking generator. thecalibrator (60 Mllz, - 30dB m), thefrequency stabilisa tion for the secondLO, and the log ic hoard are housed inthe centre. On the swing-om frameplate below arc the high frequency/intermediate frequ ency, the REf-leve lam plifier, the crys ta l filter and thedemodulator unit . The voltage supplyboard is connected with the back wallthrough an aluminium el bow for heatextract ion.

5.LITERATURJ<:

(11 Dr. lng.Jochcn Jirrna nn, DB INV,I\. Spec trum Analyser for theRadio Amate ur, Part3: Co nstrue­tion and PCBsVHF Communica tions 2/ 1989,pp. 108-119

12J Dr.lng.Jochcn Jirm ann, DBl NV,A Spectrum Analyser for theRad io Amateur, Part 'Ia:Construct ion and PCBsVIIF Communications 3!19XlJ,pp, 163-171

188

-;l~.

Very low noise ~eri al amplifil"f for thLcbandas per the YT3MV article on rag90 of VHF Communications 2/92 .Kit col'lwlete wiTh housing An No. 635U8S" . Orders to KM Pubticlllions at Ihaddress shown on the inside cover, (I T (0UKW·Bt richtedlTecl, Pri<"r iflfl"rlt. p&p

VHF COMMUN ICATIONS 3/95

ERRATA

Yes I am afraid that it docs somet imes happen and errors creep into articles . Oftenas not hy my trying to be too cleve r!

In Carl Lodstrom's article in issue 2/95 entitled ' j... Sweep Tuner for the YCO' allreferences to the bias currents in the amplifie rs on page66 and 67 should be in fAand not pA.

Also.on page -29 of issue 1/95 in l ira Otypka's article entitled 'Calculating the Foca lPoint of an Offset Dish Antenn a', the program listing has a few (!) errors. caused hyproblems with my scanner it appears . If anyone would like a copy of the correctprogram listing please contact us.

Apologies again . but it is rare after all!

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Membership is only £9.00 per year.

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189

VHF COMMUNICATIONS 3/95(/0-----------""'-""'~"""'''-'''''~

COMI'LET E KITS

for projects fea tured in VHF Communica tions

KIT I}ES(,RlrTIO~ IS SUE ART No PR IC E

DB I NV-OfI6 Spect rum Ana lyser IF Amplifier 2/R9 n6370 £142.110DB I NV-U07 Spectrum Ana lyser l.o-PI.I . 2/&9 06:l7 1 r 62.IMlI lB 1N V -(XlX Spectrum Analyser Crysta l Filler 3/R9 063 72 £101l ,OODJl! NV-009 Spectru m Analyser Sweep Oen JjX9 06373 .£ 48.00nnrxv.oio Spectrum Analyser Digital Store 3&4/91 0637R £I 3l.00DB IN V-OI I Spectrum Analyser Tracking. Ocn 2/92 06474 £I4 3.<X)DOl NV-0l 2 Spectrum Analyser v e o 1450 MHz 4/92 06483 .£ 39.00DU I NV-Ol J Spectrum Analyser vco 1900 MHz 4/92 06484 1: 4 IJXl

DH6NT- OO I Measuring Amp up to 2.5 GIIz 4/93 06JR2 .£ M .OO

DB6NT- 002 f requen cy Divider 10 5 .5 GUt 4/93 063113 £I OfJ.OJ

DJ8ES-OO! 23cm fM ATV Converter 1/91 06347 e Q) .IX)

nJ8ES-002 Digital Frequency Indicator 1/91 06352 £ 53.00DJ8ES-(XB IF Amplifier 1/91 06355 £ 55.00DJ8ES-004 Dem odulator 1m 06162 £ rz.oo

DJ8ES-0l 9 Tr ansvcrter 144/28 MHz 4/93 06385 £143.00DJ8ES-0I 9mod Transvertcr 50/28 MHz 21lJ5 06392 J.:1 43.00

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De8UG-Om 5W Pi\ for lJcm 3/94 06938 £286.00

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190

VHF COMMUNICATIONS 3/95

KITS and PRINTED CIRCUIT HOARDSfor the Matjaz Vidmar GPS/GLONASS Receiver project

KITSName Issue

S53MV001 1/95S53MVOO2/OO3 l/95S53MV004 1/95S53MVIX15 1/95S53MVOO6 1/95S5JMVOO7 2/95S53MV008 2/95S53MV009 2/95S53MVOlO 3/95S53MVOl1 3/95S53MV013 3fJ5

Description

GPS RF ModuleGPS Converter, Multiplie r & MixerGLONASS RF ModuleGLONASS IF ConverterOLONA SS PLL Synth. ConverterGLONASS Syn thesiserGPS/GT.oNASS Second IFGPS/GT.0NASS nsr ModuleGPS/GI.ONASS CPU BoardGPS/GLONASS 8~key KeyboardGPS/GLONASS PSU and Re set

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Issue Descript ion

PC BOARDS

S53MVOOI 1/95S53MVOO2/00J 1/95S53:MVOO4 1/95S53MVOO5 1/95S53MVOO6 1/95S53MVOO7 2/95S53MVOO8 2/95S53MV009 2/95S53MV01O 3/95S53MVOIl 3/95S53MV013 3/95

GPS RF ModuleCPS Converter, Multiplier & Mi xerGLONASS RF ModuleGLONASS IF ConverterGLONASS PLL Synlh. ConverterGLONASS SynthesiscrGPS/OJ DNASS Second IFGPS/GLONASS DSP ModuleGPS/GIDNASS CP U BoardGPS/nI .ONASS S-key KeyboardGPS/GLONASS PSU and Reset

Art.No

0649006492064950649706499065010650306505065480655006554

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LPGPSLPGLONASS

Complete set of GPS BoardsComplete set of GLONASS Boards

0655706558

£ 83.10£ 124.75

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191

VHF COMMUNICATIONS 3195(+ ---------_....!!.!!---""''''''''''"''''''''''~

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BRI NV Spectr um AnalY!o>Cr Ar l No.

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lX":R1JG-PAne Rt /G..NT

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