Radio Teletype RTTY - Dave Kalahar Teletype RTTY.pdf [email protected] RTTY BASICS RTTY transmission...

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Presentation Agenda

What Is RTTY?1

RTTY Basics2

Hardware and Software3

Tips/Techniques/Resources4


What Is RTTY?

Landline teleprinter operations began in 1849 when a circuit was put in service between Philadelphia and New York City. Émile Baudot designed a system using a five unit code in 1874 that is still in use today.

Radioteletype evolved from these earlier landline teleprinter operations. Commercial RTTY systems were in active service between San Francisco and Honolulu in as early as April 1932.

RADIOTELETYPE

http://en.wikipedia.org/wiki/%C3%89mile_Baudot


RTTY BASICS

RTTY transmission is a continuous carrier which shifts frequency between two distinct frequencies

The lower RF frequency is known as the SPACE

The upper RF frequency is known as the MARK

The difference between the two is known as the SHIFT

Using FSK a RTTY transmission at dial setting 14.090

Mark frequency is 14.090

Space frequency is 14.089.830

Shift is 170 Hz

Characters sent at 45 baud or 1/6 second per character or about 50 words a minute.

Mark and Space


RTTY BASICS

http://rfwireless.rell.com/pdfs/TN_WJfsk.pdf

http://rfwireless.rell.com/pdfs/TN_WJfsk.pdf


RTTY BASICS

RTTY uses the 5-bit ITA2 code

5 bits means only 32 characters can be represented

To get around this there are two “sets”, Letters and Figures

Each set uses 26 characters plus 6 common entries

Letters mode

“A” through “Z” (26 CAPITAL letters)

Ltrs shift, Figs shift, null, space, carriage return, line feed

Figures mode

“0” through “9”, various punctuation (26 characters)

Ltrs shift, Figs shift, null, space, carriage return, line feed

Figures Shift and Letters Shift latches which set displayed

Letters and Figures


RTTY BASICS

The Letters Shift and Figures Shift do not print

The code for the character “Q” and “1” are the same, which one prints depends on if you are in Letters or Figures mode

Note that the space character appears in both sets

Example: “W6ZZZ DE KD HXT” gets sent as:

LS W FS 6 LS Z Z Z space D E space K D FS 4 LS H X T

Why do we care to understand this???

If a burst of static garbles the LS or FS character what prints after that is from the wrong set until the next LS or FS character appears

Letters and Figures Example


RTTY BASICS

If numbers are sent in Letters mode you can translate

“TOO” is “599”, “PPQ” is “001” (note that “-” is “A”)

In some programs a “right-click” will translate the word

Northwest Rule for Numbers


RTTY BASICS

10m

Non-contest: 28.080 to 28.100

Contest: 28.060 to 28.150

Note PSK-31 operations around 28.120 to 28.122

15m


Contest: 21.060 to 21.150

Observe the 200 watt output power limit for USA stations transmitting above 21.100


How Do I Find It?


RTTY BASICS

20m


Contest: 14.060 to 14.120

Avoid the NCDXF beacons at 14.100

Note MFSK-16 operations around 14.080 to 14.082


40m

Non-contest: 7.025 to 7.050 kHz and 7.080 to 7.100

Contest: 7.025 to 7.100

Note PSK-31 operations around 7.035 and 7.080

How Do I Find It?


RTTY BASICS

80m

Non-contest: 3.580 to 3.600 (JA 3.520-3.525)

Contest: 3.570 to 3.630


160m

RTTY is very rare on this band

How Do I Find It?


RTTY BASICS

Of all the digital modes on HF, RTTY is very distinctive and not easy to confuse with other digital signals.

What Does It Sound Like?


RTTY BASICS

Accurate frequency tuning is an ABSOLUTE MUST

Listen to the audio signal to help yourself tune

Listen to the audio to detect transmission starts and stops

Turn off distractions like AFC and NET in your software

Use FSK and a 250 or 500 Hz filter (when using AFSK some radios only allow you to use the wide SSB filters)

Use tuning “aids” provided in software.

How Do I Tune It In?


RTTY BASICS

Decide whether to use AFSK or FSK.

The difference is in the transmit path.

AFSK = audio frequency shift keying

Mark (2.125kHz) and Space (2.295kHz) audio signals generated from TNC/sound card to AFSK input on radio.

FSK = frequency shift keying

Digital signal generated from TNC/serial port to FSK input on radio. Causes radio to shift TX frequencies between mark and space.

FSK or AFSK???


RTTY BASICS

Why use FSK?

Ability to use your CW filters in most rigs

Easier than AFSK to set up

Why use AFSK?

If your rig doesn’t have an FSK input

Same interface as PSK31

Ability to use AFC

FSK or AFSK???


RTTY BASICS

Potential for TX signal problems with AFSK

RF, ground loops: isolation transformers

Turn OFF speech compression, Hi Boost

Check sound card audio levels, mute unnecessary channels

Watch MIC gain, ALC

Use LSB

AFSK Issues


RTTY BASICS

RTTY Polarity:

No common FSK input polarity standard by rig manufacturers across product lines.

Adjust with rig menu command, rig jumper, or software.

Use LSB for AFSK on all bands!

Use 170Hz shift. Ham RTTY Standard.

FSK Issues


GET ON THE AIR

TNC or Terminal Node Controller.

Either a hardware or software TNC is

needed.

Software for command and control of

TNC and logging of contacts.

Interface between the radio and

TNC. Simple or complex.


SOFTWARE & HARDWARE

Hal DXP38 ($370), excellent decoder

Timewave PK-232 ($530), mediocre RX

Kantronics KAM98 ($400), mediocre RX

TNC - Hardware


SOFTWARE & HARDWARE

MMTTY (free), excellent decoder, tuning indicator, decoding profiles

WinRTTY (with Writelog), good decoder

RITTY ($100), best decoder, but difficult to set up, requires ISA sound card, no future support

TNC - Software


SOFTWARE & HARDWARE

Software TNC engine with Logging program

Software


SOFTWARE & HARDWARE

Software TNC engine with Contest program

Software


SOFTWARE & HARDWARE

Homebrew

Lots of schematics on web

Pre-made (Computer Soundcard)

KK7UQ Model II Kit ($55)

Bux Comm Rascal MV+ ($50)

Bux Comm Rascal Kit ($20), no FSK

RIGblaster+ ($140)

Tigertronics SignaLink SL-1 ($60), no FSK

…and MFJ

Pre-Made (External Soundcard)

MicroHAM line ($330 - DigiKeyer)

Rig Expert ($200)

US Interface Navigator ($420)

Interface


Download

Read

Install

Interface

Operate • Operate and have fun with RTTY. See you on the air.

• Interface from your computer to radio with shielded audio

cables for both receive and transmit.

• Install the software as directed. Get a good understanding

of your computers COM ports.

• Read the documentation included with MMTTY or AA5AU’s

excellent http://www.aa5au.com/GettingStartedOnRtty.pdf

• Download MMTTY and all the help files available. A copy is

provided on the CD or http://mmhamsoft.amateur-radio.ca/.

GET ON RTTY FOR FREE

With available free software and 2 audio cables, you

can be on RTTY this weekend for practically free.

http://www.aa5au.com/GettingStartedOnRtty.pdf

http://mmhamsoft.amateur-radio.ca/




Tips/Techniques/Resources

Tips Techniques Resources



Tips

RF IssuesIf you have any RF interference

leaks, RTTY will find them.

Get some chokes on hand.

FSK and USB SerialSome USB to serial port converter

cables won’t work for the FSK signal

due to problems with 5-bit RTTY

USB converter is OK for PTT, and rig

control. The all in one interfaces fix

this problem.

See AA5AU web site



Techniques

MacrosCan’t type? No problem, use

macros' built into nearly every

software RTTY program.

FilteringYour narrow (500hz or better) CW

filter works great on RTTY.

CW Type OperationIt’s common to use CW style and

abbreviations when operating RTTY.

EX: W6WTG DE KD4HXT TU UR

599 599 QTH CA CA NEAR

BAKERSFIELD OP DAVE DAVE SO

HW? W6WTG DE KD4HXT KN



Resources The Web

AA5AU, Don Hill

http://www.aa5au.com/rtty.html

http://www.rttycontesting.com/

K4WW, Shelby Summerville

http://www.rttyinfo.com/

The CDWe’ve provided a CD with this

PowerPoint presentation and a

collection of useful software and

files we talked about today.

http://www.aa5au.com/rtty.html

http://www.rttycontesting.com/

http://www.rttyinfo.com/

www.w6lie.org

Radio Teletype RTTY - Dave Kalahar Teletype RTTY.pdf [email protected] RTTY BASICS RTTY transmission...

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