Radio Teletype RTTY
Transcript of Radio Teletype RTTY
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KCCV-ARC
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Presentation Agenda
What Is RTTY?1
RTTY Basics2
Hardware and Software3
Tips/Techniques/Resources4
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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
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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
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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
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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
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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
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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
Non-contest: 21.080 to 21.100
Contest: 21.060 to 21.150
Observe the 200 watt output power limit for USA stations transmitting above 21.100
Note PSK-31 operations around 21.070 to 21.072
How Do I Find It?
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RTTY BASICS
20m
Non-contest: 14.080 to 14.100
Contest: 14.060 to 14.120
Avoid the NCDXF beacons at 14.100
Note MFSK-16 operations around 14.080 to 14.082
Note PSK-31 operations around 14.070 to 14.073
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?
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RTTY BASICS
80m
Non-contest: 3.580 to 3.600 (JA 3.520-3.525)
Contest: 3.570 to 3.630
Note PSK-31 operations around 3.580 to 3.582
160m
RTTY is very rare on this band
How Do I Find It?
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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?
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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?
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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???
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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???
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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???
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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
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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
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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.
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SOFTWARE & HARDWARE
Hal DXP38 ($370), excellent decoder
Timewave PK-232 ($530), mediocre RX
Kantronics KAM98 ($400), mediocre RX
TNC - Hardware
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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
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SOFTWARE & HARDWARE
Software TNC engine with Logging program
Software
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SOFTWARE & HARDWARE
Software TNC engine with Contest program
Software
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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
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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.
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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
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Tips/Techniques/Resources
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
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Tips/Techniques/Resources
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.
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