RTTY Contesting Basics. SEDCO 2009 Jim Hall AD4EB Thompson s Station, TN

Transcription

1 RTTY Contesting Basics SEDCO 2009 Jim Hall AD4EB Thompson s Station, TN

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3 What wewill cover today 1. Why Contest using RTTY? 2. What is RTTY? 3. Hardware Interfacing 4. RTTY Software 5. Operating Tips 6. Demonstrations

4 1. Why Contest using RTTY? It really is fun An easy way to get started in contesting It's becoming more popular every year Many RTTY contests to choose from, over 20+ Excellent free software available Chase DX on a new mode Easier than CW Attractive to new and young hams Low pressure Speaking of low pressure, you can actually multitask

5 May 2004 CQ Magazine CQ WW RTTY Contest

6 May 2004 CQ Magazine CQ WW RTTY Contest

7 2. What is RTTY History of Teletype Baudot Code LTRS and FIGS Mark, Space, and Shift Transmitting

8 History of Teletype First machines were mechanical Digital signals transmitted over wire First one built in 1849 Radio teletype started in 1930 s Teletype Model 19 Photo courtesy of KB3RKY

9 From Wikipedia

10 Model 19 Teletype keyboard All letters are capital Similar to regular keyboard Only 31 keys Two characters on most keys Notice FIGS and LTRS shift keys Emile Baudot invented a 5 bit code using shift keys back in 1874

11 Teletypewriter Code - Baudot 1874 Emile Baudot develops 5 element code These machines only had 5 keys, Don Murray develops code for typewriter like keyboard Code used today is ITA2 or the Teletypewriter Code Still uses 5 data bits, but also start and stop bits for improved timing Special characters - LTRS and FIGS A 5 bit code only allows for 32 characters Need 26 letters + 10 numbers + punctuation = not enough Baudot solved this problem using non-printable shift codes LETTERS and FIGURES like the shift key on our keyboards

12 The Teletypewriter Code or Baudot Decimal Hex Octal Letter Figures Binary N/A N/A E LF LF A Space Space S BELL I U CR CR D $ A 12 R B 13 J ' C 14 N, D 15 F! E 16 C : F 17 K ( T 5 Decimal Hex Octal Letter Figures Z " L ) W H # Y P Q O B? A 32 G & B 33 Figures Shift Figures Shift C 34 M D 35 X / E 36 V ; F 37 Letters Shift Letters Shift Each 5 bit value has two characters assigned to it LETTERS and FIGURES shift With the old machines, you had to be aware which shift you were in Computer software now takes care of this shifting for you But noise can mess things up

13 Affect of noise on LTRS/FIGS Missing a LTRS or FIGS character will cause garbage to be printed, until one is received correctly. Example, all OK then missing a LTRS: W FIGS4 LTRSNZ DE W FIGS4 LTRSNL W4NZ DE W4NL W FIGS4 NZ DE W FIGS4 LTRSNL W4,+?3 24NL Noise took out the LTRS, which caused the following characters to print in the wrong shift, until the next shifted character came along. The feature Un-Shift-On-Space (USOS) helps. It forces a LTRS after every space is received. With USOS on, this would have been printed: W FIGS4 NZ DE W FIGS4 LTRSNL W4,+ DE W4NL

14 Radio Teletype - Mark, Space, and Shift RTTY = Transmission of teletype over radio Two constant amplitude signals of different frequencies RTTY sent by alternating between these 2 frequencies Frequencies are called Mark and Space Difference between Mark and Space is called Shift, 170 Hz is standard for amateurs Mark is the higher frequency

15 Transmitting -FSK vs. AFSK Two ways to transmit RTTY Frequency Shift Keying (FSK) Like CW but on-off shifts Mark/Space freq. Audio Frequency Shift Keying (AFSK) Sound card audio fed to rig (LSB) FSK Advantages No messing with audio levels Special FSK RTTY receive filters on some rigs Correct RF frequency displayed on radio (Mark frequency) AFSK Features Simpler to hook up, but Over driving causes splatter More likely to have audio or RF problems Start with AFSK then switch later

16 3. Hardware Interfacing Soundcards Receiving Transmitting -FSK or AFSK AD4EB Setup

17 Soundcards The main reason RTTY has become so popular the past 15 years

18 Receiving Just connect audio from your radio into the soundcard Use constant level output from the radio ACC jack Use your radio AF control for speaker or headphones (as low as possible) Plug into sound card microphone or line-in jack (1/8 stereo), depending on audio voltage levels coming from radio Adjust volume level using sound card driver mixer software (Windows) If ground loop problems exist, use isolation transformer (Radio Shack )

19 Transmitting AFSK Method Audio output from soundcard to radio (microphone or aux input) Should use audio isolation transformer (Radio Shack ) to prevent hum and RF issues May need resistive voltage divider, 10:1 is typical Turn off Windows sounds don t want You ve got mail Keying transmitter two choices VOX is easiest but has pitfalls, beware of transmitting unattended Aquarium sounds PTT signal from a serial port is the best way to go From MMTTY help

20 Transmitting FSK Method Requires available COM ports. Add serial card,or USB to Serial converter FSK from TxD (Pin 3 of 9 pin connector) PTT from DTR pin or RTS (Pin 4 or pin 7) Will need to build a simple interface circuit (may not be needed on Omni VI) Here is the circuit I use, it s from the Digipan software help file. Same circuit Works for TxD. There is good information in the MMTTY help file, and Don Hill s AA5AU RTTY internet site.

21 AD4EB Setup Went homebrew approach I generally operate SO2R in RTTY contests Single Operator 2 Radios (much easier than with CW or SSB) FSK on Icom PROIII, allows use of special twin peak RTTY receive filter AFSK on Omni VI, FSK drifted when radio got warm For more COM ports, added 4 port serial card into PC

22 AD4EB station ready for an SO2R RTTY Contest

23 Interface for Icom ProIII -Includes Tx and Rx Audio, FSK TxD, PTT, and CW.

24 Inside the Icom ProIII interface enclosure

25 AFSK interface for the Omni VI. The microphone pigtail adapter is from my Heil headset. You can buy them from Heil for most rigs.

26 AFSK interface for the Omni VI, with electrical tape removed. Plug is 1/8 mono to plug into Heil pigtail. Voltage divider (1.6:1) and Radio Shack isolation transformer.

27 USB-to-Serial converter for laptop. Also shown is a CT-17 Icom level converter for polling Icom radio information.

28 4. RTTY Software The other reason for the dramatic growth in RTTY operators Really great software available, easy to use and free Will demonstrate the software I use, MMTTY and N1MM MMTTY Written by JE3HHT Makoto Mori Free Google MMTTY, download latest version, installs in 1 minute. 99 percent of the default options are what you want to use Activate the XY scope, large size, to aid in tuning signals Set ways to send to word out, so you can correct your mistakes Most important settings are found via Options -> Setup Excellent help file should answer all your questions, if not try MMTTY users group Great for rag chewing, DXing, or just learning RTTY Get used to MMTTY first, then try N1MM for contesting

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30 N1MM Written by N1MM Tom Wagner plus many others -Free Incorporates MMTTY Follow the N1MM quick start guide Works with VISTA N1MM digital users group for help Ted W4NZ or myself (AD4EB on QRZ.com) will also help Writelog is also popular for RTTY contesting N1MM Live Demo

31 AD4EB -N1MM set up for SO2R, primary computer monitor

32 AD4EB - N1MM set up for SO2R, secondary computer monitor

33 5. Operating tips RTTY is 100 percent duty cycle Check what your radio and amplifier can handle ProIII Full power OK, powerful internal fan Omni VI Heat sink only, so use external muffin fan Centurion amplifiers, run 50% (500W) Always use spaces around each word or callsign, and make sure it is the first and last character you send. No signal present will print gibberish K4RO becomes ASDFK4RO or K4ROGHJK Check your macros

34 Hey, you re just sending a solid tone Wired for AFSK, but transmitter set to RTTY (FSK) MMTTY COM port not set properly Hey, you're not on frequency RIT may be off zero If AFSK, MMTTY AFC may be on and drifted off 2125 Hz If AFSK and using AFC (not recommended), NET must be on Hey, you're splattering all over AFSK volume set too high AFSK cable picking up RF, use ferrite choke Use isolation transformer

35 Use narrow filters Normally use 500 Hz, especially when S&P When Running and crowded, use 250 Hz For weak signals I use PROIII dual peak filters, not for S&P MMTTY s band pass filter BPF also works well Keep transmissions short Example: You have a good Run going, when someone answers your CQ like this : AD4EB AD4EB de XXXXX XXXXX XXXXX PSE K Wastes time, and others waiting in line will leave XXXXX XXXXX is all that is needed For exchange send 599 only once, remaining twice Observe others, then emulate what the best ops are doing

36 Set up macros for partial repeats Set up for each portion of the exchange JIM JIM and TN TN for example Set up macros for partial requests For each portion of the exchange with? NAME?, SEC?, NR? The most important tip of all is to Have Fun!! And, don't worry about making mistakes, or perhaps slowing someone down. If you're a new call on RTTY, you will be appreciated and encouraged to continue.