Digital mode questions

Discussion in 'Working Different Modes' started by KJ4PSU, Jun 7, 2010.

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  1. KJ4PSU

    KJ4PSU Ham Member QRZ Page

    I have begun to tool around with digital modes in ham radio. I dont have the equipment currently to get on the air but I am using a shortwave radio and my computer to "listen" in on digital modes. I downloaded a free program called truetty and have it up and running.....only problem is that I have not been able to make sense of what is coming across the screen. Is there something I am missing to make sense of the data coming through? I am only getting random characters and letters. Any help is appreciated.

    73
    Will
     
  2. KJ4RZZ

    KJ4RZZ Ham Member QRZ Page

    You'll need to make sure you are in the correct mode. For PSK31 (a very popular digital mode), you can try 28.120 during the late afternoon. You will hear PSK as a sort of a modem like sound which will come in a short burst of say 10 to 30 seconds. When you hear it, quickly find and select it in the waterfall, you should see the characters. Adjust the squelch (in the program not the radio) until the random letters stop when there is no data transmission.

    Occasionally you will hear other noises and squeals which sound like data signals... often they are not. You can tell because they will always be there, on the same frequency, day or night.

    Digital QSOs are often filled with code abbreviations so it can be cryptic if you are not familiar with code... ex KJ4PSU DE KJ4RZZ UR RST 599 599 BTU KN

    RTTY is common also, but is a bit more "noisy".
     
    Last edited: Jun 7, 2010
  3. KL7AJ

    KL7AJ XML Subscriber QRZ Page

    Hi Will:

    You have to be sure you match the digital mode to the sound card program. The problem with random shortwave bands is that there is a LOT of stuff out there that's either encrypted or on modes for which there is no amateur equivalent.

    One sure bet, however, is the WEFAX broadcasts in the 8MHZ area. I believe 8146 is around where the Coast Guard hangs out. It's a pretty unmistakeable signal, and the high rez satellite photos you can get are great. (SLOW, but great. :) )

    You might also look for FEC AMtor (actuallly SITOR) broadcasts in that region. Lots of maritime weather forecasts and such.


    And don't forget the W1aW digital brodcasts....lots of them and always on time. Check W1AW for the schedules...they have amtor, RTTY, and ASCII broadcasts, as well as PSK31.

    Eric
     
  4. KL7AJ

    KL7AJ XML Subscriber QRZ Page

    Ooops...I forgot W1AW dropped their ASCII broadcasts in favor of MFSK 16.

    Eric
     
  5. KJ4PSU

    KJ4PSU Ham Member QRZ Page

    I am tuned into the ham bands on the sw radio. Currently I am sitting on 14.075 usb with the radio connected to my computer. I see the waterfall but still have a bunch of random characters being spit out.
     
  6. KL7AJ

    KL7AJ XML Subscriber QRZ Page

    Be sure you're on BPSK31. (A few hams run QPSK31, but that's a small minority) Be sure the program is not set for REVERSED sideband (though on PSK31, the programs can usually figure that out on their own)..and I'd center tune on 14.070, not 14075....you might be looking at some other odd modes there.

    Eric
     
  7. KJ4RZZ

    KJ4RZZ Ham Member QRZ Page

  8. KC2UGV

    KC2UGV Ham Member QRZ Page

    Did you put the decoding crosshairs on top of the "traces" (Yellow - red tracks going down the waterfall)?

    Also, bump the software squelch up when you are on a blue area of the waterfall until you don't see any letters.
     
  9. AG3Y

    AG3Y Guest

    Check out this page, it should be helpful!

    http://www.wb8nut.com/digital.html


    Slight clarification PSK-31 is NOT phase sensitive, you can tune it in with either USB or LSB! QPSK, however, IS , as are many of the other modes! If you are sure you are right on the right frequency, but decoding gibberish, see if you can reverse the sidband on the receiver, or click a "reverse" button in the software. Either way should help you to start seeing plain text.

    Good luck. Jim
     
  10. M0WAN

    M0WAN Ham Member QRZ Page

    Are you actually on BPSK31 transmissions? These appear as the narrowest traces on the waterfall. Any others will produce nonsense.
     
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