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Weird PSK no-decode problem, any ideas?

Discussion in 'Working Different Modes' started by N6PL, Oct 7, 2019.

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  1. N6PL

    N6PL Ham Member QRZ Page

    I'm no newbie, been using various digital modes for many years but this one has me stumped. I'm unable to decode any PSK signals using an Icom 706MkII and any software (have tried both Digipan and MixW). It is not the computer, I have tried two and the problem doesn't change. Either will decode properly using a mic and any PSK recording from the Internet, but not when connected to the radio. I have tried multiple audio interface units including a simple cable directly from the headphone output of the radio to the computer line input, but no change. I have also tried an outboard USB audio card, same problem (but I know it's not the computer anyway since it can decode PSK audio from other sources using the internal soundcard.) It is not a simple level problem, I have tested that thoroughly. The waterfall display doesn't look entirely normal (I see various PSK signals across the passband as expected but the traces are indistinct and the tuning indicator will not lock, no doubt why I cannot decode anything.)

    This pretty much leaves some issue with distorted radio audio as the only possible culprit, but not sure how that is possible. The audio out of the radio sounds normal to the ear and the radio seems to operate normally in all respects, and no issues are evident when using SSB phone. On a 706MkII there are no SSB audio adjustments available to cause problems, and of course DSP and any filters are disabled. It's a simple radio and seems to be working fine, except...

    Really pulling my hair out over this. Unfortunately I don't have another radio to try where I am right now, and I can't find anything obviously wrong with the IC-706 I'm using (have used the same radio in the past on PSK without problems but recently pulled it out of storage and put it back into service.)

    Any ideas?
     
  2. KF5FEI

    KF5FEI Ham Member QRZ Page

    I had a Samsung netbook with audio issues and PSK-31 using a PSK-20 radio (audio in / out via cables) . If you listened to the audio from the radio on the PC speakers, it sounded fine. If you recorded the audio and tried to play it back, it sounded like caca. However, an external USB audio device did the trick. The one and only time I ever called factory support, I was directed to a secret driver download area and assured it would solve the issue. Nope.
     
  3. KB0MNM

    KB0MNM Ham Member QRZ Page

    Maybe you need to look at the end of this thread: https://forums.qrz.com/index.php?threads/spectrum-display-texting.652398/#post-5017455
    They were talking about the inclusion of Reed-Solomon coding and programs which support 'automatic signal identification'. So have you tried using MultiPSK and are you certain that the signals sent are indeed PSK-31? If that is the case, then maybe there is a bandwidth filter set incorrectly in the 706MkII. You may be able to find more info here (on QRZ) using the search box here in working different modes. Information on other radios sometimes includes the names of settings to check, so other amateurs with PSK-31 problems ( solved ) might have the hint that you need.
     
  4. KE5MC

    KE5MC Premium Subscriber QRZ Page

    Any chance you are receiving on the wrong sideband?
     
  5. AG6QR

    AG6QR Premium Subscriber QRZ Page

    That's a good thing to check for many modes, but the choice of sideband doesn't matter for PSK31. A 180 degree phase shift is a 180 degree phase shift, regardless of the sideband used.
     
  6. N6PL

    N6PL Ham Member QRZ Page

    ARRRGGG, this is so embarrassing but I was actually hearing FT8 traffic (which doesn't work very well with a PSK31 decoder ;)) I have been off the air for a couple of years and the amount of activity threw me, there was so much that I jumped to the conclusion it was PSK31 even though it sounded a bit off, and of course the short transmission bursts should have been a clue. FT8 sure seems to have become popular these days.
     
  7. KB0MNM

    KB0MNM Ham Member QRZ Page

    And here I was just thinking about your problem:
    http://www.packetradio.com/PSK31.htm ( General cabling for radios without TNCs built-in, Settings for HF )
    http://www.packetradio.com/sb16rads/ISOKITS/isokit_5_ic.gif ( Icom- other rigs eg.746 cabling- ground loop isolation eg. noise caused by improper grounds fix )
    That is where SIAM ( as done by the Reed-Solomon coded preamble ) can be pretty handy.... Back in the day that there were only a dozen or so digital modes, the firmware in a PK-232 could do this for you. There is a PK-232 Facebook group now... good fun.
     

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