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Audio bandwidth problem

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  • Phil Reed
    I ve been trying to get my first WSJT contact via meteor scatter, and I may have detected a potentially interesting problem. The received audio from my IC-251A
    Message 1 of 3 , Jul 28, 2004
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      I've been trying to get my first WSJT contact via meteor scatter, and I may
      have detected a potentially interesting problem. The received audio from my
      IC-251A tails off dramatically above about 1200 Hz, to the point where the
      high frequency tone seems to be nearly inaudible. I hear the pings, but
      they don't decode, and looking at them with a spectral analysis shows a
      dramatic loss in amplitude. This is apparent even when I look at channel
      noise. The problem may also be present on transmit audio.

      Anybody got any ideas on how to punch up the upper audio frequencies? (The
      sound card is a Creative SB Live.)

      Thanks in advance.

      --

      ...phil / w8sca

      "For a list of all the ways technology has failed
      to improve the quality of life, press 3."
    • Mike(W5UC) & Kathy(K5MWH) Watson
      Phil, this is only a guess, but I would bet that the problem is in your IC-251 rather than the sound card. I have a IC-271 that I was using on 2M, and it will
      Message 2 of 3 , Jul 28, 2004
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        Phil, this is only a guess, but I would bet that the problem is in your IC-251 rather than the sound card.  I have a IC-271 that I was using on 2M, and it will not send the 73 tone in FSK441.  The audio response just isn't there.  Tune in a good clean carrier and vary the frequency so the output tone varies.  Then measure as best you can, the audio output tone level at various frequencies.

        73
        Mike, W5UC



        At 09:03 PM 7/28/2004 -0400, you wrote:
        I've been trying to get my first WSJT contact via meteor scatter, and I may
        have detected a potentially interesting problem. The received audio from my
        IC-251A tails off dramatically above about 1200 Hz, to the point where the
        high frequency tone seems to be nearly inaudible. I hear the pings, but
        they don't decode, and looking at them with a spectral analysis shows a
        dramatic loss in amplitude. This is apparent even when I look at channel
        noise. The problem may also be present on transmit audio.

        Anybody got any ideas on how to punch up the upper audio frequencies? (The
        sound card is a Creative SB Live.)

        Thanks in advance.

        --

                                          ...phil / w8sca

        "For a list of all the ways technology has failed
             to improve the quality of life, press 3."



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      • Bruce Brackin
        Phil - I have/had similar problem with Kenwood TS-60S I used. It rolls off on higher audio frequencies also. You can adjust the 4 tones for TX fairly easily
        Message 3 of 3 , Jul 28, 2004
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          Phil - I have/had similar problem with Kenwood TS-60S I used. It rolls
          off on higher audio frequencies also. You can adjust the 4 tones for TX
          fairly easily as described in the WSJT manual. In short, connect dummy
          load and watt meter and see what you get on the A, B, C, D tx buttons.
          Select the lowest one on output (usually the D/73 tone) and then play
          with "FSK441 Amplitudes" in Setup Options (F2) for the other three
          tones. The settings seem to be very nonlinear so it may not take much
          reduction below 1.0 to get the levels down to match the lowest response
          tone. I didn't have too much trouble with the receive curve on the
          Kenwood. You might try IF Shift or something similar if the set has it
          to see what effect that might have on Rx response.

          GL - Bruce, N5SIX
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