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Possible fix for RX problems with the T2-135

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  • mulveyraa2
    Hi All: I just purchased a used DR-135T and T2-135. One thing I noticed after setting it up was that there were a LOT of FCS errors, even on packets that
    Message 1 of 2 , Nov 1, 2007
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      Hi All:

      I just purchased a used DR-135T and T2-135. One thing I noticed
      after setting it up was that there were a LOT of FCS errors, even on
      packets that sounded relatively strong & clean. For example, at one
      point, I had about 15 received packets, and 300 FCS errors. Most of
      the packets that I could hear well on another comparable receiver were
      not being decoded by the T2-135.

      After playing around with the rig a bit, I set it to "narrow" mode.
      ( Hold-F + MHZ ).

      The RX packet count because MUCH, MUCH better. Now the RX count is
      running about twice the number of FCS errors. And I think that the
      FCS count is somewhat spurious, too, since I can see it incrementing
      on occasion even when no packets are audible. Nonetheless, most real
      packets are now decoding.

      There doesn't seem to be any other issues using narrow mode - my
      transmitted packets are all being decoded fine, etc.

      Hope this helps some of the people who were mentioning decoding
      problems on their T2-135's, in the past.

      - Rich
    • Scott Miller
      I didn t even think of that - I think all of my test units have probably been set to narrow all along. I ll run some tests and come up with some
      Message 2 of 2 , Nov 1, 2007
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        I didn't even think of that - I think all of my test units have probably
        been set to narrow all along. I'll run some tests and come up with some
        recommendations for the manual.

        The FCS count will tend to be a bit high - the clock recovery code
        allows a LOT of slop in the timing, so a certain amount of noise will
        register as valid long enough to add up to the minimum 18 bytes or so
        needed to trip the FCS counter.

        Thanks,

        Scott

        mulveyraa2 wrote:
        >
        >
        > Hi All:
        >
        > I just purchased a used DR-135T and T2-135. One thing I noticed
        > after setting it up was that there were a LOT of FCS errors, even on
        > packets that sounded relatively strong & clean. For example, at one
        > point, I had about 15 received packets, and 300 FCS errors. Most of
        > the packets that I could hear well on another comparable receiver were
        > not being decoded by the T2-135.
        >
        > After playing around with the rig a bit, I set it to "narrow" mode.
        > ( Hold-F + MHZ ).
        >
        > The RX packet count because MUCH, MUCH better. Now the RX count is
        > running about twice the number of FCS errors. And I think that the
        > FCS count is somewhat spurious, too, since I can see it incrementing
        > on occasion even when no packets are audible. Nonetheless, most real
        > packets are now decoding.
        >
        > There doesn't seem to be any other issues using narrow mode - my
        > transmitted packets are all being decoded fine, etc.
        >
        > Hope this helps some of the people who were mentioning decoding
        > problems on their T2-135's, in the past.
        >
        > - Rich
        >
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