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2633Re: [tracker2] T2 demod questions

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  • Scott Miller
    Dec 2, 2007
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      The EQ jumper is in the input filter section, near C2 and C3. It just
      switches C3 into the audio input path and flattens the filter response.
      It's pretty close to the circuit used by the KPC-3 and I think some of
      the TNC-2 clones as well. Somewhere around here I've got plots of the
      frequency response from the Spice simulation.


      Tim Smith wrote:
      > Hi Scott:
      > I was looking at the schematic in the YahooGroups file area to try
      > and see what the EQ jumper actually does. I am missing a few packets
      > from time to time as compared to another TNC that is running a legacy
      > XR2211 demod.
      > I'm looking at audio on both sides of the EQ jumper with and without
      > the jumper and see no difference in how the mark/space tones are
      > handled. I've tried a variety of input levels from an Alinco DR1200
      > data radio. The T2 demod is hearing with a pretty wide dynamic range
      > from 200 mv to over 2v ptp. Live stations out there (around here)
      > range from 300 mv to 2v ptp and am decoding packets at both extremes.
      > I can't find the EQ jumper in the schematic to see what it's supposed
      > to do. Presently, makr/space tones are pretty close in amplitude
      > with a couple of ststions a bit hot on the 1200 hz tone (but no more
      > than 30% difference).
      > Is there an updated schematic and a better explanation of what the EQ
      > jumper is doing?
      > Thanks,
      > Tim
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