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Re: Filter and CW Questions

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  • Steve Yates
    Hi Ryan, I have the W4RT 300 Hz filter in my FT-897D that I bought a year ago. I ve operated just about every CW contest since then and the rig performs well.
    Message 1 of 3 , Feb 28, 2009
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      Hi Ryan,

      I have the W4RT 300 Hz filter in my FT-897D that I bought a year
      ago. I've operated just about every CW contest since then and the
      rig performs well. There is a bit of propagation delay through the
      mechanical filter and this causes a delay in the AGC loop. This
      manisfest itself as a slight pop at the begining of characters in
      fast AGC. This isn't unusual and probably occurs in most rigs. The
      addition of the DSP filter totally removes the pop.

      The only performance degradation I've ever notice with the FT-897 was
      caused by the AGC being pumped by interfering signals (AGC blocking).
      This is really a problem when using the DSP filter since it operates
      outside the AGC loop so filtered signals will still activate the
      AGC. The 300 Hz filter helps tremdously in this regard. However,
      even without the mechanical filter and just the DSP filter you can
      mitigate the problem by cranking back the RF gain until the AGC is at
      the level of the offending signals and simply compensate for the loss
      by cranking up the AF gain. Not perfect but will work amazingly
      well. For me this procedure increases the dynamic range of the
      detected audio and gives the filter between my ears more data to work
      with in decoding CW amongst many stations.

      In regards to full break-in operation the rig was designed for it so
      I wouldn't think you should 'expect' damage but since the relay is a
      mechanical device there is probably some wear on the contacts over
      time. I use full breakin during contests and working DX and set the
      delay for about 500 ms for the rest of the time. In case you haven't
      noticed, the relay is not in the circuit on 2m and 70cm making full
      break-in on those bands very quiet. Of course you probably won't get
      many pileups there but I did use QSK during the August UHF contest.

      In regards to the DSP slowing down the rig during QSK I have no idea
      what you mean. I reckon I haven't experienced that one.


      73,
      Steve Yates - AA5TB



      http://www.aa5tb.com/
      http://groups.yahoo.com/group/NORTEX_QRP/
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