Loading ...
Sorry, an error occurred while loading the content.

Re: [dxatlas] Re: Decoding performance

Expand Messages
  • Pete Smith
    ... Hi Bill - I think you may need to do some experimenting to maximize Skimmer s weak-signal performance. I may have mentioned this already, but a great deal
    Message 1 of 19 , Apr 26, 2008
    • 0 Attachment
      At 09:20 AM 4/26/2008, bill_w4zv wrote:
      >How do you feel about Skimmer's ability to decode weaker signals in
      >QSB and QRN? I'm somewhat unimpressed so far but it could be I'm not
      >doing something right. Does the DSP filter width affect all decoders
      >or just the one displayed with the green bar? Based on what I've seen
      >so far, Skimmer would be great for identifying strong stations CQ-ing
      >or in a pileup but it doesn't work very well for weaker signals, which
      >would likely be the very ones you want to know about. But this could
      >be due to my not setting Skimmer up correctly or due to my weak
      >computer.

      Hi Bill - I think you may need to do some experimenting to maximize
      Skimmer's weak-signal performance. I may have mentioned this already, but
      a great deal depends on the dynamic range of the line input of your
      soundcard. Whichever card you use, you need to make sure that the input
      gain is set just short of clipping, in order to get the closest possible
      approximation of the sensitivity of the receiver alone. and of course, you
      are comparing it with one of the best receivers ever made - no fair hi.

      73, Pete N4ZR
    • Pete Smith
      ... One of the most effective tricks is to uncheck the Adaptive decoder box, and set a specified maximum number of decoders. Hitting 100% isn t so
      Message 2 of 19 , Apr 26, 2008
      • 0 Attachment
        At 02:01 PM 4/26/2008, rt_tclay wrote:
        >If on your computer Skimmer is reaching 100% cpu, then yes, it is
        >having to reduce the number of decoders. I don't know the algorithm
        >used to do that, but yes, it might do that based signal strength. Try
        >reducing the bandwidth. My old 1GHz Athlon can't keep up with 96 KHz,
        >but is ok at 48 KHz if the band isn't too busy.


        One of the most effective tricks is to uncheck the "Adaptive" decoder box,
        and set a specified maximum number of decoders. Hitting 100% isn't so
        important, in my view, as eliminating most of the junk you get from
        Skimmer's trying to decode on RTTY signals. If you set a maximum number of
        decoders, Alex says that Skimmer accommodates that by narrowing the band of
        frequencies that it attempts to decode, centered around the center
        frequency of the waterfall display. Experimentally, I discovered that 150
        decoders seemed pretty much to eliminate anything above about 14060 on a
        normally busy weekend band, when I set the waterfall on 14030. Today,
        running 300 decoders, I'm getting a lot of "AA4EE" type "callsigns" in the
        14070 and above range. During a major contest, you might have to set it to
        a higher number to get the same approximate frequency coverage.

        73, Pete N4ZR
      Your message has been successfully submitted and would be delivered to recipients shortly.