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71939Re: How should I set the input level to my sound card for best RX(TX) performance?

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  • warrenallgyer
    Jan 24, 2013
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      I have done some work overnight to try to correlate a WSPR noise level of "0" to an actual noise level on HDSDR.

      It seems pretty consistent: Using the sound card input level to adjust for "0" during WSPR receive, then switching to HDSDR, the noise floor seems to be about -90 dBm. So it seems WSPR wants to see that level of noise to be comfortable.

      I have not figured an objective way of comparing WSPR decodes at this level versus the minimal setting I am using now as a norm. My gut tells me the minimal setting misses some decodes that I get with having a -90 noise floor but I cannot be sure.

      Warren Allgyer - W8TOD

      --- In softrock40@yahoogroups.com, David Turnbull wrote:
      >
      > On Thu, Jan 24, 2013 at 1:01 AM, Alan wrote:
      > > I'm puzzled by your WSPR-IQ comment. Is this a fault in WSPR?
      >
      > WSPR doesn't seem to find signals that are more than 20dB away from
      > it's arbitrary 0dB level. You can see them clearly in the waterfall.
      > They just don't decode. If you do the OpAmp gain mods then the noise
      > meter in the lower left always stays red with more than -20dB. By
      > using HDSDR or PowerSDR, you can manually set the gain and turn off
      > AGC. This VAC method seems to always outperform the I/Q mode anyways.
      > I suppose if your line-in volume has gain instead of attenuation then
      > you could fix it there too.
      >
      > 73 David AE9RB
      > http://AE9RB.com/
      >
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