71939Re: How should I set the input level to my sound card for best RX(TX) performance?
- Jan 24, 2013I 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 firstname.lastname@example.org, 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
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