Message-ID: <4AAB9D71.2070507@charter.net>
Date: Sat, 12 Sep 2009 09:09:05 -0400
From: John Andrews <w1tag@charter.net>
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To: rsgb_lf_group@blacksheep.org
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Subject: Re: LF: Re: WOLF/WSPR Sound card issues
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Dave,

The deviation of the actual sampling rate from the nominal (8000, 11025, 
etc.) have always been an issue for low bit-rate sound card modes. The 
newer schemes may produce wider excursions, but that is a problem only 
if you aren't correcting for it.

WOLF has an obvious way to compensate for the actual sound card sampling 
rate, and once you have done it, the performance will be just as good as 
it would be if the rate were exactly equal to the nominal. If you have 
an accurate tone source, just use it in the WOLF calibration process, 
and you'll be all set. Other tone sources include Loran-C and 
divided-down outputs of higher frequency well-calibrated oscillators.

As you point out, the WSPR program does not seem to have a way to 
compensate for far-off actual sampling rates. But WSPR's author, K1JT, 
has a jack-of-all-trades program called WSJT that DOES allow for 
calibration. WSPR is one of a number of modes offered in WSJT. So, that 
might be a way out for those stuck with on-board audio setups.

That said, I've never had a sampling rate issue with WSPR on any of my 
various computers, a couple of which sample pretty far off the mark.

If you think this stuff is fussy, try BPSK at 1 bit/sec where your only 
adjustment is a trimmer cap in a crystal oscillator. Been there.

John, W1TAG