Hi Andrey,
this has been mentioned before - have you checked your ADC samplerate? See
http://www.wsprnet.org/drupal/node/339. If tx and rx
samplerate deviated by say only 0.3% (ie. 36 Hz from 12 kHz), the bit timing would have shifted by half a symbol duration at the
end
of the 162 bit message. I started having doubts about my own DAC rate when
Graham reported negative decoding, but the TX audio
frequency seems to be correct to within a fraction of a Hz. You could roughly check the rx samplerate by injecting a known 1.5
kHz
tone and use WSPR spectrogram which resolves ~ 0.1%. Regarding other digital modes, I recall that samplerate was very critical
for
WOLF which relies on a coherent bit frame over a long integration period. On
the other hand, it's not much of an issue for PSK31
which is "freerunning" only for a few symbols.
The maximum tolerable PC clock error between tx and rx seems to be 2.2 seconds. This was the last displayed dt offset before I
lost
track of Jim's consistent signal the other morning. My PC clock is slightly
slow and would need resetting more often. But you
mentioned you have that under tight control.
The WSPR program does not seem to be disturbed or overloaded by strong out-of
band signals. Inserting a 200 Hz filter before the
decoder made no difference at all, even though the total audio power was reduced by 20 or 30 dB. I also did not see any
degradation
when I used very low audio levels. The WSPR spectrogram seems to have a display
leveling similar to the Argo AGC option, as the
colours do not change when the audio gain is varied.
Best wishes
Markus, DF6NM
----- Original Message -----
From: "Andrey rn3agc" <[email protected]>
To: <[email protected]>
Sent: Friday, January 16, 2009 8:56 PM
Subject: Re: LF: WSPR does not work
Hello Johan, James, LF,
Many thanks for the help! Yesterday WSPR-signal DF6NM
passed here from time to time much more strongly, than the day
before yesterday. But decoding still was not. I have installed WSJT7.
If again the result is negative, the problem most likely in a sound card
means. Though to this case without problems decoded any amateur
digital protocols.
73
Andrey RN3AGC in KO85SV
