Date: Mon, 30 Jan 2012 22:42:40 -0500
To: rsgb_lf_group@blacksheep.org
From: Bill de Carle <ve2iq@magma.ca>
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Subject: LF: WOLF Monkey Business
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I have here two versions of the original WOLF command-line program: 
0.51 and 0.61 - apparently there is also a version 0.62 which is used 
by the GUI program.

I wanted to duplicate what Stefan did using the GUI version: generate 
a signal on 8970 Hz using 24000 s/s.  It *seemed* to work OK but when 
I examined the sound card output signal with Cool Edit, the frequency 
was way low - about 8241 Hz instead of 8970.  So I went back to the 
original command line programs.  I found that versions 0.51 and 0.61 
apparently worked, generating 2,304,000 audio samples (exactly 96 
seconds at 24000 s/s) to a file called  WOLFX.WAV.  Unfortunately the 
samplerate in the .wav file header was coded as 8000 s/s, which means 
if we played it back it would run for 288 seconds and the audio 
carrier frequency would appear at 2990 Hz.  So I went in and manually 
changed the s/s field in the wav header to 24000 s/s.  Then the file 
worked OK.  I was able to decode the message by mixing the 8970 Hz 
down to 800 Hz and decimating the sample rate to 8000 s/s.  Turning 
again to the GUI version, I asked it to encode a .wav file at 24000 
s/s with a carrier freq of 8970 Hz.  It reported version 0.62 and 
everything OK.  However, when I examined the WOLFX.WAV file so 
created, its .wav header said the samplerate was 22050 s/s instead of 
24000 s/s!  That explains why the real-time GUI uutput seemed low in 
frequency: 8970 * 22050 / 24000 = 8241.1875 Hz.  The upshot is we 
need to manually check the wav header and set the s/s field to 24000 
instead of whatever else it might say.  And furthermore, don't trust 
the real-time Tx soundcard output signal frequency with the GUI 
version, especially when using odd-ball sample rates and high output 
frequencies which may never have been tested.  Be aware that WOLF 
generates envelope-shaped audio, so it might be more difficult to 
convert it to a clean square wave to drive a Tx, especially near the 
phase transitions where the amplitude drops down to zero.

73,
Bill VE2IQ