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VE2HAR > MT63 12.03.05 02:53l 64 Lines 2274 Bytes #-7341 (0) @ WW
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Subj: [MT63] Sound Card Calibration
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Forgive the crossposting to four groups, but I thought that some of you may
benefit from my experience in setting up PCs for sound card modes.
I am trying to set up two computers to work with a number of modes including
MT63, Olivia, and SCAMP. One computer worked OK on MT63 and marginally on
Olivia, the other could not receive MT63 or Olivia modes at all!
I found that this was due to differences in sound card clock speeds. The
nominal clock speed is 11025 Hz but each card varies from that. MixW has a
procedure for correcting for this variation by tuning in WWV and examining
the tones with SSTV mode. After performing this adjustment, MT63 worked
perfectly.
OliviaAid has a user defined sound card setting for compensating for this
variation. To find the right setting you need to use a test signal and
adjust the setting for maximum S/N ratio. The formula is: (Actual clk
spd/11025)*8000 = sound card setting. This is what I ended up with:
Sound Card MixW (ppm) Olivia Actual Clk (Hz)
Sound Blaster 24bit External -2106 7977 10993
Sound Blaster MP3+ External 6983 8098 11160
SoundMax Digital Audio Internal 6843 8100 11163
Question for the Oliviadata group...Would data decoding improve if we could
correct the Paclink software timing for these variations in sound card clock
speeds? Rick, would it be possible to have a sound card setup in the
software with a correction entry?
Aloha & 73,
Steve - WH6N
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