James Moritz schrieb:
The obvious problem is how to determine the soundcard error, if
you don't have a accurate audio frequency source. I used the
reference output of my synthesiser divided doown to 1kHz (and
filtered; a fairly clean sine wave seemed to be neccessary to avoid
aliasing problems with the soundcard). You could use the RX audio
out, but only if you knew what the RX frequency error was to within
a small fraction of a Hz.
Cheers, Jim Moritz
73 de M0BMU
Hi Jim and all,
audio qrg source out of ur old PC does it too. take Rik`s QRS-progr, switch
setup/sound/dfcw/enable/fill in the qrg u want in both dash- and dot-window the
same qrg.
hardware: take the speaker output (kill the speaker as Rik suggested), form the
needle-waves into sinus-waves (I took out of my junk-box a pot-core 330mH,
1,8mikroF and 100nF for c1 and c2 of a Pi-Filter for transforming 10ohm to abt
6kohm)and measure the qrg. Taking 1000Hz out of my junk-pc (486/66Mhz with the
motherboard crystal tempcompensated)in the above described manner the counter
shows 1000.0706Hz to 1000.1804Hz constance over 4 hours.
regards
Uwe/dj8wx
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