>Isn't +/-100ppm +/-0.01Hz at 1000Hz?

100 ppm is 0.0001.  0.0001*1000 Hz =3D 0.1 Hz

The other issue with some sound cards has to do with the sample rate
not being uniform due to hardware limitations (poor design).  That=20
would show up as noise on the output in this case.  There are DSP-type=20
radio receivers out there that use sound cards for digitization, but=20
they choose their sound cards carefully.

Despite all that, I'll bet you can demodulate something that looks
very like a seismic signal with any old sound card and some=20
effort. =20

Jack


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