Mike,

You should be able to over come the low frequency problems of 
sound cards by putting a mixer in the front of the final 
amplifier for the sound card uses a local oscillator that was 
right a the top of the sound card response and put the image 
beyond the range of the sound card. The signals will be reversed 
but fixing that with computer that run at today speed is no problem.

Or you can put the local oscillator above the low end roll of 
the response of the sound card and digitally shave off the lower 
sides band with digital filters.

Mixers like the NE 602 and it's replacement work from dc to 1 
gHz. I strongly recommend Phillips mixer chips they come out of 
the box wanting to work.

Gordon

Mike Speed wrote:
 > Okay - forget the low frequency response of my sound
 > card is poor.  *Is there any good datalogging software
 > for a sound card?*


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