> -----Original Message----- > From: [email protected] [mailto:[email protected]] On > Behalf Of John Miles > Sent: Friday, August 21, 2009 11:59 AM > To: Discussion of precise time and frequency measurement > Subject: Re: [time-nuts] Using cheap sound cards for measurements > > If isolation turns out to be a problem, I imagine it would be practical to > use two separate sound cards. It may not be practical to compensate for the > frequency-dependent effects of channel leakage, but timing/rate differences > between two independent cards should be less important and/or easier to > calibrate out. Unless I'm overlooking something, ADC timing precision > and accuracy would be directly improved by the heterodyne ratio, just as > effective TIC performance is improved in a classical DMTD > configuration. >
Wouldn't the cards need to be synchronized, though? Essentially, you're still comparing the two signals with each other, just doing it in software, rather than in hardware, in the classical time interval counter scheme counting 1Hz (or 123Hz). Syncing inexpensive cards is a real chore (and the only reason to be thinking about using this in the first place is to keep the cost to a minimum, otherwise, you might as well build a special purpose little box with counters & A/Ds, and an interface) _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
