1 Hz in 10Mhz is about the same ratio as 5mHz in 64Khz. This would make sense if the Clock for the A/D is divided off the same TXCO.
Or am I missing something. The reason I jumped in, in a recent frequency measuring contest the winner was using that interpolation for his results. Regards Randall ZL2RJP -----Original Message----- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of David McClain Sent: Wednesday, 13 October 2010 2:18 p.m. To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Question about SoundCard stability? Ahh.. so... Now since my TCXO is drifting to and fro by 1-2 Hz over the period of 45 minutes, why don't I see similar drift in the 100 Hz audio signal, down around 5 mHz amplitude? This happens to be about the same size at the FFT bins. So I am led to conclude that "interpolated" peak frequencies are a bogus technique, and you can only truly count on variations on the order of the FFT cell size as being measurable... Dr. David McClain Chief Technical Officer Refined Audiometrics Laboratory 4391 N. Camino Ferreo Tucson, AZ 85750 email: d...@refined-audiometrics.com phone: 1.520.390.3995 web: http://refined-audiometrics.com On Oct 12, 2010, at 17:57, Bob Camp wrote: > Hi > > Yes it is a reasonable expectation as long as you don't have a lot > of drafts. A good TCXO can get down to sub 0.1 ppb over that period. > > Bob > > > On Oct 12, 2010, at 8:21 PM, David McClain wrote: > >> Okay, perhaps I should rephrase the question... Is is reasonable >> to expect a TCXO to perform at 4e-9 over the FFT window period of >> about 87 sec? I can only imagine that the enormous (87 s) >> averaging period is making my measurements look so good. >> >> Dr. David McClain >> Chief Technical Officer >> Refined Audiometrics Laboratory >> 4391 N. Camino Ferreo >> Tucson, AZ 85750 >> >> email: d...@refined-audiometrics.com >> phone: 1.520.390.3995 >> web: http://refined-audiometrics.com >> >> >> >> _______________________________________________ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/ >> listinfo/time-nuts >> and follow the instructions there. > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/ > time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
