Hi Best guess is that the codec in the Flex runs on the same TCXO as the rest of the radio.
Bob On Oct 12, 2010, at 7:48 PM, David McClain wrote: > Hi, > > I have a Flex-3000 receiver, running freely on its internal TCXO (0.1 ppm). I > have been recording the reported deviations in the measurements of the 100 Hz > sizeband of 10 MHz WWV all day long. I do this in AM detection mode, to > remove any variations due to the wander in the radio LO. Recording from the > 48 kHz audio stream and into SpectrumLab for analysis. > > After taking out the measured frequency error in the "soundcard" (which I > believe is the Flex Radio internal CODEC), of 17.5 mHz, I'm seeing frequency > deviations of 0.2 mHz RMS, and +/- 1 mHz p-p, with no measurable long term > drift. The FFT uses a bin size of 11.44 mHz. SpectrumLab interpolates to the > peak assuming high SNR and a Hann window, with no nearby interference. > > This implies that my "soundcard" is giving me a stability of 0.004 ppm, or > around 10^-9. How can this be? I already know that the TCXO wanders about by > as much as +/- 1 Hz at 10 MHz due to temperature variations in the room. > (10^-7). If that TCXO were used to derive the soundcard (CODEC) clock then I > should be seeing variations of 25x larger. And I can assure you the CODEC is > *not* being driven by an OCXO or GPSDO of any kind. > > Anyone? > > Dr. David McClain, N7AIG > Chief Technical Officer > Refined Audiometrics Laboratory > 4391 N. Camino Ferreo > Tucson, AZ 85750 > > email: [email protected] > phone: 1.520.390.3995 > web: http://refined-audiometrics.com > > > > _______________________________________________ > 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. _______________________________________________ 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.
