Matthew Kaufman wrote: > What is the soundcard sample rate? This feels like an artifact > of sample phase vs. pulse phase to me.
There are actually two soundcards, running at 192003.8285 and 192002.1638 samples/sec, varying a little. They are on different computers. One takes an East/West signal, the other a North/South signal. Each is timed and resampled to 192000.0 based on the PPS supplied to both soundcards. The two timestamped data streams are then brought together for bearing and phase extraction. The plotted phase is actually the mean (weighted by signal strength) of the phases separately determined for each signal. Tests with a signal generator show that the signals are being correctly resampled, only a small and fairly constant phase error between the two signals. Perhaps there is some subtle aliasing between the two signals and/or soundcards. I have altered things now to only look at the signal from one antenna, one soundcard. Will know in an hour or so if this has made a difference to the slow cycle. Joe Gwinn wrote: > The centroid of pulses triggered by the leading edge of the > 1PPS pulse will vary with the width of the pulses. I see. It is a passive network but unprotected from temperature changes. It is shut in a box with 2 PCs and a bunch of other stuff. Various fans on and off. Temperature varies 26-30C in the box. I need to look at temperature, but gut feeling tells me the cycle is a little too regular and is some subtle software defect, aliasing or something. I must plot soundcard drift rate against the slow cycle, etc. I can tackle this with confidence now that I know it is not a GPS limitation. Thanks for that. -- Paul Nicholson http://abelian.org -- _______________________________________________ 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.
