touched) It is easy to say that: 1) the lower the reading, the better the frequency source for tau = 1sec 2) compact Rubidium is worse than OCXO in short time stability. 3) the ADEV of the SR620 (if it applies) is better than any of the above readings 4) the ADEV of the SR620 is perhaps not too much better than the lowest reading of above, 1.0E-11 is my estimate

. > > AFAIK, Ashtec's patented "Z-code" receivers generate a hardware > > estimate of this code and (nearly) coherently demodulate the signal. > > Other brands have similar tricks up their sleeve. > >The Y-code is the P-code xored with the A-code (sometimes also referred to >as the W-code). The A-code is indeed ~500 kbis/sec.

The L2 P-channel is then decoded by the W-code estimate and P-code tracking is acheived by using a delayed variant of the P-code.

. > > So I am anxious to use the AlaVar software and the toys I have listed > above to do the following: > > 1) select the best OCXO to be the basis of my GPS disciplined frequency > standard > 2) find the best placement for the GPS antenna (the one that gives the > most stable GPS signal) > 3) fine tune the phase lock parameters and estimate the quality

> > So I am anxious to use the AlaVar software and the toys I have listed > above to do the following: > > 1) select the best OCXO to be the basis of my GPS disciplined frequency > standard > 2) find the best placement for the GPS antenna (the one that gives the > most stable GPS signal) > 3) fine tune the phase lock parameters and estimate the quality

But you have to use a barometer (Fortin pattern) to find the atmospheric pressure, correct for the density of mercury, correct for the expansion of the scale, get an estimate for local gravity from the Geoid, apply an altitude correction.

Measuring the round trip time, and using that to estimate the latency, etc., accounting for the human reaction time, etc.) Roads in rural areas often follow the section or township boundaries, and where the discontinuity is, the road has one too. > > The lines on the maps are often quite non-square.

Some estimates for the effect of multipath on code phase receivers can be found: http://bbcr.uwaterloo.ca/~wzhuang/papers/iee95_gps.pdf http://bbcr.uwaterloo.ca/%7Ewzhuang/papers/iee95_gps.pdf Since the better timing receivers use carrier phase smoothing of the code phase timing, both the carrier phase and code phase performance of the antenna are important

Also consider that the Allan variance estimator will loose statistical resolution for longer taus as it's effective degrees of freedom becomes less and less. I hope you have got some useful hints. Let me know of your progress. Cheers, Magnus

NTP and various related kernel PPS code attempt to use an accurate stream of 1 PPS (or whatever) interrupts from a highly stable and accurate external ticker somewhere to measure and predict the behavior of the drifting unstable CPU clock so it is possible to compute a running estimate of offset between the time of day counter on the CPU (and the real time