I've been building my DIY counter, with GPSDO ref clk. I do not have rubidium or cesium gear handy.
Are there any basic measurements one can make in order to characterize such a DIY gear without having something better to compare?
For example, the first thing came to my mind was to measure its own ref clock.
Getting a nice straight adev line in TimeLab.
Could the experts here identify some issues, the counter's and/or gpsdo's parameters (ie. its own jitter/noise background) out of such data?
For the shorter time scales one could check against a good quality quartz oscillator (e.g. oven ). For the short times, up to a few seconds the fixed oscillator should be better than the GPSDO. So this should give some check of the counter artifacts (e.g. jitter, interpolator errors) and the PLL in the GPSDO. For checking the slower part is would need a really good second clock.
For the shorter time scales one could check against a good quality quartz oscillator (e.g. oven ). For the short times, up to a few seconds the fixed oscillator should be better than the GPSDO. So this should give some check of the counter artifacts (e.g. jitter, interpolator errors) and the PLL in the GPSDO...
tau[s] MADEV[best]
0.01 4.8E-8
0.04 5.5E-9
0.1 1.3E-9
0.4 2.8E-10
1.0 2.2E-10
2.0 2.0E-10
3.0 2.0E-10
4.0 2.0E-10
The first thing I like to ask you, imo, is what resolution your counter gives? I can guess from the charts you have that it is possible to get ADEVs at 1 sec of about 2E-10 (10 digits) and from my Arduino based counter with 1nS that gives 8E-10 ADEV at 1secs in best case and my TAPR TICC that gives 7E-11 with about 55ns resolution I would guess your resolution is in the range 100pS?? ..
So the first question what resolution do you have and the second could you give both ADEV and MDEV charts?
The GPS constellation repeats twice a day and transmission conditions roughly repeat every day.
If I did not have anything better, then to start I would design the GPSDO for stability of the voltage control input to the VCXO and monitor that for days to weeks to at least get an idea of what is going on. The GPS constellation repeats twice a day and transmission conditions roughly repeat every day.
The GPS constellation repeats twice a day and transmission conditions roughly repeat every day.
Although technically the constellation repeats twice a day, in practice it does not. If a sat went directly overhead on the first pass, on the second pass it would have a fairly low and shorter visibility.
The GPS constellation repeats twice a day and transmission conditions roughly repeat every day.
Although technically the constellation repeats twice a day, in practice it does not. If a sat went directly overhead on the first pass, on the second pass it would have a fairly low and shorter visibility.
Thanks, the guys in Braunschweig have got the gear (I need) handy..
@Lars, is there a chance to see a measurement from TAPR-TICC similar to mine above to make, say, 1000 measurements of its own 100ns ref clock period in ps, such I can see the 7200's results distribution?