Thank you Ole Juerg and I spend most our time on frequency,control and measuring. We also see 2 E-12 frequency using GPS and blame the Ionosphere. Which brings up the Question does the way you use the OEMV-3 in your experiment use L1 L2 compensation and where can I buy one? Looked for hours last night. Second have you looked at the Furuno GT-87 we bought the latest version which claims 1.7 nsec saw tooth . Buerklin in Germany sells them, we bought some and I expect boards tomorrow. If you want some boards I mail them to you. Bert In a message dated 5/14/2018 4:16:03 PM Eastern Standard Time, opronnin...@gmail.com writes:
Hi Perhaps this is of interest to some. I finally got around to doing an experiment I've been mulling over for some time. In short, I use a Novatel OEMV-3 GPS receiver, clocked by an Oscilloquartz 8600 BVA, process the observations with RTKLib and real time corrections from igs - and use the resulting clock solutions as inputs to a software PLL that sets the EFC on the BVA via a Keysight 33510B function generator set to DC. A bit of a contraption, but it works surprisingly well (or perhaps I should say it surprisingly works!) I measured the GPSDO using a TimePod and my maser. There is *much* room for improvement, and probably too little data, but I thought the preliminary results worthy of a post: The ADEV is <5e-13 on the "hump". It passes through to e-14 territory around 6-7000 seconds, at least in this dataset. The TDEV flattens out around 2e-10 at 2000 seconds or so (a little wiggle on the end, but I choose to ignore that and blame it on not enough data). If the masks in TimeLab are to be trusted, it is very close to a 5071A high performance option in this region (400 to 10000 seconds), and of course much better at lower taus. The frequency accuracy stays within 2-3e-12, and the phase rarely wanders off more than 1 ns. I have pretty much everything to learn about tuning GPSDO's, but I think it shows that the approach is viable. I ofcourse also need to collect a *lot* more data, get a proper DAC in place and so forth, but still. To get some sort of baseline, I also processed in real time using the same correction stream observations from a Trimble NetRS clocked by the hydrogen maser (sadly not at the same time) - the resulting curves should pretty accurately show the limits of the approach - at least using the corrections I was using (CLK93; there are many to chose from, and frankly I don't know which would be best for something like this. ) The .tim-files are here: http://www.efos3.com/downloads/GPSDO_14.05.18.zip As a final thought - this setup can be made "self documenting": log the observations to RINEX-files, and solve with PPP and IGS Rapid or other corrections. The resulting phase record should be good to at least low e-15 from what I understand (and observe). Ole _______________________________________________ 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.
