Hi > On Jun 16, 2017, at 6:21 PM, Attila Kinali <att...@kinali.ch> wrote: > > On Fri, 16 Jun 2017 17:46:45 -0400 > Bob kb8tq <kb...@n1k.org> wrote: > >> A far more common approach is to let the two oscillators free run and to >> record something like a local broadcast station. >> You then post process all of the data to give you the phase accuracy. One of >> several gotcha’s is the stability of any >> radio link at the level you are looking for. > > Well, we still don't know what the requirements are.
…. well, we do. A requirement of 0.1 degree at 100 MHz was stated earlier on. That’s where the ps stuff comes in. Bob > Though I doubt that a GPSDO cannot deliver the needed stability. > Unless the goal is to build a multi-static radar that can locate > a plane down to sub-cm range, ps level stabilty is not required. > Even something as demanding as VLBI is in the couple ns range. > (But they measure over long intervals (hours) which puts higher > demands on the local oscillator) > > Another reference value: Time transfer using calibrated GPS receivers > achieves an absolute accuracy of about 1-2ns(RMS) over base lines of > several 10km with single frequency receivers. Dual frequency receivers > have been reported to do <200ps[1] over 400km (TDEV <60ps up to 5days). > > > Attila Kinali > > [1] "Comparing a GPS time link calibration with an optical fibre > self-calibration with 200ps accuracy", by Jlang et al 2015 > http://dx.doi.org/10.1088/0026-1394/52/2/384 > > -- > You know, the very powerful and the very stupid have one thing in common. > They don't alters their views to fit the facts, they alter the facts to > fit the views, which can be uncomfortable if you happen to be one of the > facts that needs altering. -- The Doctor > _______________________________________________ > 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.