A 60kHz receiver is unlikely to be useful for nanosecond timing applications. Bruce
On Wednesday, 27 April 2016 6:36 PM, Ilia Platone <i...@iliaplatone.com> wrote: Hi All, I read from an article about this receiver: C-Max CMMR-6P-60 Can it be useful? One of the places where I'll setup the telescopes will be in mount Carpegna, near where I live. There are the repetitors of television and radio over there. Can the carrier wave of such repetitors be used as clock? they will be distant 5 Km or less from the observation location. Regards, Ilia. Il 26/04/2016 23:51, Attila Kinali ha scritto: > On Wed, 27 Apr 2016 08:25:55 +1200 > Bruce Griffiths <bruce.griffi...@xtra.co.nz> wrote: > >> 1) Relative position of any pair of clocks located up to 2km apart has to be >> known to within 3cm or so. Post processing is OK, however differential Earth >> tides between the clock locations may need to be considered. > That's doable. People at ETHZ got sub cm accuracy from LEA-6T modules > with post-processing of the recorded phase data with an integration time > of several hours. Using phase data of multiple timing modules should give > relative positions with better than 1cm accuracy on these short baselines.. > I don't know how much post-processing is necessary though. Haven't looked > into the the field of RTK[1] and PPP[2] yet. Probably data from IGS[3] is > needed as well. > >> 2) The difference in the time offset between any pair of clocks located up to >> 2km apart shall not vary by more than 200ps (1ns time stamp quantisation) or >> 2ns (10ns timestamp quantisation) over an 8 hour period (at night). >> Post processing of data to fit wander etc is not practical as the SNR is too >> low to support this. > Now this is quite a bit more challenging. While i'd say 1ns should be doable > (using receivers that are calibrated against each other and using common in > view mode during post-processing of the data), i'm not so sure whether 200ps > is possible. What might work is using an LEA-M8F with it's external frequency > input, to record the phase of an stable external reference (e.g. Rb). > Averaging that over a dozen minutes or so should make it possible to > measure the phase of the reference oscillator with 200ps precision, relative > to the other stations. > > Another way would be to use L1/L2 receivers with calibrated antennas. > I know that BIPM has a GPS station that can deliver time transfer > accuracy <2ns over a distance of several 100km. It could be possible > to use such receivers with the <3km distances to deliver 10 times better, > if they are frequently calibrated (eg. every couple of days). > But of course, this makes things much more expensive. > > But all this is a wild guess. I haven't seen anything like this done. > If you want a more precise answer i would need to think about the design > of the system for some time. > > > I guess using some cable/fibre between the telescopes is out of question? > > > Attila Kinali > > [1] http://www.navipedia.net/index.php/Real_Time_Kinematics > [2] http://www.navipedia.net/index.php/Precise_Point_Positioning > [3] http://www.igs.org/ > -- Ilia Platone via Ferrara 54 47841 Cattolica (RN), Italy Cell +39 349 1075999 _______________________________________________ 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.