On Wed, 30 Nov 2011 19:56:25 -0800 Peter Monta <pmo...@gmail.com> wrote:
> Hi Attila, > > > [ L1 / L2 timing differences ] > > How do dual frequency receivers deal with that? > > I've also been toying with the idea of an inexpensive dual- or > tri-band GPS SDR, especially since there are now quite a few > satellites emitting L2C, the civil L2 signal. (Though I'd still like > to try my hand at the fancy L2 semicodeless schemes.) > > I think that manufacturers calibrate out the timing differences > between channels (as well as group-delay variations within a channel). > There must be some remaining error, though, e.g. over temperature, > depending on the filter technology. So, that'd mean there would be an automatic calibration system inside the device, because i dont have any equipment with which i could calibrate delays over a temperature range. > ObTimeNuts: There's an interesting recent thesis on GPS for time and > frequency metrology: > > http://www.ptb.de/cms/fileadmin/internet/fachabteilungen/abteilung_4/4.4_zeit_und_frequenz/pdf/Feldmann_2011_Dissertation.pdf > > Section 5.1.3 has a few words on exactly this channel-filter-delay > issue. The author measures a coefficient of 20 ps per degree for a > pair of receivers. Nice disertation, but i cannot see how you come to the conclusion that this temperature coefficient is from the input RF chain. The measurement shows only a general time shift of the whole device. And the author does not draw any conclusion from it. Attila Kinali -- Why does it take years to find the answers to the questions one should have asked long ago? _______________________________________________ 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.
