> Le 29 juin 2016 à 22:18, Poul-Henning Kamp <[email protected]> a écrit : > > -------- > In message <[email protected]>, Hal > Mu > rray writes: > >>> At one point they were looking into making a GPS time receiver where the >>> cable length calibration would be built-in. >> >> How would you do that? > > TDR ? > > If it wasn't behind a choke, the inrush current to the antenna > preamp power filtering capacitor could be measured, but the choke > ruins that. > > The trouble is how to do it without frying the antenna preamp... > > > Seriously... > > GPS antennas and receivers are cheap, I would just use two GPS antennas > with a known difference in cable-length. > Sounds simple, but even after a days reflection I don’t see how you find the complete path delay. You would get the cable delay (OPs concern) provided they were the same antenna/cable type combinations, but not delay induced by the antenna electronics. From another post that delay seems to be non-negligable. I find it curious that antenna manafacturers don’t seem to give this parameter. I looked at some datasheets on Trimble and Leica sites but they don’t have it. As for me, I measure cable delay by injecting a 1PPS into it through a T and for the RG174 attached to the patch antennas, just sacrificed one by cutting the head off and measuring that.
> -- > Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 > [email protected] | TCP/IP since RFC 956 > FreeBSD committer | BSD since 4.3-tahoe > Never attribute to malice what can adequately be explained by incompetence. > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. "The power of accurate observation is commonly called cynicism by those who have not got it. » George Bernard Shaw _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
