>other GPS receivers have the same exact problems when left in >holdover for hours or more
Are you sure? Never seen that behavior on a Trimble, Motorola/iLotus, uBlox, Sanav or SkyTraq receiver, only on NavSync. The locking algorithm of the FTS250 (and maybe the FTS125 too) is a National LMX series PLL chip (I can't remember the exact part number, have to check with the FTS250 COO we have). On Thu, Jun 28, 2012 at 8:25 PM, <[email protected]> wrote: > Hello Martyn, > > I evaluated the FTS125 TCXO module (FTS250 model) as well, and found it to > have massively more phase noise and spurs than its specification, and to > have a huge frequency jump of 1.2E-7 (1.2Hz) when coming out of just a > couple of minutes of holdover. > > See the attached test results. I did not test the unit for very long > holdover, but other GPS receivers have the same exact problems when left in > holdover for hours or more, and a good GPSDO will address that issue in > it's > firmware so as to make it transparent to the user. > > Of course the FTS125 doesn't have firmware other than what is in its GPS > receiver, as its locking algorithm is inside a PLD. > > bye, > Said > > > In a message dated 6/28/2012 07:45:23 Pacific Daylight Time, > [email protected] writes: > > Hello, > > Has anyone had a play with the FTS125 GPS reference from Connor Winfield. > > I have one question on it. > > I notice if the unit is locked to GPS and the antenna is removed, the unit > goes to holdover which is correct. > > If the antenna is replaced quickly (within minutes) then the module > changes back from holdover to GPS lock, which is what I would expect. > > However, if the antenna is left out for hours, then re-connected, the unit > never goes back to GPS locked and remains in holdover, this despite 8 or > more satellites being received. > > I have tested multiple boards and they all do this. This is on the CTV > TXCO version. I haven't tested the COO version yet. > > Anyone else seen this. Any fax? > > Best Regards > > Martyn > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions > > _______________________________________________ > 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. > _______________________________________________ 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.
