[time-nuts] FTS125 GPS Module
SAIDJACK at aol.com
SAIDJACK at aol.com
Thu Jun 28 18:25:39 UTC 2012
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,
expertengineer at live.co.uk 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
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