[time-nuts] FTS125 GPS Module

[SAIDJACK at aol.com]

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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