[time-nuts] GPS Locked and Unlocked Performance Comparison

[SAIDJACK at aol.com]

Hello Tom,
 
yikes, that does sound like a project indeed.
 
Long Term holdover design in a GPSDO is a real challenge, and  even the older 
specs (CDMA etc) are quite hard to achieve. This is where a  Rubidium/Cs 
really has a huge advantage over any Crystal design.
 
Another problem is the very large spread unit-to-unit for long term  
holdover. I have seen the same OCXO model come from the same assembly  batch, and have 
a spread of 3x or more on the 24 hour holdover performance,  especially when 
aged less than 1 - 2 months.
 
Of course we are lucky today that a good GPS signal is available  most of the 
time, and a 24 hour hold-over capability is not a critical  issue for most 
hobbyists.
 
bye,
Said
 
 
In a message dated 2/12/2008 16:56:11 Pacific Standard Time,  
tvb at LeapSecond.com writes:

Anyway,  once I collect enough data, yes, adding a holdover
test is the next thing.  Several of these GPSDO have such low
drift as it is that it could take a  week to accurately measure  it.





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