[time-nuts] GLONASS receiver

Bob Camp lists at rtty.us
Sun Aug 5 19:27:20 EDT 2012


Hi

If the OCXO is off by 200 ppb, it will slip time by 200 ns per second. 

It will be off by a *lot* more than 200 ns at the end of a year. Compared to the spec's on a cell tower OCXO, 200 ppb per year isn't very good...

Bob


On Aug 5, 2012, at 7:23 PM, mike cook <mc235960 at gmail.com> wrote:

> 
> Le 06/08/2012 00:01, Bob Camp a écrit :
>> Hi
>> 
>> The part at the link does not appear to have a holdover specification. You probably would do better with a TBolt off of eBay.
> Agreed.
> I took a look at the Axtal AXIOM40 data sheet and they are quoting 200 ppb per YEAR aging.. That's not bad; so if the device is only affected by that in holdover, it's only 200ns slow out at the end of a year ... I doubt that my T-Bolt could do as well. So as to providing a stable frequency it looks fine. HOWEVER that particular device has1PPS on the DCD line FROM the GPS receiver and not disciplined by the OCXO, so the advantage is lost and the PPS will drift at the receivers onboard crystal aging rate while not getting updates from GPS.  So it's not a good choice. Better to get a device with PPS disciplined directly by the main oscillator and aligned to UTC when  the signal is available as in a T-Bolt.
> 
> -- 
> Les chiens aboient, et la caravane passe.
> 
> 
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