[time-nuts] Setting loop TC using thunderbolt internal data.

Magnus Danielson magnus at rubidium.dyndns.org
Fri Jan 23 21:00:29 EST 2009


Bruce Griffiths skrev:
> Tom Van Baak wrote:
>> Has anyone hacked a TBolt yet to find which internal pin has
>> a raw 1PPS from the GPS engine (as opposed to the 1PPS
>> divided down from the OCXO)?
>>
>> /tvb
>>
>>   
> Tom
> 
> The Thunderbolt manual (Page 1-1) makes it clear that there is no PPS
> output pin from the GPS receiver itself.
> There is also no internal TIC.
> The phase and frequency errors are derived from the sampled GPS signals
> without requiring an explicitly generated receiver PPS output.

The Lassen LP receiver *seems* to be using the same correlator and 
processor chip and lacks the PPS, so it kind of make sense.

The divided down signal does not seem to lock up the GPS chains 
oscillators (at least not when not seeing birds) but it could be that 
the signal is used as a time-reference so that the correlator chips 
internal timing can be coupled to the PPS state.

Cheers,
Magnus




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