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

Magnus Danielson magnus at rubidium.dyndns.org
Wed Jan 21 08:38:29 UTC 2009


Tom,

Tom Van Baak skrev:
> Ah, OK. So you keep the antenna connected and you keep the
> GPS receiver in position hold mode, still receiving fixes.
> 
> All you're doing is disabling the software disciplining algorithm.
> That sounds like a good test. Let me try this too and see if I
> agree with your conclusions.

We discussed this a little while back. I proposed a three-cornered hat 
using two receivers and one counter... as the Thunderbolts has a builtin 
TIC to GPS which can be logged. We also discussed just running a single 
Thunderbolt in holdover. Others had already tried that approach. Bruce 
and I discussed to some degree the effect of steering on the result.

> I'll try to simultaneously measure the 1PPS or 10 MHz outputs
> as you suggest.
> 
> 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)?

Hmm... I have not even "repaired" (in the sense, that they are broken 
until opened and "repaired", i.e. just looking under the hood for sake 
of curiosity). any of mine...

Cheers,
Magnus



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