[time-nuts] Synchronisizing a 100MHz TCXO with Tbold, pse help

Christian Vogel vogelchr at vogel.cx
Mon Sep 19 13:57:14 UTC 2011

Hi Tom,

> Would it be possible for your application to let the 100 MHz
> TCXO free-run? Then you could use one or two of the ADC
> channels to sample the TBolt 10 MHz and 1PPS leaving all
> the rest of the channels to do real work.
> This would then give you all the information you need to apply
> phase adjustments to your ADC readings as an after-the-fact
> software correction. Essentially you get all the benefits of GPS
> time tagging and accurate reference frequency along with the
> low jitter of your TCXO but without any of the additive noise of
> a hardware PLL.

but of course: Whatever algorithms you put into your after-the-fact
software correction will have an influence similar to a hardware PLL.

{With the added benefit that you can improve your code at your
leisure and re-iterate without having to repeat your data recording.}

If one doesn't want to sacrifice an ADC channel to sample the reference,
I'd suggest going Chuck's route, divide the 100 MHz down to 10 and let
the thunderbolt discipline the 100 MHz TCXO.

But when business gets serious, you can break the loop and put the
Thunderbolt into holdover manually. It will then keep the control input
of the 100 MHz stable but will still measure the phase and frequency
offset with respect to GPS time. You could then use the data recorded
 from the thunderbolt to do phase corrections on your sampled data as


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