[time-nuts] RFDO - Experience and questions

David davidwhess at gmail.com
Sun Mar 5 11:35:09 EST 2017


If the modulation is phased locked to the carrier which is common,
then that suggests two other ways to extract the timing from the
carrier without interference from the modulation.

1. Integrate the phase comparison over a whole number of modulation
cycles; the modulation will then cancel out.  This could be seen as
using a sin(x)/x frequency response with the nulls aligned to remove
just the modulation components of the signal.

2. Gate the phase comparison for periods where the modulation is not
occurring.

On Sun, 5 Mar 2017 11:54:56 +0100, you wrote:

>I have been working for a "while"
 on a reference oscillator disciplined by an RF signal (162khz), Cs stabilized, but phase modulated with time coding information. The phase modulation is quite significant : +/-1rad 10Hz triangular shape, leading to a frequency shift of +/- 20PI (+/-6,3Hz). Extracting the base signal was quite an interesting challenge
 I tried many options (and even a bit more
) but it was - and is still - fun...
>
>...
>
>My questions to the respected audience:
>- Can I get any better? 
>- Have I reached the limit of what the RF signal can provide? 
>(with all the perturbations encountered on the path from the transmitter to my antenna...)  
>- Am I limited by the local oscillator? 
>- Or the measurement gear?
>- Or anything else
?  
>
>Thanks very much for your feedback,
>
>Gilles. 



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