[time-nuts] RFDO - Experience and questions

paul swed paulswedb at gmail.com
Sun Mar 5 16:32:03 EST 2017

Gilles I should have mentioned.
I use eLoran at 100 KHz in the US and am 400 miles from the transmitter.
Measuring Cesium references I typically run down in the 5 e-12th.
I see various noise at that level that says thats about the limit without
some smarter filtering, tracking and plotting.
The comparison units are austron 2100 series. The Cesium's are HP5061A's.
Very interested in what you are doing.

On Sun, Mar 5, 2017 at 11:35 AM, David <davidwhess at gmail.com> wrote:

> 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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