[time-nuts] Re: FS740 Thoughts?

[Dana Whitlow]

Bob, I seem to remember reading in the manual on the PRS-10 where they
expounded
at length about how they took great pains to make the unit work well with
typical noisy
GPS PPS input.

I'm using a CNS Clock II as my primary GPSDO, checking phase slippage with
respect
to my PRS-10 to make decisions about when (or when not) to manually tweak
the PRS-10.
The CNS seems awfully noisy to me, even though the mfr says that it has
strong hanging
bridge correction.  I run the two 10 MHz signals through a quadrature
demodulator whose
I & Q outputs go into a 2-channel DSO running in extremely low "roll
mode".  I take a glance
at it several times per day, with each glance showing me the most recent
~4-hour history.
When I do tweak, I strive to set the PRS-10 about 1E-11 low in frequency,
which yields a
couple of months of hands-off operation before it drifts to 1E-11 on the
high side.  For
now, that has to suffice.  But I'd rather not have to pay so much attention
to it, which is
why I dream about buying a new PRS-10 with PPS locking capability.

Dana


On Thu, Nov 18, 2021 at 8:47 AM Poul-Henning Kamp <phk at phk.freebsd.dk>
wrote:

> --------
> Bob kb8tq writes:
>
> > The 'filter' in the PRS-10 is not really set up for a GPS sort of signal.
>
> It is particularly bad at handling GPS's because of the "hanging bridge"
> phenomena, and the better the GPS, the worse the result...
>
> I tried injecting the "negative sawtooth" via the serial port to my
> PRS10 but firmware features/bugs prevented that.
>
> The offset could only be changed permanently in the saved configuration,
> you could not change the running value on a second to second basis.
>
> --
> Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
> phk at FreeBSD.ORG         | TCP/IP since RFC 956
> FreeBSD committer       | BSD since 4.3-tahoe
> Never attribute to malice what can adequately be explained by incompetence.
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