[time-nuts] Counter Internal Oscillator Importance with External Reference?
phk at phk.freebsd.dk
Tue May 9 09:55:39 EDT 2017
In message <54ee7bdd-0a49-cc49-540d-2812e70dd4f3 at rubidium.dyndns.org>, Magnus Danielson writes:
>Wither it is proper side bands or other systematic noise, it is bad
It's more subtle than that, it can be things like thresholds in
the counters trigger being sensitive to the phase of the internal
clock because of (very slight) cross-talk.
I reported data on this a couple of years ago, as I recall my setup
were something like this:
House-10MHz --> HP3336C clk-in and HP5370B clk-in.
HP3336C output -> HP5370B start then 3m coax then HP5370B stop.
Measure TI(start->stop), for different settings of output phase angle on the HP3336C.
Theoretically that plot should be a flat line.
In practice it is not even close.
I think I convinced myself that the majority of the problem was trigger-noise the HP5370B,
but my notes are not accessible at this time.
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