[time-nuts] Hydrogen maser frequency jumps

Magnus Danielson magnus at rubidium.dyndns.org
Sat Dec 5 07:25:06 EST 2015


Jim,

On 12/05/2015 11:45 AM, Poul-Henning Kamp wrote:
> --------
> In message <CALH-g5bQ-muUQP=HpXR6wNciNqBwwOFJ0XOb3q15wYOEwOXmxg at mail.gmail.com>
> , Jim Palfreyman writes:
>
>> The weird thing is that the jump is ~0.7ns and that 1/0.7E-9 is close-ish
>> to 1420.4MHz which is the hydrogen line. Too much of a coincidence for me.
>
> Is there a direct digital divider chain to the PLL which steers the
> 5Mhz OCXO ?
>
> If so the obvious thing to look at is a weak input signal on the input
> side of that divider.
>

Indeed, as it does cycle-skipping, so it seems you miss detecting one. 
You could get similar behavior if you ripple ahead a cycle every once in 
a while.

I've been fighting cycle-skipping issues before, but not on H-masers. 
Check your signal level is a good start.

Cheers,
Magnus



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