[time-nuts] Fine frequency adjustment in 5370B

John Miles jmiles at pop.net
Sun May 15 15:56:58 EDT 2005

Correct, the only adjustment on the 5370B is on the 10811 itself.  The best
way to set it is to note the deviation after a long warmup with the counter
covers in place, then take everything apart and adjust the 10811 to remove
the same amount of deviation.  (If you set it to 10.000000000 MHz with the
covers off, it won't be there under typical operating conditions.)

I don't bother keeping mine calibrated, since everything runs off GPS.

-- john KE5FX

> The frequency of the oscillator in my 5370B seems to be a little off -
> at least according to my Standford PRS10 rubidium. Although the latter
> has not been calibrated recently, I suspect the rubidium is more
> accurate than the 10811-60111 in the 5370B, so was intending changing
> the latter to that of the rubidium.
> Although when one removes the top cover of the 5370B, the 10811-60111
> can be seen with its adjustment control, I believe this is a course
> adjustment (18 turns is supposed to move it +/- 10Hz, at least on the
> 10811A).
> I know you can trim these oscillators with a fine control, using the EFC
> voltage. Is anyone aware of whether this is possible on the 5370B or not?
> I have the service manual, and so no mention of it. Neither can I see
> any control, so I guess the answer is probably no. But the PCB the
> oscillator plugs into hidden beneath some shielding, so I am not 100%
> sure there is no pot.

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