[time-nuts] Fine frequency adjustment in 5370B

David Kirkby david.kirkby at onetel.net
Sun May 15 17:09:42 EDT 2005

John Miles wrote:
> Correct, the only adjustment on the 5370B is on the 10811 itself. 

Cheers. I thought that was the case, but confirmation is never a bad thing.

> 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.)

That's what I was intending doing, although the adjustment as far 
courser than ideal on a counter with 11 digits.

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

I don't have anything locked to GPS yet, but even when I do, it is not 
always going to be that convenient for me, so having a reasonably 
accurate timebase in the counter will be useful. Sure, putting in a 
rubidium locked to GPS would be nice, but not always practical for me.

Thanks very much John.

> -- 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
>>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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David Kirkby,

Please check out http://www.g8wrb.org/
of if you live in Essex http://www.southminster-branch-line.org.uk/

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