[time-nuts] Fine frequency adjustment in 5370B
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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