[time-nuts] Re: Some assistance with Ball-Efratom FRK-L Rb Osc. Needed

[ed breya]

If you look at the schematics of the C-field adjustment circuits, you'll 
find where the tweaking is available for fine tuning the Rb system. I 
think that's the only "frequency adjustment" spot to worry about. The 
other is the tweak for the crystal oscillator to accommodate long term 
drift there, if its tuning range hits a limit. This an internal, seldom 
needed adjustment, so the C-field is likely the only one that would be 
useful externally, to (very) fine tune the output frequency. I have some 
similar M-100 units, which have access to the C-field pot through a hole 
in the back end heat sink and case. An external adjustment port would be 
either a substitute for the internal pot, or something to add to or 
subtract some current from the C-field coil, that's mostly controlled by 
the internal pot.

So, look for an internal pot. If there is one, then the external stuff 
likely just modifies what it does. If there isn't one at all, then the 
external circuit may have to provide the proper current, so it may be a 
little more complicated. It could also be that the C-field is set up to 
some nominal value, with fixed resistors, without any internal pot, and 
an external one just moves it around a bit.

If you just run it, and it locks, it should be good to go, and you can 
figure out these fine tuning issues later.

Ed