[time-nuts] Antique Rb Standard - Thanks, Pictures, Parts Request, Question

[ed breya]

Yes, very nice pictures. That thing is really built and looks like it 
should be easy to work on and experiment with.

I still have to say that I doubt the cavity is off-tune unless 
something serious happened to it mechanically. Is it even adjustable? 
If so, maybe someone previously tried to adjust it and messed up. If 
not, or it appears original, then I think any mistuning will be in 
the multiplier instead.

You can sweep the cavity by placing coupling loops in there, and then 
see what happens as you go say +/- 100 MHz around the desired center, 
and then at narrower sweeps. You should get an observable peak at or 
near the right frequency, and it should be broad enough to include 
the ideal Rb frequency. When the excitation lamp is on and the cell 
has some light going through, there should be some absorption, and 
the cavity Q may decrease a bit, but I doubt it will have much 
effect. You can try this by sweeping with everything off, and then 
with the lamp on to see if it's noticeable.

Also, as someone else mentioned, it's good to see fully-utilized 
bench space in the background - plenty of stuff everywhere, at your 
fingertips. I especially liked the open-sided desktop PC. All of my 
garage PCs are just like that (I don't even know if I can find the 
covers) - it gives better cooling, is easy to modify and experiment 
with, and provides some handy storage space that otherwise would be wasted.

Ed