[time-nuts] Antique Rb Standard - Thanks, Pictures, Parts Request, Question
ed breya
eb at telight.com
Sun Apr 29 18:28:03 UTC 2012
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
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