[time-nuts] Heated crystal? & Rb tube corrosion (FE-5680A)

[Steve .]

I've been paying particular attention to the discussions involving the
FE-5680A frequency standards of recent attention. I do not have a FE-5680A
yet, but rather I am studying what is shared from the others prior to
buying. At the very least I want to know what I'm up against should I get a
DOA module.

It appears that these units use a heated crystal.(..i sure hope it's heater
and not an acoustic resonator). Has anyone performed sub 1degree c drift
testing against a known stable source? What are the performance gains by
using tighter temperature control? Also It appears that quite a few of
these have corroded Rb tube interfaces. My guess is the corrosion is a
tale-tale sign of small amounts of rb gas leakage in combination with the
raised temperatures of the tube oven?  If this is the case I suppose a
visual check of the tube interface for corrosion would yield a fair
approximation of the tube condition?

Lastly, is the Rb tube a quartz tube or is it a metal(silver
lined?)canister sealed with polymer tape?


Thanks,
Steve