[time-nuts] Difference between Datum 4065, A, B & C Cesium T&F standard?

[Tom Van Baak]

> A two way RS-232 interface allows not only reading a bunch of operational 
> parameters but also setting a number of things.  This could be GPS disciplined 
> using RS-232 to tweak the frequency.  Maybe that's how the Frequency Offset 
> came to be non zero.

Brooke,

Yeah, that offset is pretty high. Someone might have played
with it, or used the 4065B as an offset generator, or maybe
deliberately set it a bit off-frequency to improve time-interval
averaging statistics. Or like you said, used the offset to make
small periodic phase adjustments as part of a CsGPSDO.

When you get a Cs standard that is inherently stable down in
the -13's or -14's you can also use the programmed frequency
offset feature to make relativistic corrections (about +1e-16
per meter above sea level). For example, my house is at
elevation 1000 ft (~ 300 m) so I would set my Cs freq offset
about -3e-14 to compensate. But verify the long-term stability
of the standard before you worry about subtle details like that.

> I don't have a feel for how well the automatic adjustments actually work, maybe 
>  Tom can comment?

I haven't done that with my 4065B yet so could you take a few
days to try it on yours? Just power it up cold and measure it
against GPS for a few days to get the mean frequency error.

Then repeat this half a dozen times and see what the "retrace"
error is. Depending on the actual stability of your 4065B, and
the resolution of your GPS and TIC, you might have to extend
each run for a lot more than a couple of days.

As for your subject question, sorry, I don't have a handy list of
model number differences.

/tvb