On 11/03/13 21:20, John Miles wrote:
With most modern lightweight Rb's the OCXO is integrated into the same
heater block as the physics package. That makes it a bit tough to heat one
without heating the other. .
On LPROs the OCXO sits on the opposite side of the board.
Pretty sure that's not an OCXO. If it is, it's a tiny one that will warm up
very quickly. I doubt it's even a TCXO, though.
Considering that the sweeping ranges +/- 15 ppm, it needs to be pretty
good at least. TCXO is doable and the OCXO does not need to be very
advanced. There is a heat-sink on the crystal assembly. It would make
sense if it is an OCXO as the surrounding would be on the hot side while
operating, so increase heat dissipation in order to keep it in balance
would make sense.
The fact that we don't know the details is a side-effect of not
reverse-engineering them properly.
Of the Rb standards I've seen, only the PRS-10 and HP 5065A use OCXOs. I'd
assume that the old-school Tracor and R&S models also used OCXOs, but for
the cheap telecom modules it would have been seen as a waste of money.
The R&S XSRM has an OCXO, so does my russian one.
Also, the HP 5065A has separate ovens for the lamp and resonance cell, but I
believe the smaller units use a single heater for both. They won't lock
until the heater is up to temperature.
You need to keep two different temperatures of the lamp (~70) and cell
(~110), unless you tweaked it with buffer gas, which might be what they
have done.
Cheers,
Magnus
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