[time-nuts] 10811-60105 and -60111

[Poul-Henning Kamp]

In message <4122376B.2080706 at usa.net>, Alberto di Bene writes:
>Tom,
>
>  thanks for the answer. I was asking as often I see the -60105 submodel
>offered on eBay at attractive prices. Now I know why, but maybe you are 
>right,
>aged OCXOs can give surprises.
>
>Talking of OCXOs, supposing I want to build an outer oven around a 10811,
>which could be the right temperature ? Anybody knows the outer oven 
>temperature
>of the double ovenized 10811 used in the Z3801A ?   Thanks.

I experimented a bit with this.

The temperature you choose is not important as long as it is not
close to or higher than the internal oven temperature.  Simple
physics dictate that if you OCXO is rated 0..70C you can trust the
internal oven to be above 70C.

I found that passive insulation of 5..10cm high quality foam performed
as well as any kind of heating I could come up with.

Hunt around metrology information and find out how they construct
the ovens they use when they calibrate equipment and you will find
some serious temperature regulation:  I saw one which consisted of
an internal block of aluminium approx 30x30x10cm (with a small
hole in the center for the device under test) packed in 10cm of foam
inside a box of 2.5cm thick aluminuum which was peltier regulated
on all six sides and then encapsulated inside another layer of
10cm foam.  They still thought they could do it better...

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