[time-nuts] 10811 foam enclosure

[WarrenS]

IMHO, The dual oven 10811 oscillators I've seen are not designed as some 
hack JUST to do a quick warm-up.
The six sided heater and all the trouble they went thru to insulate the 
inside oven from any effects from the outside is a design meant to keep the 
inside oven highly isolated from wide ambient  temperature changes.
The fact that the outside oven is such an overkill in both the total power 
it can supply and how isolated it keeps the inside, It will surely do both.
The outside oven on mine runs at 1/100 of it's max heating power, and any 
osc frequency change caused by normal room temperature changes is will below 
the oscillator's noise level.
In other words, normal lab temperature variations, have NO measurable effect 
on the Dual Oven 10811's frequency, something that can NOT be said of the 
single oven unit's I've tested.
ws

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At 07:59 AM 1/10/2011, Bob Camp wrote...
>>The spec they were after was a warmup to "on frequency +/- 1x10^-8"
>>from -40 C sort of thing. I believe the warmup  time was under 15
>>minutes, but I don't know the exact number.

>Nope. It was only spec'd for operation from 0-50C. It was required to
>achieve satellite lock within 60 minutes of powerup, but only had to
>achieve +/- 1 us (PPS) while locked. Freq spec was < 10E-9 one day
>average. You don't even need an OCXO to do all of that.
>
>As I already stated, the warmup/training spec allowed 24 hours, after
>which it was expected to be able to holdover for 24 hours within 7 us.
>This, while experiencing temperature cycles (0-30C, 20-50C). The
>successor, the GPSTM, doubled the warmup to 48 hours, but added an
>additional temperature range (35-65C) to the holdover requirement.
>
>The double oven was there for holdover stability, not warmup time.