[time-nuts] need recomendation for a portable 10mhz reference oscilator

[Bruce Griffiths]

Hal Murray wrote:
>> A good (and well-aged) double-oven OCXO with aging compensation should
>> be able to provide that type of performance. The problem is: how
>> much physical movement will the unit experience? What are the
>> temperature extremes that are expected, and how fast does the
>> ambient move between the temp extremes? Can it be GPS locked during
>> that time? 
>>     
>
> Assuming you don't GPS lock it...
>
> How well will two units from the same manufacturer/batch track?
>
> I'm assuming they will see roughly the same temperature profile and that you 
> start with them running at the same frequency.
>
>
> Has anybody made a triple oven setup?  I'm thinking of a big box with a few 
> holes and a temperature controlled fan.  The idea is to let the oven (and 
> electronics) keep itself warm when the ambient temperature gets very cold.
>
> I'm picturing an open hill top at night with clear skies so there would be 
> lots of radiation cooling.  Of course, with an open hill top, GPS recption 
> would be easy.
>
>
>
>   
Hal,

A triple oven is a particularly bad idea, its just too difficult to
achieve a wide operating temperature range without losing temperature
control or cooking everything in the innermost oven unless one uses a
watercooled peltier device to control the outer oven temperature.

A well designed single oven with feedforward (or the outer oven of a
dual oven system if you cant redesign/rebuild the inner oven) can easily
achieve a thermal gain of more than 1E5 see:

http://tf.nist.gov/timefreq/general/pdf/595.pdf



A bootstrapped oven design like that used by Wenzel (not as new as he'd
have you believe - its been in use in one form or another for the better
part of a century) will also help in improving performance. The optimum
solution is of course to combine the 2 techniques.

http://www.wenzel.com/documents/Sub-pico%20Multiplier.pdf

With a thermal gain of 1E5 for the outer oven temperature fluctuations
at the outer shell of the inner oven will only be a 1 millikelvin or so
(assuming the ambient temperature range is less than 100K).

Bruce