[time-nuts] Nifty old GR OCXO?

[Dr Bruce Griffiths]

Tom Van Baak (mobile) wrote:
>> eBay item 150082419799 (Genrad 475-C)--is this some kind of OCXO frequency
>> reference?  From the description, it sounds like it might be used to
>> monitor a broadcast transmitter frequency.  Be sure and scroll down and
>> check out the wood and foam oven box and the "quartz plate" resonator.
>>
>> The '56 GR catalog at the bama site doesn't show a 475-C, but that's not
>> surprising as the 475-C looks quite a bit older.
>>     
>
> Yes, that's a nice example of a mercury thermometer
> regulated, ovenized quartz plate oscillator, complete
> with balsa wood case and lots of asbestos (not foam)
> insulation. I have a couple of these ovens -- though
> with 100 kc xtals, not the special broadcast freq.
> spkr_volume -- please send me email, OK?
>
> For other old GR oscillator stuff see:
> http://www.leapsecond.com/museum/gr1103a/
> http://www.leapsecond.com/museum/gr1190a/
> http://www.leapsecond.com/museum/gr676b-50kc/
> http://www.leapsecond.com/pages/old-genrad/
>
> Of special note, see the 4 patents I have there
> on the web page, like this one:
> http://www.leapsecond.com/museum/gr676b-50kc/US1967185.pdf
>
> Would you believe that GR had double ovens all
> figured out back in 1931? HP wasn't the first...
>
> /tvb
>
>
>
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>   
Tom

The mercury regulator evolved into the mercury toluene regulator used at 
NBS (and elsewhere) in the 60's and earlier to control the temperature 
of their standard cell oil baths.
NBs technical note 141 gives some details. Refinements such as 
anticipator windings were employed to achieve temperature stabilities of 
around 1mK or so.

Bruce