[time-nuts] Double ovened 10811-60158 on ebay

[Richard (Rick) Karlquist]

Didier Juges wrote:

> The designers of the HP E1938 (which never went to full production) went
> through pains to try and keep the gradient evenly distributed precisely for
> that reason. My guess is that it you take the cover out from the E1938, you
> will find a perfectly symmetrical layout around the center, where the
> thermistor is located.

Actually, something like 30,000 E1938A's were built.  Maybe the glass is
not full, but it is not exactly empty.  As I explained in my 1997 FCS
paper, the oven is very symmetrical, etc.  We routinely achieved a
thermal gain of several 100,000.  During design testing, we could often
get the thermal gain up to well over 1 million.    This is the thermal
gain to the crystal.  Of course, the gain to the electronics was less.
The thermal gain of a good 10811 is around 1,000, by comparison.

Rick Karlquist N6RK
E1938A designer