[time-nuts] HP10811 dual oven

Charles Steinmetz csteinmetz at yandex.com
Wed Aug 5 11:13:55 EDT 2015

Pete wrote:

>When I got it, my luck won this time, one of the coax
>cables is tagged 10 MHz and the other EFC.

That, by itself, does not differentiate between an HP 10811 and the 
Symmetricom OCXO -- they are identical 10MHz oscillators externally 
(the doubler in the Symmetricom is internal).  In my experience, the 
only conclusive external feature is the presence or absence of the 
Hewlett Packard ID on the serial number sticker.  10811s have a 
serial number sticker with Hewlett Packard ID (see photo below).  If 
the serial number sticker doesn't have the HP ID, it is the 
Symmetricom oscillator.

As I noted, having the Symmetricom oscillator is not necessarily a 
bad thing -- mine is better than all of my 10811s, including the 
selected 10811 that came out of an HP5390A frequency stability 
analyzer.  (This should NOT be read as a claim that the Symmetricom 
oscillators are better than 10811s -- my sample of the Symmetricoms 
is way too small to justify any conclusion in this regard.  But this 
particular Symmetricom happens to be a very fine "10811 class" OCXO.)

Best regards,

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