[time-nuts] Interesting HP oscillators...

[Richard (Rick) Karlquist]

On 1/13/2014 7:36 PM, Rex wrote:
> This document lists that part number...
>
> http://www.leapsecond.com/museum/10811a/90027-1.pdf
>
> It says (I think -- in a quick scan) that it is mostly the same specs as
> a 10811 D/E except a narrower EFC tuning range.

When HP was doing the smart clocks circa 1997, they ignored
my advice against trying to steer the EFC in favor
of using a fix tuned oscillator followed with a
synthesizer.  The reason for this was
the lack of suitable DAC's, and even if you found one,
then you have to have a suitable reference source with
low enough noise, and even if you found one, it would
have to be ovenized.  The E1938A had an available ovenized
reference, however, the 10811 (as everyone knows) has
only a Zener diode, and it is not very well ovenized
This version (which I never heard of until now) probably
ditched the Zener diode which (besides eliminating drift
from the Zener) narrowed the EFC range.
Narrowing the EFC range on the 10811 was a band aid
that contributed another bit or three to the error budget.
You had to make some assumption about long term aging
and how often it was OK to ask the customer to readjust
the mechanical trimmer.  Also, there was the fact that
no base station was going to be in service for more
than a few years, as it would be obsolete by that time.

Rick N6RK