[time-nuts] Why using HP5370 ext-ref is (maybe) a bad idea...

Burt I. Weiner biwa at att.net
Sat Mar 1 14:22:09 EST 2014

I don't know if this has any value here, but several years back I had 
a problem with my IFR-1500 Service Monitor.  When I would externally 
lock it to my 10 MHz DATUM I would see jitter in the signals being 
measured with the IFR.  It turned out to be leakage in the IFR's 
solid state switch that was allowing some of the internal oscillator 
to be mixed in with the external reference.  I added a 2N2222A 
transistor to short out the internal oscillator's output to the 
original switch.  The 2N2222A's base is fed from the "Ext REF" LED 
voltage. This solved the problem.

Burt, K6OQK

>From: Magnus Danielson <magnus at rubidium.dyndns.org>
>Subject: Re: [time-nuts] Why using HP5370 ext-ref is (maybe) a bad idea
>On 01/03/14 18:20, Brian Lloyd wrote:
> > Instead of using the external reference input, any thoughts on actually
> > disciplining the internal OCXO to bypass the problem?
> >
>Considering that it's a HP10811A, it shouln't be too hard.
>In general, doing a new A8 board might be an option.

Burt I. Weiner Associates
Broadcast Technical Services
Glendale, California  U.S.A.
biwa at att.net

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