[time-nuts] hp 10544A and 10811A ovenized oscillators

Bob kb8tq kb8tq at n1k.org
Mon Nov 5 13:10:00 EST 2018


Hi

A failed ( = cold) oven on either a normal OCXO should give you a “tens of ppm” sort of frequency 
error. At 10 MHz that would be over 100 Hz.  Fractions of a ppm are less likely to be oven issues. 

Bob

> On Nov 5, 2018, at 1:01 PM, Dr. Frank <frank.stellmach at freenet.de> wrote:
> 
> Walter,
> 
> did you check on both failing oscillators, that the ovens work properly afterwards, or that the cases still get warm?
> 
> I once had a failing 10811, where the NTC was defect, maybe also after a longer unused time.
> 
> As the heater draw an excessive current on turning on, (about 500mA for the 10811), maybe the thermal fuse blew up, but due to the peaking current, not due to temperature.
> 
> I find it quite unusal, that the oscillator / XTAL itself should make a jump like this.
> After 48h at most, it should return to its recent frequency trimming, within < 1E-8, or less.. as these guys are really old.
> 
> That's the typical behavior of all three 10811, which I own (inside 5370B, 5335A, and one external).
> 
> Frank
> 
> 
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