[time-nuts] HP10811 vs 00105 OCXO

[Bob Camp]

Hi

The outer oven in the 3801 was put there for a very specific purpose:

When the 3801 was designed, they had a target specification that included a warmup from -40C.
The 10811 was never designed to work at these temperatures and simply could not meet the 
required warmup time. 

The “solution” that they came up with was to put a heater around the 10811 (without modifying it 
internally) to get the case up to a fairly high temperature quickly. This allowed them to meet the 
-40C specification on their target sheet. As it turns out, it is very unclear if the 3801 ever went into
the sort of environment that would expose it to that sort of low end temperature.

HP published a number of papers on the 10811 and it’s successor. They go into great detail about 
the thermal optimization of the part and why you can easily have “to much of a good thing” and actually
make the oscillator worse.

Bob


> On Aug 7, 2015, at 3:14 AM, timeok at timeok.it wrote:
> 
> 
> Hi  Corby,
> 
> I agree with you that if selected, there may be many differences between objects of the same type. Unfortunately it is very difficult to know what is selected and what is not. For example I found a 10811 mounted in a  Z3801A  who have the temperature set-point  completely wrong. I remember that TVB has done tests on a number of Z3801s and the results were very different from one  to each other. In fact I would expect HP since it is bothered to put a second oven in Z3801A, had selected the oscillators but it is not.
> 
> I have not yet measured the 105 Phase noise, I have a 5MHz reference is -115 and -135 dBc respectively at 1 and 10 Hz.
> 
> Luciano
> www.timeok.it
> 
> 
> 
> 
> On Thu 06/08/15 20:38 , <cdelect at juno.com> wrote:
> 
>> Luciano,
>> 
>> I have found that "selected" 10811 units will offer significantly better
>> short term stability as a stand alone or open loop oscillator over the
>> 105 style oscillator. (Mid parts in 10-13th from 1 to 100 Seconds)
>> 
>> However with the 5065A locked the performance will be driven by the loop
>> and both styles will give similar performance.
>> 
>> Cheers,
>> 
>> Corby
>> 
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