[time-nuts] Re: DOXCO from Z3801

[Bob Camp]

Hi

Other than sitting down and talking to the folks who actually designed it and who
ran the design process, no I don’t have any direct info. I do know that, based on 40+
years as an OCXO designer that the approach used is nonsense. You could do a much 
better job *if* stability was the target. Since it was not why they did it this way, that’s in 
no way a knock on those folks. They did what they needed to do.

Bob

> On Dec 9, 2022, at 4:24 PM, ed breya via time-nuts <time-nuts at lists.febo.com> wrote:
> 
> I would like to figure out for sure whether the outer oven in the Z3801A OCXO is a benefit or not. Does anyone know of actual experiments, studies, correspondence, hypotheses, or other documents, or personal experience/knowledge specifically pertaining to this unit, indicating problems with the thermal stability or uselessness of the outer oven? I have seen all sorts of commentary on this over the years, but is it conjecture, or fact?
> 
> I have done some searching around over the years, and recently, and found nothing specific about it. I may not know best where or how to look, but I think I'm doing it OK - it appears sparse so far. I'd appreciate if anyone can post up any links to such info.
> 
> I have studied some more general papers found, like Rick's ones about designing better OCXOs. I know that the Z3801A's OCXO is far from perfect, and the inner and outer ovens etc are not optimally arranged, so there may be possible weaknesses, but I'm looking for actual known or discovered problems in actual use.
> 
> If there is a fatal flaw in the design or application of the outer oven, then I doubt it's worth trying to improve it much - so many cycles of taking apart and reassembly would be risky to the guts.
> 
> If it actually can't be blamed for anything, then I think it should be beneficial to the thermal stability of the OCXO inside. I think it should help especially in holdover mode, against temperature fluctuations.
> 
> I would think that someone with a Z3801A and the right analysis gear could do some experiments to look for thermal instabilities (oscillations etc due to interaction of the control loops) under at least some typical conditions (but not exhaustive, unfortunately).
> 
> Also, it should be possible to see if it helps or not in normal and holdover modes, with the outer oven working or disabled, while subject to certain temperature variations. I have a Z3801A, but none of the other stuff needed to see what's actually going on.
> 
> If someone has done some of the above tests (or similar) in the past, a report on it is a perfect example of the kind of documents I'd like to see.
> 
> Ed
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