[time-nuts] Re: Austron 1250A ADEV Hump

[Magnus Danielson]

Hi Jim,

There is really two paths into your measurements which can cause this:

1) Some form of environment (which include oven oscillation itself) 
modulation the oscillator frequency
2) Some form of environment modulating the counter measurement

One approach is to measure voltage, current, temperature etc. to see if 
any of that correlates.

I've myself found a highly unstable oven, and the tell-tale was an ADEV 
bump at 3 s, which is not where we expect one. I then was able to see it 
on the PSU current, and power-cycling the output triggered a HUGE ring 
that rang out to a remaining oscillation. The oscillator vendor 
investigated the sample I gave back to them, and they learned the hard 
way they made a mistake. They reported it just fine, but their salesman 
missed by saying "it meets specs" which I replied "I still can't use 
it". So, it can very well be that. Sometimes the exact condition for the 
OCXO can make it get similar missbehaviours.

There is also things in reference and counter that can mess with you in 
similar way. Trying different setups to rule out where it happens can help.

Sometimes a bad trigger-point can be the culprit. Guess how I know...

Happy hunting! You learn a lot from doing that.

Cheers,
Magnus

On 2024-08-08 04:55, AC0XU (Jim) via time-nuts wrote:
> Time Nuts:
>
> I have a few Austron 1250As. One of them has an ADEV with a large hump at around 50 secs time scale (2E-11). Using a 53230A counter, I can convince myself that I can see the frequency go up and down at around that period.
>
> I guess that this is an oscillation in the oven circuits.Anyone have an idea whether this is curable and how?
>
> Thanks!
> Jim
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