[time-nuts] Better than average Rb oscillator

[Attila Kinali]

Moin Angus,

On Sat, 13 Feb 2021 22:04:54 +0000
Angus via time-nuts <time-nuts at lists.febo.com> wrote:

>    It's not too different from what I got with a temperature
> controlled and air pressure compensated LPRO

May I ask how you do the pressure compensation?

And could you show a phase plot of the measurement?
Our *DEV measurments hide a lot of detail and interesting
features in oscillator behaviour. 

> - apart from the ageing of course! 

Well, IMHO the aging that Skip sees is the big deal.
His ADEV goes straight down to 1e-14. That's on par
with the best research Rb vapor cell standards I am
aware of. And there are no aprubt frequency changes
whatsoever, in his one month measurement. In contrast
to that, I see a jump in frequency ever few days/weeks.

It would be interesting to see where the flicker floor
of Skip's setup is and whether he sees any lamp light
shift induced jumps (these occur somewhere in the order
of a few times a year on the most stable Rb standards).


>    The Hadamard plot shows the performance that can be obtained by
> just adding a GPS to correct for long term ageing.
>    These plots are based on 1000s averages, so look a little better
> than if the 1s data was used.

Well, beyond a day, GPS is more stable than any Rb standard.
If you have GPS always on, then you need the Rb only for
short term time keeping and to bridge any GPS outages.
But, in the sub-1d range, a good OCXO performs as well as
a Rb standard. So you can get away with a lot lower cost and
power, if you have GPS available. So, for me, Rb standards
only become intresting beyond 1d.

			Attila Kinali

-- 
The driving force behind research is the question: "Why?"
There are things we don't understand and things we always 
wonder about. And that's why we do research.
		-- Kobayashi Makoto