[time-nuts] Better than average Rb oscillator

[Attila Kinali]

Hoi Skip,

On Wed, 10 Feb 2021 16:54:41 -0700
Skip Withrow <skip.withrow at gmail.com> wrote:

> This oscillator is a stock standard LPRO-101 with only one slight
> modification.  The 5k C-field pot was brought out external to the unit
> and replaced with a precision 500 Ohm 10-turn pot with fixed resistors
> on either side to make the total 5k.  The frequency change is about
> 1.62x10E-13 per division on the turns counting dial.

That's quite a bit better than what I am seeing. 
Attached are my plots of a LPRO-101 in an Lucent KS-24361 RFTG
measured against a Trimble UCCM GPSDO (antenna on building
roof, about 20m above ground, ~5m below highest obstacle)
using a Philips PM6880 every second.

The Rb had been running for about 30ish days before I started
the measurement on 2020-07-03 and ended on 2020-09-18.
Environment is a normal office room where nobody walks in, usually. 
Temperature is not stabilized.  During the measurment changes of
up to ~1°C per day were seen The "kinks" in the phase plot are not 
correlated with temperature, though, neither do they seem to be
correlated with barometric pressure. But I haven't done a
statistical anaylsis on environment parameters, yet. 

The Rb is still running and measureing, but the ADEV doesn't look
any different. Flicker floor seems to be about factor 2 lower, but
that could be a side effect of the heating now being on and thus
stabilizing the temperature somewhat.

So, this raises the question: why is your LPRO so much better?
I mean, going straight down to 1e-14 is on par with the best
research Rb standards I am aware of. 

			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
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