[time-nuts] How to create a super Rb standard

[Bob Camp]

Hi

You would need to redesign the Rb to work in a vacuum. There is a lot involved
in doing that. They depend on the air inside the package to properly operate the
heating in the physics package. Different parts of the package are at different 
temperatures. Without the air cooling the temperature offsets could not be properly 
maintained. 

There are a *lot* of differences between the GPS Rb’s and the ones we buy on
eBay. The fact that they operate in pretty far down the list of significant differences.
The most simple answer to “why” the Rb is better is that the design requirements
on the two standards were different, as were the design teams. Coming up with 
an Rb with better short term stability is the way that all worked out. That short 
term stability is better than other large cell Rb designs, but not by a crazy amount. 
How much better it is depends a lot on which large cell Rb design you compare to.
It also depends a bit on which specific unit you are looking at.

All that said, space benign is indeed a pretty quiet environment. It certainly does 
help a bit if you operate there. There is also data on the GPS Rb’s that show them
doing quite well on the ground. So no, it’s not all space, but space does not hurt
their performance. 

Bob

> On Jan 18, 2017, at 12:23 AM, Li Ang <379998 at qq.com> wrote:
> 
> Hi
> I am wondering if anyone tried to put a Rb unit into a vacuum container. And how much the performance is improved? Someone told me that's why the Rb clocks are more stable than Cs clocks on the GPS satellites.
> 
> LiAng
> 
> ---Original---
> From: "Bob Camp"<kb8tq at n1k.org>
> Date: 2017/1/17 21:20:23
> To: "Discussion of precise time and frequency measurement"<time-nuts at febo.com>;"Perry Sandeen"<sandeenpa at yahoo.com>;
> Subject: Re: [time-nuts] How to create a super Rb standard
> 
> 
> Hi
> 
> Since the physics package in the small Rb’s is different than the stuff in the large units, 
> you have some basic limits on what you can do to improve them. The main things people
> have done are to modify them to turn off the temperature compensation and replace it
> with some sort of precision controlled thermal enclosure. Pressure compensation is a good
> idea on any of these parts (large or small). How much your particular unit benefits is a 
> “that depends” sort of thing.
> 
> Bob
> 
>> On Jan 16, 2017, at 10:24 PM, Perry Sandeen via time-nuts <time-nuts at febo.com> wrote:
>> 
>> 
>> List
>> It looks like their is as infinitely small chance of being able to get 5065.
>> So what can be done with the telco Rb's (mine are analog tuned) to wring the best possible performance from them? Sooper Duper power supplies, Peltier (sp) cooling modules?
>> Regards,
>> Perrier
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