[time-nuts] hm H Maser

Bob Camp kb8tq at n1k.org
Sun Jan 8 11:26:58 EST 2017


Hi

> On Jan 8, 2017, at 11:21 AM, Dr. David Kirkby (Kirkby Microwave Ltd) <drkirkby at kirkbymicrowave.co.uk> wrote:
> 
> On 8 January 2017 at 15:22, Bob Camp <kb8tq at n1k.org> wrote:
> 
>> Hi
>> 
>> I guess the question then would be:
>> 
>> Is a H Maser that runs 6.6 x 10^-12 at 1 second worth the trouble?
>> 
>> With 100 KHz / C temperature coefficients running around, getting
>> good stability in a real world setting at 1 day will be “interesting”.
>> 
>> Just for reference:  The MH-2010 data sheet shows 1.5x10^-13 at
>> 1 second for the “cheap” version and 8x10^-14 at one second for
>> the low noise version.  Data showing the 5065 Rb at 1x10^-12 at
>> 1 second is running around on various web sites.
>> 
>> The NIST paper suggests that they made several prototypes before
>> they got one good one working. That’s a lot of “fun and games” with
>> ceramic machine lathes and Rb magnetometers…..
>> 
>> The punch line being - would the same effort / cost / many years of time
>> be more
>> fruitful (ADEV wise) doing a large package Rb (like a 5065) ?  Based on
>> the number of people making them in volume over the years, Rb’s appear to
>> be the easier item to debug, design, and build.
>> 
>> Bob
>> 
> 
> If you build a H2 maser, you would learn a lot more than building a bunch
> of rubidiums. That sounds a good enough reason to me.


I’m not sure I agree with that. Both have their own issues. Much of the learning
in both cases involves fiddly mechanical and machining details. Working each
out by a lot of trial and error would be useful for that particular standard. It’s hard
to see how it would be useful for much else …. Yes, there is a bunch of obscure
physics involved in each, but again it’s very use specific stuff. 

Bob

> 
> I've been contemplating buying one of the older HP 5061A or 5061B cesium
> frequency standards from eBay. Almost all are sold as "for spares or
> repair", and are probably not going to be economically viable to get
> working due to the fact the tubes are probably useless. But I'd sure learn
> a lot from playing around inside one of the older ones.
> 
> Dave
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