[time-nuts] hm H Maser

Bob kb8tq kb8tq at n1k.org
Tue Jan 10 18:02:35 EST 2017


Hi

> On Jan 10, 2017, at 5:26 PM, Bob Stewart <bob at evoria.net> wrote:
> 
> This may be a dumb question, but how much of an H Maser's advantage over a Cs Standard, for us mere mortal time-nuts, is down to the output oscillator it uses, rather than the reference source (H MASER or Cs beam)?

Pretty much none. You *can* design one with a crummy OCXO, but the question becomes - why would you do that? Putting a $10,000 OCXO into a $150K device is not that big a deal. If you put the same OCXO into a Cs standard, it would run a bit better out to the cross over point (a few 100 seconds or so). Indeed *some* Cs standards have such OCXO’s in them and that’s what they do. 

Bob

> Bob
> 
>      From: Dr. David Kirkby (Kirkby Microwave Ltd) <drkirkby at kirkbymicrowave.co.uk>
> To: Discussion of precise time and frequency measurement <time-nuts at febo.com> 
> Sent: Tuesday, January 10, 2017 4:12 PM
> Subject: Re: [time-nuts] hm H Maser
> 
> On 10 January 2017 at 15:35, Ole Petter Rønningen <opronningen at gmail.com>
> wrote:
> 
>> ... having said that, I for one think I'm with Bob on this one. The thing
>> about masers are that they are big. At least active masers. And they
>> require a substantial volume be kept at ultra high vacuum - which is not
>> trivial, especially not in a homeshop. The cavity needs to be kept at a
>> temperature stable to 0.001 degree C. With 4-5 magnetic shields. Add to
>> this costly pumps to keep the vacuum this low even if you succeed at
>> reaching that vacuum.. There's easily 1-2KUSD running cost per year just to
>> keep the maser running.
>> 
> 
> Looking at the Microsemi MHM 2010 Active Hydogen Maser data sheet, the
> maser has a peak power of 150 W and an operating power of 75 W.  Based on a
> power consumption of 75 W, that is 657 kW hr / year of energy. I pay around
> £0.20 (GBP) per kW hr for electricity, so that's £131 (GBP) annually. I
> believe electricity is cheaper in the USA than here in the UK, but
> converting £131 (GBP) to USD, that's around $161/year in electricity. So
> running costs don't seem to be an issue.
> 
> But I must admit, the thought of spending a lot of time/money to build
> something I could have bought for a lot less with higher performance is not
> that attractive, although of course there would be a satisfaction from
> building it yourself.
> 
> Dave
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> 
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