[time-nuts] Frequency processing scheme of HP5065 vapour rubidium standard

[Ulrich Bangert]

Hi folks,

please be assured that I do not want to argue away the existence of
these dependencies! 

> > They don't have a "correct" frequency, only a very stable frequency.
> > 
> > The actual resonance frequency of a rubidium standard depends
amongst 
> > other things on the partial pressures inside the physics package.
> 
> Other issues includes the exact frequency pulling of the 
> cavity wall, cavity tuning and the mixture of buffert gas 
> which to some degree compensates the wall pulling.

Agreed! But you are talking about things that happen INSIDE the physics
package, don't you? Ok, let us assume that there WERE big differences in
the physics packages that need to be compensated for. In THIS case the
tunable synthesizer would indeed make sense and even more the printed
synthesizer settings on the physics packages! If this were the only
information available, i would immediatly agree to you!

However, when i look into the circuit drawings of my FRK-L it is beyond
any question that it uses a FIXED FREQUENCY SYNTHESIZER unlike the
HP5060 which uses the described tuneable synthesizer. And that arises
the question how Ball/Efratom/Datum/Irvine manage to do it with a fixed
frequency synthesizer (even exchange of the physics package) when HP
needs a tunable synthesizer. 

IMHO this can only be possible with one of the two following conditions
given:

1) The Ball/Efratom/Datum/Irvine physics packages do have tighter
frequency specifications than the HP ones (some orders of magnitude)

2) There is analogue way to pull the atomic resonance to a kind of
'setpoint'.

I screwed quite a bit to get my FRK running ok. The lamp temperature was
not ok and the plasma excitation frequency was also. I know there are
lots of parameters having a subtle but measurable influence on the
atomic resonance. Efratom even specified the coefficient for atmospheric
pressure, but all of this are very SUBTLE and easily compensated for
with the C-field which gives a total +/-10E-9 freqency control range.
+/-10E-9 makes about +/-0.7 Hz absolute at the rubidium's resonance
frequency.

The HP tuneable synthesizer is tuned in app. 1 Hz steps (!) and allows
for offsets up to a stunning 1 KHz! 

Cheers
Ulrich  


> -----Ursprüngliche Nachricht-----
> Von: time-nuts-bounces at febo.com 
> [mailto:time-nuts-bounces at febo.com] Im Auftrag von Magnus Danielson
> Gesendet: Montag, 6. November 2006 16:01
> An: time-nuts at febo.com; phk at phk.freebsd.dk
> Betreff: Re: [time-nuts] Frequency processing scheme of 
> HP5065 vapour rubidium standard
> 
> 
> From: "Poul-Henning Kamp" <phk at phk.freebsd.dk>
> Subject: Re: [time-nuts] Frequency processing scheme of 
> HP5065 vapour rubidium standard
> Date: Mon, 06 Nov 2006 13:21:50 +0000
> Message-ID: <4604.1162819310 at critter.freebsd.dk>
> 
> > In message <000001c701a5$5f076420$0202fea9 at athlon>, "Ulrich 
> Bangert" 
> > writes:
> > 
> > 
> > >But what surprises us completely is the fact that 
> different physics 
> > >packages need DIFFERENT thumbwheel settings to generate 
> the SAME time 
> > >scale as seen with the two devices available.
> > 
> > This is because rubidium vapour standards are not primary standards.
> > 
> > They don't have a "correct" frequency, only a very stable frequency.
> > 
> > The actual resonance frequency of a rubidium standard 
> depends amongst 
> > other things on the partial pressures inside the physics package.
> 
> Other issues includes the exact frequency pulling of the 
> cavity wall, cavity tuning and the mixture of buffert gas 
> which to some degree compensates the wall pulling.
> 
> Cheers,
> Magnus
> 
> _______________________________________________
> time-nuts mailing list
> time-nuts at febo.com 
> https://www.febo.com/cgi-> bin/mailman/listinfo/time-nuts
>