[time-nuts] Re: ammonia, cesium, masers, etc.

[paul swed]

According to one of the articles 23,870,129.007 Hz +/- 10 Hz. That may have
been the measurement limit at the time and the technology.
Paul

On Mon, Sep 20, 2021 at 1:15 PM Andy Talbot <andy.g4jnt at gmail.com> wrote:

> What's the exact resonance frequency of ammonia?   To as many sig figures
> as it's been calculated.
> Googling just seems to throw up "approximately 23.8GHz"
>
> Andy
> www.g4jnt.com
>
>
>
> On Mon, 20 Sept 2021 at 18:10, paul swed <paulswedb at gmail.com> wrote:
>
> > Well at the very next MIT flea I will grab some 23 GHz waveguide. Maybe
> > Nearfest in October. Another trick I have actually used on 10 GHz id 3/4"
> > copper tube as waveguide. Its quite low loss but circularly polarized. So
> > to use it I needed to rotate the coupling in the shack for best return
> > loss. So perhaps 1/2" or 1/4" would be the same. At least in the earliest
> > Amonia system they simply seemed to have filled the waveguide with
> amonia.
> > Then launched 23 GHz down the length of it. Good thing about amonia if
> you
> > have a wave guide leak you would know it.
> > Indeed there is a ton of modern 23 GHz technology available. I was going
> to
> > make some comments on system oscillators and deleted them. I haven't
> looked
> > at what types of oscillators or multipliers are out there at a cheap
> cost.
> > All this being said its a curious possibility. But if its no better then
> a
> > Cesium not worth any effort. Its one serious advantage is you could
> refill
> > the amonia. Not really sure what would get used up. I think as mentioned
> > here the amonia H would disassociate.
> > Regards
> > Paul
> >
> > On Mon, Sep 20, 2021 at 11:07 AM Lux, Jim <jim at luxfamily.com> wrote:
> >
> > > On 9/20/21 7:17 AM, Poul-Henning Kamp wrote:
> > > > --------
> > > > paul swed writes:
> > > >
> > > >> Though honestly bending 23 GHz waveguide might be tricky. Or simply
> > > leave it
> > > >> straight after all it Amatuer grade.
> > > > I seem to recall that there was about 10-ish meter coiled up in the
> > > > one on the famous old picture.  That might be a bit unwieldy.  On the
> > > > other hand, that was probably not waveguide as much as just plain
> > > > copper-tubing ?
> > >
> > > That would depend on whether you want to control moding. (the picture
> > > says rectangular) Bending WG is pretty easy if the radius is large
> > > compared to the size of the WG - it's very soft copper, so you just
> need
> > > an appropriate form around which to bend it. The trick of filling it
> > > with sand also helps.  At 23 GHz, you probably want to use WR34 or WR42
> > > (Hmm, probably the bigger, so you're farther from cutoff, 17 and 14 GHz
> > > respectively).
> > >
> > > >
> > > >> Lastly they discussed an Amonia maser. Never knew. Wonder if it
> > actually
> > > >> vented amonia slowly. Sort of sounds that way.
> > > > I would suspect the main problem with an amonia maser is that the
> > > > Amonia disassociates and the hydrogen leaks out though the metal ?
> > > >
> > > I wonder, though, if you were "building your own atomic clock" whether
> > > ammonia might not be easier than Cs or Rb, for instance. These days a
> 23
> > > GHz oscillator and other parts are fairly easy to come by, and ammonia
> > > is somewhat easier to handle than Cs or Rb. I would normally think you
> > > can get any of them by just ordering them, but since ammonia is used in
> > > synthesis of methamphetamine, it may not be so easy to get a small
> > > bottle of ammonia gas.
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