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

[paul swed]

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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