Date   

Re: Observing the ammonia resonance

Neil Smith G4DBN
 

I have an Rb reference here that works that way, using a change in the light transmission of the vapour at resonance for detection by wobbling the source and looking for the second harmonic of the modulation which will peak when the central frequency is bang on the absorption line.  I guess we could use one of the 23 GHz Wavetek boards as a detector, but would there be a difference in the ground states without the presence of an electric field?  Bit too late at night for quantum.

I still want a maser.  I am SO cheesed off that I sold my vacuum pump because I couldn't imagine a use for it. Ha!

Neil G4DBN

On 20/09/2021 23:50, Robin Szemeti - G1YFG wrote:
Have a look at page 32 of the HP 5065A rubidium manual, it describes the lock process quite nicely, a similar method could be used for amonia if one was so inclined.


We used to maintain a few of these at the BBC for various reasons, mostly to do with remote stations and staying "in sync" with london.

On Mon, 20 Sept 2021 at 23:21, Neil Smith G4DBN <neil@...> wrote:
OK, found it.  Should have known.... Feynmann Lectures on Physics,
Section III, number 9, "The Ammonia Maser".

https://www.feynmanlectures.caltech.edu/III_09.html

It looks a whole lot less scary than I recall, but I got the explanation
wrong, it is actually a full flip of the molecule in an electric field
gradient, not the Nitrogen atom. the centres of mass stays where it is,
but the molecule itself flips over.  If it is in the higher energy state
in the electric field, it can be stimulated to emit a photon, and that
is how a maser (or laser) works. There's a lot of fierce quantum
notation and Kronecker deltas and stuff, but it's a lovely bit of
exposition.  I wish I'd remembered this when I did an OU degree for a
laugh, as one of the final courses was on quantum mechanics and it would
have been fun to revisit that paper rather than some of the dry stuff we
had to work on.

I see that Charles Townes, the author of the original Masers paper,
preferred to define the M as "Molecular" rather than "Microwave", and
the main use was for ultra low noise microwave amplifiers  rather than
as clocks.

https://en.wikipedia.org/wiki/Maser#/media/File:Charles_Townes_and_first_maser.jpg

Sounds like a lot of fun to be had anyway.

Apologies for incorrect twaddle about the emission mechanism in the
original post, I should research more before posting half-baked stuff.

I want a MASER now.

Neil G4DBN


On 20/09/2021 23:02, Neil Smith G4DBN wrote:
> Trying hard to recall some stuff from decades ago, but I think that
> when you excite the ammonia molecules, there will be many different
> states generated and you need to remove as many of those as possible
> using a gradiant field of some sort.  Pressure needs to be low enough
> to avoid collisions that would cause broadening, and you have to deal
> with the ammonia falling to bits, so some sort of purge/recharge
> approach needs to be considered, or a continuous very weak jet.
>
> Ammonia is sort of pyramidal, with a Nitrogen atom sitting on top of
> three Hydrogens.  The Nitrogen can be in two states, so it either
> contributes to the dipole moment or the hydrogens, or opposes them,
> depending which "way up" the Nitrogen atom is.  The trick is to select
> molecules in the ground state and put them through an electric field
> which will push the two states in slightly different directions, so
> you can send the ones you want through a hole or a slit, then pass
> that into a cavity, where the molecules can then drop back to the
> lower-energy state when they are tickled with a sniff of 23.8 GHz,
> which then reinforces the oscillation and stimulates more molecules to
> flip.
>
> I'll see if I can find the reference.  It was a very very long time
> ago. I recall a load of Hamiltonians and boards full of Dirac notation
> in a lecture in 1976 and thinking how cool that all sounded, but 24
> GHz was a bit too esoteric for 18-year-old me adn I never made the
> connection with amateur radio stuff.







--
Robin Szemeti - G1YFG
-- 
Neil
http://g4dbn.uk


Re: 10GHz Capable Sig Gen WB SG 1

Dave Brown
 

Anyone have the 15GHz version of this? Comments please if you do.

73

Dave, ZL3FJ

 

 

From: UKMicrowaves@groups.io [mailto:UKMicrowaves@groups.io] On Behalf Of Dave via groups.io
Sent: Friday, September 10, 2021 18:54
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] 10GHz Capable Sig Gen WB SG 1

 

Hello Jim,

I bought mine from Aliexpress. Make sure you buy the right version. 

73

Dave G4GLT. 



On 9 Sep 2021, at 21:54, jimbod1973 . <jimbod1973@...> wrote:

Hi All,

I was looking at the WB SG 1 sig gen as described in the May Scatterpoint and was wondering if there is a recommended vendor for these? - ebay shows several different sources, I'm not sure if these are available direct form BG7TBL? What I'm after is a signal source to get my 3cm system going.

Thanks
73 Jim G0MPP


Re: Observing the ammonia resonance

Robin Szemeti - G1YFG
 

Have a look at page 32 of the HP 5065A rubidium manual, it describes the lock process quite nicely, a similar method could be used for amonia if one was so inclined.


We used to maintain a few of these at the BBC for various reasons, mostly to do with remote stations and staying "in sync" with london.


On Mon, 20 Sept 2021 at 23:21, Neil Smith G4DBN <neil@...> wrote:
OK, found it.  Should have known.... Feynmann Lectures on Physics,
Section III, number 9, "The Ammonia Maser".

https://www.feynmanlectures.caltech.edu/III_09.html

It looks a whole lot less scary than I recall, but I got the explanation
wrong, it is actually a full flip of the molecule in an electric field
gradient, not the Nitrogen atom. the centres of mass stays where it is,
but the molecule itself flips over.  If it is in the higher energy state
in the electric field, it can be stimulated to emit a photon, and that
is how a maser (or laser) works. There's a lot of fierce quantum
notation and Kronecker deltas and stuff, but it's a lovely bit of
exposition.  I wish I'd remembered this when I did an OU degree for a
laugh, as one of the final courses was on quantum mechanics and it would
have been fun to revisit that paper rather than some of the dry stuff we
had to work on.

I see that Charles Townes, the author of the original Masers paper,
preferred to define the M as "Molecular" rather than "Microwave", and
the main use was for ultra low noise microwave amplifiers  rather than
as clocks.

https://en.wikipedia.org/wiki/Maser#/media/File:Charles_Townes_and_first_maser.jpg

Sounds like a lot of fun to be had anyway.

Apologies for incorrect twaddle about the emission mechanism in the
original post, I should research more before posting half-baked stuff.

I want a MASER now.

Neil G4DBN


On 20/09/2021 23:02, Neil Smith G4DBN wrote:
> Trying hard to recall some stuff from decades ago, but I think that
> when you excite the ammonia molecules, there will be many different
> states generated and you need to remove as many of those as possible
> using a gradiant field of some sort.  Pressure needs to be low enough
> to avoid collisions that would cause broadening, and you have to deal
> with the ammonia falling to bits, so some sort of purge/recharge
> approach needs to be considered, or a continuous very weak jet.
>
> Ammonia is sort of pyramidal, with a Nitrogen atom sitting on top of
> three Hydrogens.  The Nitrogen can be in two states, so it either
> contributes to the dipole moment or the hydrogens, or opposes them,
> depending which "way up" the Nitrogen atom is.  The trick is to select
> molecules in the ground state and put them through an electric field
> which will push the two states in slightly different directions, so
> you can send the ones you want through a hole or a slit, then pass
> that into a cavity, where the molecules can then drop back to the
> lower-energy state when they are tickled with a sniff of 23.8 GHz,
> which then reinforces the oscillation and stimulates more molecules to
> flip.
>
> I'll see if I can find the reference.  It was a very very long time
> ago. I recall a load of Hamiltonians and boards full of Dirac notation
> in a lecture in 1976 and thinking how cool that all sounded, but 24
> GHz was a bit too esoteric for 18-year-old me adn I never made the
> connection with amateur radio stuff.







--
Robin Szemeti - G1YFG


Re: Observing the ammonia resonance

Neil Smith G4DBN
 

OK, found it.  Should have known.... Feynmann Lectures on Physics, Section III, number 9, "The Ammonia Maser".

https://www.feynmanlectures.caltech.edu/III_09.html

It looks a whole lot less scary than I recall, but I got the explanation wrong, it is actually a full flip of the molecule in an electric field gradient, not the Nitrogen atom. the centres of mass stays where it is, but the molecule itself flips over.  If it is in the higher energy state in the electric field, it can be stimulated to emit a photon, and that is how a maser (or laser) works. There's a lot of fierce quantum notation and Kronecker deltas and stuff, but it's a lovely bit of exposition.  I wish I'd remembered this when I did an OU degree for a laugh, as one of the final courses was on quantum mechanics and it would have been fun to revisit that paper rather than some of the dry stuff we had to work on.

I see that Charles Townes, the author of the original Masers paper, preferred to define the M as "Molecular" rather than "Microwave", and the main use was for ultra low noise microwave amplifiers  rather than as clocks.

https://en.wikipedia.org/wiki/Maser#/media/File:Charles_Townes_and_first_maser.jpg

Sounds like a lot of fun to be had anyway.

Apologies for incorrect twaddle about the emission mechanism in the original post, I should research more before posting half-baked stuff.

I want a MASER now.

Neil G4DBN

On 20/09/2021 23:02, Neil Smith G4DBN wrote:
Trying hard to recall some stuff from decades ago, but I think that when you excite the ammonia molecules, there will be many different states generated and you need to remove as many of those as possible using a gradiant field of some sort.  Pressure needs to be low enough to avoid collisions that would cause broadening, and you have to deal with the ammonia falling to bits, so some sort of purge/recharge approach needs to be considered, or a continuous very weak jet.

Ammonia is sort of pyramidal, with a Nitrogen atom sitting on top of three Hydrogens.  The Nitrogen can be in two states, so it either contributes to the dipole moment or the hydrogens, or opposes them, depending which "way up" the Nitrogen atom is.  The trick is to select molecules in the ground state and put them through an electric field which will push the two states in slightly different directions, so you can send the ones you want through a hole or a slit, then pass that into a cavity, where the molecules can then drop back to the lower-energy state when they are tickled with a sniff of 23.8 GHz, which then reinforces the oscillation and stimulates more molecules to flip.

I'll see if I can find the reference.  It was a very very long time ago. I recall a load of Hamiltonians and boards full of Dirac notation in a lecture in 1976 and thinking how cool that all sounded, but 24 GHz was a bit too esoteric for 18-year-old me adn I never made the connection with amateur radio stuff.


Re: Observing the ammonia resonance

Neil Smith G4DBN
 

Trying hard to recall some stuff from decades ago, but I think that when you excite the ammonia molecules, there will be many different states generated and you need to remove as many of those as possible using a gradiant field of some sort.  Pressure needs to be low enough to avoid collisions that would cause broadening, and you have to deal with the ammonia falling to bits, so some sort of purge/recharge approach needs to be considered, or a continuous very weak jet.

Ammonia is sort of pyramidal, with a Nitrogen atom sitting on top of three Hydrogens.  The Nitrogen can be in two states, so it either contributes to the dipole moment or the hydrogens, or opposes them, depending which "way up" the Nitrogen atom is.  The trick is to select molecules in the ground state and put them through an electric field which will push the two states in slightly different directions, so you can send the ones you want through a hole or a slit, then pass that into a cavity, where the molecules can then drop back to the lower-energy state when they are tickled with a sniff of 23.8 GHz, which then reinforces the oscillation and stimulates more molecules to flip.

I'll see if I can find the reference.  It was a very very long time ago. I recall a load of Hamiltonians and boards full of Dirac notation in a lecture in 1976 and thinking how cool that all sounded, but 24 GHz was a bit too esoteric for 18-year-old me adn I never made the connection with amateur radio stuff.

Thinking cap is on....

Neil G4DBN


Re: Observing the ammonia resonance

Andy G4JNT
 

A bit more from the Time Nuts Group
'''''''''''''''''''''''''''''''''''''''''''
As far as I recall there are two aspects to consider.
One is "low pressure" means vacuum pumps and pressure gauges calibrated
to ammonia (but any gauge and reasonable educated guess work will work
too), and if we want to make a permanent cell we need seal it... glass
or ceramic windows on the WG, plus all the rest to seal the in/out pipes
when we are happy with the ammonia pressure, otherwise it would be a
temporary experiment. Or leave the pumps and gas inlet running...

Second is that when the pressure is not too low absorption can be
intense but it is quite broad (thermal/collision broadening).
If we lower the pressure it will become sharper but less intense
or else we need more waveguide to get it deep enough.
Finding the good compromise is required hence the need to control the
ammonia pressure.

I don't remember anything in the 1Hz width... If my memory serves me
right I would say it was in the KHz region at half width, which should
be narrow enough to know where the center is within a few Hz...


Luis Cupido


On Mon, 20 Sept 2021 at 21:04, Robin Szemeti - G1YFG <robin@...> wrote:
A method of tracking the "dip" used in some other absorbtion resonance sensing systems (some HP rubidium vapour references I worked on at one point for example ) is to wobble the excitation frequency a little, say at 50Hz FM, with a deviation of a few Hz ... demodulate the output af the absorbtion cell in an AM demodulator ... if you are up the low side of the curve the demodulated 50Hz tone will be 180 degrees out of  phase with the driving signal  (as the frequency goes higher, more is absorbed, less output) .. if you are on the high side of the curve, the tone will be in phase with the driving signal ... this allows you to steer the centre frequency to the centre of the dip with a simple mixer circuit.

A further refinement to make sure you are centred on the dip can be to look at the 3rd harmonic of the demodulated signal. The FM modulated RF signal will be on the "cusp" of the absorption dip. This will produce a rise in the 3rd harmonic content of the AM demodulated signal, HP used a circuit to monitor the level of the 3rd harmonic and accurately keep the signal centred on the peak of the absorbtion band. I forget the precise details, but it was quite clever, and centred the RF within a few fractions of a Hertz on the rubidium absorbtion band.

On Mon, 20 Sept 2021 at 19:05, Andy G4JNT <andy.g4jnt@...> wrote:
On the Timenuts Group there's currently a discussion on, amongst other things, the ammonia resonance and it's possible use as a simpler frequency reference.
There is a narrow resonanance of the ammonia molecule at 23,870,129,007 Hz +/- 10 Hz  (ie just below our 24GHz band)

The resonance will be a Hz or so wide, and it ought to be possible to see this with relatively simple equipment.    First of all, get a length , several metres, of waveguide for 24GHz.   This needn't be 'proper' WG, just squashed water pipe will do to allow just the TE01 mode to propagate.    Fill this with ammonia (obvs. make the transitions gas tight)

Use an ADF5355 synth, and drive it's reference from a 48 bit DDS loike the AD9852.   Anything to be able to tune the 24GHz signal in sub-Hz steps, and to know what it is.   That chip will leak enough 4th harmonic from its VCO; launch this into the waveguide.   At the other end stick a 24GHz receiver tuned suitably.
Vary the input frequency a few Hz either side of the resonance and look for a dip.

One snag - if you use GPS locking, the residual variation of the GPSDO will cause it to drift across the resonance over a few tens of seconds.

Work out a way of feeding this dip back and controlling the synth reference in a locking loop and you have your own atomic frequency standard.   It's potentially  the same performance as cesium 

It seems in years gone by that caesium was possibly adopted instead of ammonia, simply because its resonance at 9.19GHz was easier to generate using ex-WW2 equipment that was 23GHz back in the 1940s when the first Cs standard was developed.


--
Robin Szemeti - G1YFG


Re: Round Table?

Robin Szemeti - G1YFG
 

There are much larger events running now (such as Southampton Boat Show, various concerts, the Telford Rally only a couple of weeks ago) our small gatherings are unlikely to have much impact, I think we are all big enough and ugly enough to make our own decisions if it is something we feel comfortable with, and with suitable sensibilities from those attending I think we can operate safely. Certainly a uWave round table would be a much smaller event than the Telford Hamfest!

Lets face it, if several hundred sweaty individuals are apparently fine to go jumping up and down in a night club and dribbling on each other for an evening, I'm sure we as sensible and careful individuals and somewhat more restrained adults can sort out a safe way of attending a well behaved round table, no?

Anyway, just food for thought. I would pleased to attend if something was available, and if there was a "take a covid test 24 hours before attending" mitigation or something similar, that would be fine by me ... I don't think the situation is going to change musch for the next couple of years, this is the new normal.


On Mon, 20 Sept 2021 at 20:55, Tom GM8MJV <tom@...> wrote:
Hi all


Would be nice - would travel for one but still concerns over the un-vaccinated and ability to be a carrier.

If need to show proof of double vaccinated different matter - or outsie.  Outside does have issues with our weather.

Tom
GM8MJV


On 20 Sep 2021, at 17:13, Robin Szemeti - G1YFG <robin@...> wrote:

Is there going to be a uWave round table any time soon?  Most activities seem to have returned for those wishing to run the gauntlet of the pox and I am keen to purchase more junk for my shed and meet with some old acquaintances.


--
Best regards,

Robin Szemeti

Redpoint Consulting Limited

E: robin@...
T: +44 (0) 1299 405028
M: +44 (0) 7971 883371

CONFIDENTIALITY NOTICE
The information contained in this e-mail is intended only for the
confidential use of the above named recipient. If you are not the
intended recipient or person responsible for delivering it to the
intended recipient, you have received this communication in error
and must not distribute or copy it.
Please accept the sender's apologies, notify the sender immediately
by return e-mail and delete this communication.

Thank you.

--
Robin Szemeti - G1YFG


--
Robin Szemeti - G1YFG


Re: Observing teh ammonia resonance

Robin Szemeti - G1YFG
 

A method of tracking the "dip" used in some other absorbtion resonance sensing systems (some HP rubidium vapour references I worked on at one point for example ) is to wobble the excitation frequency a little, say at 50Hz FM, with a deviation of a few Hz ... demodulate the output af the absorbtion cell in an AM demodulator ... if you are up the low side of the curve the demodulated 50Hz tone will be 180 degrees out of  phase with the driving signal  (as the frequency goes higher, more is absorbed, less output) .. if you are on the high side of the curve, the tone will be in phase with the driving signal ... this allows you to steer the centre frequency to the centre of the dip with a simple mixer circuit.

A further refinement to make sure you are centred on the dip can be to look at the 3rd harmonic of the demodulated signal. The FM modulated RF signal will be on the "cusp" of the absorption dip. This will produce a rise in the 3rd harmonic content of the AM demodulated signal, HP used a circuit to monitor the level of the 3rd harmonic and accurately keep the signal centred on the peak of the absorbtion band. I forget the precise details, but it was quite clever, and centred the RF within a few fractions of a Hertz on the rubidium absorbtion band.


On Mon, 20 Sept 2021 at 19:05, Andy G4JNT <andy.g4jnt@...> wrote:
On the Timenuts Group there's currently a discussion on, amongst other things, the ammonia resonance and it's possible use as a simpler frequency reference.
There is a narrow resonanance of the ammonia molecule at 23,870,129,007 Hz +/- 10 Hz  (ie just below our 24GHz band)

The resonance will be a Hz or so wide, and it ought to be possible to see this with relatively simple equipment.    First of all, get a length , several metres, of waveguide for 24GHz.   This needn't be 'proper' WG, just squashed water pipe will do to allow just the TE01 mode to propagate.    Fill this with ammonia (obvs. make the transitions gas tight)

Use an ADF5355 synth, and drive it's reference from a 48 bit DDS loike the AD9852.   Anything to be able to tune the 24GHz signal in sub-Hz steps, and to know what it is.   That chip will leak enough 4th harmonic from its VCO; launch this into the waveguide.   At the other end stick a 24GHz receiver tuned suitably.
Vary the input frequency a few Hz either side of the resonance and look for a dip.

One snag - if you use GPS locking, the residual variation of the GPSDO will cause it to drift across the resonance over a few tens of seconds.

Work out a way of feeding this dip back and controlling the synth reference in a locking loop and you have your own atomic frequency standard.   It's potentially  the same performance as cesium 

It seems in years gone by that caesium was possibly adopted instead of ammonia, simply because its resonance at 9.19GHz was easier to generate using ex-WW2 equipment that was 23GHz back in the 1940s when the first Cs standard was developed.


--
Robin Szemeti - G1YFG


Re: Observing the ammonia resonance

Andy G4JNT
 

Don't know any of the physics but I doubt air would give a problem.   The absorption is specific to the ammonia and should be unaffected by impurities that don't impede microwave propagation.  You may get extra resonances, but they'll be way-removed from 24GHz, let alone the narrow resonance band.

The Time Nuts thread have cited some references, but they're scanned-in books that'll need some study - and I don't like reading books on line !



On Mon, 20 Sept 2021 at 20:38, Barry Chambers <b.chambers@...> wrote:

Hi Andy

an intruiging project. Any idea of the gas pressure in the waveguide? Presumably you have to get rid of the air first?

73 Barry G8AGN


On 20/09/2021 19:06, Andy G4JNT wrote:
Oh dear, if anyone replies, please clean-up my typo in the subject line :-(
(Done here)



On Mon, 20 Sept 2021 at 19:04, Andy Talbot <andy.g4jnt@...> wrote:
On the Timenuts Group there's currently a discussion on, amongst other things, the ammonia resonance and it's possible use as a simpler frequency reference.
There is a narrow resonanance of the ammonia molecule at 23,870,129,007 Hz +/- 10 Hz  (ie just below our 24GHz band)

The resonance will be a Hz or so wide, and it ought to be possible to see this with relatively simple equipment.    First of all, get a length , several metres, of waveguide for 24GHz.   This needn't be 'proper' WG, just squashed water pipe will do to allow just the TE01 mode to propagate.    Fill this with ammonia (obvs. make the transitions gas tight)

Use an ADF5355 synth, and drive it's reference from a 48 bit DDS loike the AD9852.   Anything to be able to tune the 24GHz signal in sub-Hz steps, and to know what it is.   That chip will leak enough 4th harmonic from its VCO; launch this into the waveguide.   At the other end stick a 24GHz receiver tuned suitably.
Vary the input frequency a few Hz either side of the resonance and look for a dip.

One snag - if you use GPS locking, the residual variation of the GPSDO will cause it to drift across the resonance over a few tens of seconds.

Work out a way of feeding this dip back and controlling the synth reference in a locking loop and you have your own atomic frequency standard.   It's potentially  the same performance as cesium 

It seems in years gone by that caesium was possibly adopted instead of ammonia, simply because its resonance at 9.19GHz was easier to generate using ex-WW2 equipment that was 23GHz back in the 1940s when the first Cs standard was developed.

-- 
73
Barry, G8AGN


Re: Round Table?

Tom GM8MJV
 

Hi all


Would be nice - would travel for one but still concerns over the un-vaccinated and ability to be a carrier.

If need to show proof of double vaccinated different matter - or outsie.  Outside does have issues with our weather.

Tom
GM8MJV


On 20 Sep 2021, at 17:13, Robin Szemeti - G1YFG <robin@...> wrote:

Is there going to be a uWave round table any time soon?  Most activities seem to have returned for those wishing to run the gauntlet of the pox and I am keen to purchase more junk for my shed and meet with some old acquaintances.


--
Best regards,

Robin Szemeti

Redpoint Consulting Limited

E: robin@...
T: +44 (0) 1299 405028
M: +44 (0) 7971 883371

CONFIDENTIALITY NOTICE
The information contained in this e-mail is intended only for the
confidential use of the above named recipient. If you are not the
intended recipient or person responsible for delivering it to the
intended recipient, you have received this communication in error
and must not distribute or copy it.
Please accept the sender's apologies, notify the sender immediately
by return e-mail and delete this communication.

Thank you.

--
Robin Szemeti - G1YFG


Re: Observing the ammonia resonance

Barry Chambers
 

Hi Andy

an intruiging project. Any idea of the gas pressure in the waveguide? Presumably you have to get rid of the air first?

73 Barry G8AGN


On 20/09/2021 19:06, Andy G4JNT wrote:
Oh dear, if anyone replies, please clean-up my typo in the subject line :-(
(Done here)



On Mon, 20 Sept 2021 at 19:04, Andy Talbot <andy.g4jnt@...> wrote:
On the Timenuts Group there's currently a discussion on, amongst other things, the ammonia resonance and it's possible use as a simpler frequency reference.
There is a narrow resonanance of the ammonia molecule at 23,870,129,007 Hz +/- 10 Hz  (ie just below our 24GHz band)

The resonance will be a Hz or so wide, and it ought to be possible to see this with relatively simple equipment.    First of all, get a length , several metres, of waveguide for 24GHz.   This needn't be 'proper' WG, just squashed water pipe will do to allow just the TE01 mode to propagate.    Fill this with ammonia (obvs. make the transitions gas tight)

Use an ADF5355 synth, and drive it's reference from a 48 bit DDS loike the AD9852.   Anything to be able to tune the 24GHz signal in sub-Hz steps, and to know what it is.   That chip will leak enough 4th harmonic from its VCO; launch this into the waveguide.   At the other end stick a 24GHz receiver tuned suitably.
Vary the input frequency a few Hz either side of the resonance and look for a dip.

One snag - if you use GPS locking, the residual variation of the GPSDO will cause it to drift across the resonance over a few tens of seconds.

Work out a way of feeding this dip back and controlling the synth reference in a locking loop and you have your own atomic frequency standard.   It's potentially  the same performance as cesium 

It seems in years gone by that caesium was possibly adopted instead of ammonia, simply because its resonance at 9.19GHz was easier to generate using ex-WW2 equipment that was 23GHz back in the 1940s when the first Cs standard was developed.

-- 
73
Barry, G8AGN


Observing the ammonia resonance

Andy G4JNT
 

Oh dear, if anyone replies, please clean-up my typo in the subject line :-(
(Done here)



On Mon, 20 Sept 2021 at 19:04, Andy Talbot <andy.g4jnt@...> wrote:
On the Timenuts Group there's currently a discussion on, amongst other things, the ammonia resonance and it's possible use as a simpler frequency reference.
There is a narrow resonanance of the ammonia molecule at 23,870,129,007 Hz +/- 10 Hz  (ie just below our 24GHz band)

The resonance will be a Hz or so wide, and it ought to be possible to see this with relatively simple equipment.    First of all, get a length , several metres, of waveguide for 24GHz.   This needn't be 'proper' WG, just squashed water pipe will do to allow just the TE01 mode to propagate.    Fill this with ammonia (obvs. make the transitions gas tight)

Use an ADF5355 synth, and drive it's reference from a 48 bit DDS loike the AD9852.   Anything to be able to tune the 24GHz signal in sub-Hz steps, and to know what it is.   That chip will leak enough 4th harmonic from its VCO; launch this into the waveguide.   At the other end stick a 24GHz receiver tuned suitably.
Vary the input frequency a few Hz either side of the resonance and look for a dip.

One snag - if you use GPS locking, the residual variation of the GPSDO will cause it to drift across the resonance over a few tens of seconds.

Work out a way of feeding this dip back and controlling the synth reference in a locking loop and you have your own atomic frequency standard.   It's potentially  the same performance as cesium 

It seems in years gone by that caesium was possibly adopted instead of ammonia, simply because its resonance at 9.19GHz was easier to generate using ex-WW2 equipment that was 23GHz back in the 1940s when the first Cs standard was developed.


Observing teh ammonia resonance

Andy G4JNT
 
Edited

On the Timenuts Group there's currently a discussion on, amongst other things, the ammonia resonance and its possible use as a simpler frequency reference.
There is a narrow resonannce of the ammonia molecule at 23,870,129,007 Hz +/- 10 Hz  (ie just below our 24GHz band)
 
The resonance will be a Hz or so wide, and it ought to be possible to see this with relatively simple equipment.    First of all, get a length , several metres, of waveguide for 24GHz.   This needn't be 'proper' WG, just squashed water pipe will do to allow just the TE01 mode to propagate.    Fill this with ammonia (obvs. make the transitions gas tight)
 
Use an ADF5355 synth, and drive its reference from a 48 bit DDS like the AD9852.   Anything to be able to tune the 24GHz signal in sub-Hz steps, and to know what it is.   That chip will leak enough 4th harmonic from its VCO; launch this into the waveguide.   At the other end stick a 24GHz receiver tuned suitably.
Vary the input frequency a few Hz either side of the resonance and look for a dip.
 
One snag - if you use GPS locking, the residual variation of the GPSDO will cause it to drift across the resonance over a few tens of seconds.
 
Work out a way of feeding this dip back and controlling the synth reference in a locking loop and you have your own atomic frequency standard.   It's potentially  the same performance as cesium 
 
It seems in years gone by that caesium was possibly adopted instead of ammonia, simply because its resonance at 9.19GHz was easier to generate using ex-WW2 equipment that was 23GHz back in the 1940s when the first Cs standard was developed.
 
Andy
 


Re: Chip supplies have hit JNT Labs

Colin G4EML
 

You sometimes have to select ‘other payment options’ before it appears. 

Colin. 


On 20 Sep 2021, at 18:15, Gedas <w8bya@...> wrote:

Oh how interesting. I tried to purchase some uW terminations a month ago and the only payment option was a CC. I did not see PP anywhere. Knowing what you just said I will look much more carefully.....or maybe I was not on the "real" AliExpress site.....TU 73

Gedas, W8BYA EN70JT

Gallery at http://w8bya.com (under repair)
Light travels faster than sound....
This is why some people appear bright until you hear them speak.
On 9/20/2021 12:26 PM, Colin G4EML wrote:

Yes, I always use Paypal with AliExpress. 

 

They actually have some quite good safety features.  You are actually dealing with individual sellers but your payment goes to AliExpress and they don’t transfer the money to the sellers until you have received the goods and confirmed receipt.

If for some reason the seller doesn’t send the goods in the agreed time or the goods don’t arrive you automatically get refunded.  

That happened to me once. The seller didn’t dispatch within the promised 10 days and I got an automatic refund.

Other than that I have had quite a few successful purchases.

 

Colin G4EML

 

 

 

 

 

 

 

 

From: Gedas
Sent: 20 September 2021 16:24
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] Chip supplies have hit JNT Labs

 

Hi Colin. Have you been able to pay using PayPal with AliExpress? I am extremely reluctant to hand over my personal credit card info to them. At least with PP I have some safety. 73

Gedas, W8BYA EN70JT
 
Gallery at http://w8bya.com (under repair)
Light travels faster than sound....
This is why some people appear bright until you hear them speak.

On 9/20/2021 8:56 AM, Colin G4EML wrote:

AliExpress is still showing a few people who claim to have some available. 

I am nervous about ordering chips from China but I recently needed some 16F1825s urgently and that was the only place I could get them. They arrived and proved to be OK. 

 

Colin G4EML. 

 


On 20 Sep 2021, at 13:44, Andy G4JNT <andy.g4jnt@...> wrote:

Yes, was meant to be 12F617

 

Andy

 

 

 

On Mon, 20 Sept 2021 at 13:39, Robin Szemeti - G1YFG <robin@...> wrote:

Is 12F167 a typo?

 

 

 


Re: Chip supplies have hit JNT Labs

Gedas
 

Oh how interesting. I tried to purchase some uW terminations a month ago and the only payment option was a CC. I did not see PP anywhere. Knowing what you just said I will look much more carefully.....or maybe I was not on the "real" AliExpress site.....TU 73

Gedas, W8BYA EN70JT

Gallery at http://w8bya.com (under repair)
Light travels faster than sound....
This is why some people appear bright until you hear them speak.
On 9/20/2021 12:26 PM, Colin G4EML wrote:

Yes, I always use Paypal with AliExpress. 

 

They actually have some quite good safety features.  You are actually dealing with individual sellers but your payment goes to AliExpress and they don’t transfer the money to the sellers until you have received the goods and confirmed receipt.

If for some reason the seller doesn’t send the goods in the agreed time or the goods don’t arrive you automatically get refunded.  

That happened to me once. The seller didn’t dispatch within the promised 10 days and I got an automatic refund.

Other than that I have had quite a few successful purchases.

 

Colin G4EML

 

 

 

 

 

 

 

 

From: Gedas
Sent: 20 September 2021 16:24
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] Chip supplies have hit JNT Labs

 

Hi Colin. Have you been able to pay using PayPal with AliExpress? I am extremely reluctant to hand over my personal credit card info to them. At least with PP I have some safety. 73

Gedas, W8BYA EN70JT
 
Gallery at http://w8bya.com (under repair)
Light travels faster than sound....
This is why some people appear bright until you hear them speak.

On 9/20/2021 8:56 AM, Colin G4EML wrote:

AliExpress is still showing a few people who claim to have some available. 

I am nervous about ordering chips from China but I recently needed some 16F1825s urgently and that was the only place I could get them. They arrived and proved to be OK. 

 

Colin G4EML. 

 


On 20 Sep 2021, at 13:44, Andy G4JNT <andy.g4jnt@...> wrote:

Yes, was meant to be 12F617

 

Andy

 

 

 

On Mon, 20 Sept 2021 at 13:39, Robin Szemeti - G1YFG <robin@...> wrote:

Is 12F167 a typo?

 

 

 


Re: Chip supplies have hit JNT Labs

Colin G4EML
 

Yes, I always use Paypal with AliExpress. 

 

They actually have some quite good safety features.  You are actually dealing with individual sellers but your payment goes to AliExpress and they don’t transfer the money to the sellers until you have received the goods and confirmed receipt.

If for some reason the seller doesn’t send the goods in the agreed time or the goods don’t arrive you automatically get refunded.  

That happened to me once. The seller didn’t dispatch within the promised 10 days and I got an automatic refund.

Other than that I have had quite a few successful purchases.

 

Colin G4EML

 

 

 

 

 

 

 

 

From: Gedas
Sent: 20 September 2021 16:24
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] Chip supplies have hit JNT Labs

 

Hi Colin. Have you been able to pay using PayPal with AliExpress? I am extremely reluctant to hand over my personal credit card info to them. At least with PP I have some safety. 73

Gedas, W8BYA EN70JT
 
Gallery at http://w8bya.com (under repair)
Light travels faster than sound....
This is why some people appear bright until you hear them speak.

On 9/20/2021 8:56 AM, Colin G4EML wrote:

AliExpress is still showing a few people who claim to have some available. 

I am nervous about ordering chips from China but I recently needed some 16F1825s urgently and that was the only place I could get them. They arrived and proved to be OK. 

 

Colin G4EML. 

 


On 20 Sep 2021, at 13:44, Andy G4JNT <andy.g4jnt@...> wrote:

Yes, was meant to be 12F617

 

 

 

On Mon, 20 Sept 2021 at 13:39, Robin Szemeti - G1YFG <robin@...> wrote:

Is 12F167 a typo?

 

 

 


Round Table?

Robin Szemeti - G1YFG
 

Is there going to be a uWave round table any time soon?  Most activities seem to have returned for those wishing to run the gauntlet of the pox and I am keen to purchase more junk for my shed and meet with some old acquaintances.


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Redpoint Consulting Limited

E: robin@...
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M: +44 (0) 7971 883371

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Re: Chip supplies have hit JNT Labs

Gedas
 

Hi Colin. Have you been able to pay using PayPal with AliExpress? I am extremely reluctant to hand over my personal credit card info to them. At least with PP I have some safety. 73

Gedas, W8BYA EN70JT

Gallery at http://w8bya.com (under repair)
Light travels faster than sound....
This is why some people appear bright until you hear them speak.
On 9/20/2021 8:56 AM, Colin G4EML wrote:

AliExpress is still showing a few people who claim to have some available. 
I am nervous about ordering chips from China but I recently needed some 16F1825s urgently and that was the only place I could get them. They arrived and proved to be OK. 

Colin G4EML. 


On 20 Sep 2021, at 13:44, Andy G4JNT <andy.g4jnt@...> wrote:

Yes, was meant to be 12F617



On Mon, 20 Sept 2021 at 13:39, Robin Szemeti - G1YFG <robin@...> wrote:
Is 12F167 a typo?



Re: Chip supplies have hit JNT Labs

Neil Smith G4DBN
 

There is a search box for package type and in-stock and loads more parameters.
Neil G4DBN

On 20 Sep 2021 13:49, Andy G4JNT <andy.g4jnt@...> wrote:
Interesting - haven't met Octopart before

Unfortunately it doesn't help with package type.   The companies it says have 12F167 devices only have them in QFN now.  And that is really one package I'd prefer not to use unless essential!



On Mon, 20 Sept 2021 at 13:39, Robin Szemeti - G1YFG <robin@...> wrote:
Try putting your part numbers into http://octopart.com  saves a lot of searching.



Re: Chip supplies have hit JNT Labs

Robin Szemeti - G1YFG
 

You can build entire part lists in Octopart, store them away etc, very handy.  We basically build Octopart lists for all our stuff these days, saves a lot of hassle.


On Mon, 20 Sept 2021 at 13:49, Andy G4JNT <andy.g4jnt@...> wrote:
Interesting - haven't met Octopart before

Unfortunately it doesn't help with package type.   The companies it says have 12F167 devices only have them in QFN now.  And that is really one package I'd prefer not to use unless essential!



On Mon, 20 Sept 2021 at 13:39, Robin Szemeti - G1YFG <robin@...> wrote:
Try putting your part numbers into http://octopart.com  saves a lot of searching.


--
Robin Szemeti - G1YFG

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