Re: Tests on HP 4342A Q Meter and more
Hi Ed,
Thanks for your good comments.? I wanted to try making my own transformer but I realized that it was not so easy !
I should try your suggestions on my transformers.
Yes, I have a 4342A? Q Meter, bought from my employer about 25 years ago.
Back in the early seventies I did some research to develop a custom Q meter for my employer.
It had to cover from 1 KHz to 5 MHz. And yes, the transformer injection method was used as in the HP4342A.
I used a very high mu tape core which worked well down to 1 KHz.
Getting the low impedance drive (less than 5 milliohms) was difficult at the higher frequencies.
I found that I had to use a large copper strip at the secondary. I believe that the tape core
essentially "disappeared" at the higher frequencies, leaving only a low ESR strip.
I also tried to use the LC circuit under test as an oscillator to generate the test signal.
A broadband amplifier with an AGC was used.? It monitored the drive voltage and kept it constant.
This was done with a 400EL voltmeter, using the DC output to provide feedback for the AGC.
The Q is then read on the RF voltmeter across the LC circuit.
The oscillator needs to have 360 degrees phase shift to work properly.
The first 180 degrees is easy.? The LC circuit will provide 90 degrees phase shift at resonance.
This means that another 90 degrees of phase shift needs to be provided externally.
Ideally it should be a broadband phase shifter and possibly require a fine tuning at high Q and higher RF frequencies.
I did a prototype of this scheme that worked in the X10 KHz range back then, for my employer.
It was fun !? But the project didn't go any further.
Jacques
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Re: Tests on HP 4342A Q Meter and more
Stabilizing the excitation voltage via a feedback
loop is quite a common feature of many RF signal generators.? Look at
Marconi 2022 for example.? This uses hot carrier diode detector to monitor
the voltage and a pin diode attenuator to control its level via a feedback amp.
I have been looking at modernizing the Boonton 250 RX
meter.? This uses a Schering bridge circuit driven by wide band
transformer supplying two equal but anti-phase excitations to each side of the
bridge circuit.? To achieve bridge balance it is essential to keep these
two voltages equal over the full frequency range ( 100KHz to 250MHz for the
Boonton 250)
One way to maintain excitation balance is to make the
source impedance of the transformer outputs very low.? Another way is to
incorporate feedback control loops.? I have had moderate success using Schotty
barrier diodes HSMS-2822 detectors and BAP64Q pin diode attenuators. I needed
to pump the signal level up to allow for the attenuation but this is easy with
a MMIC amp using GALI-39s.? This gave levelling vs freq of 0.5dB from 1 -
300MHz.
Circuit complexity is not great but this approach
leaves the way open to digitally modifying the excitation voltages depending on
DDS generated primary excitation source.
There are some other ideas in this project associated
with how to minimize stray inductance and capacitance in the balance controls
and if it is possible to replace these variable air caps with some voltage
controlled varicap diodes (see MA46410 ).
Lots of opportunities to play with new ideas here but
for me, maybe not enough time left.
?
Bill
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Re: Tests on HP 4342A Q Meter and more
Hi Jacques and Mikek, As you can see, I have joined the group.
Jacques, I enjoyed reading your report on this stuff. You really dug deep and figured out a lot. Nice work. One thing I wonder is that if you already have a 4342A, are you investigating it to improve it, to build your own version of a Q-meter, or just for fun?
I have some suggestions on improving the transformer performance, involving the primary only at this point. The secondary gets to be tricky due to the large impedance ratio, I'll talk about that another time. The first thing is to set up the primary winding structure to be one clean, uniform layer that completely fills (no gaps between the passes through the center) the toroid surface. The beginning and end of the winding should be touching. This can be done in a number of ways, like with different core sizes, wire gauge, and number of turns. For instance, with either experimental transformer, it looks like there's maybe 10-15 percent unfilled. Keeping the same wire gauge, you could say just put on more turns until it's filled. This would change the ratio, of course, but as I understand, the 50 turns is a numerical convenience, so it should be possible to use any number, within reason, and adjust the scaling to accommodate it. You could also go with bigger wire instead, chosen to land near the desired number of turns, and fully filled. Bigger wire would reduce losses a bit, while achieving full-fill helps to minimize the leakage inductance.
Now that you have both ends of the winding at the same spot, the next thing is to twist them tightly together over their whole length, and let them exit the transformer as a transmission line. Some sleeving will help keep them together and protected. The trip to the driver amplifier should be as short as possible, where the ends are allowed to separate for making connections. This form of wiring further reduces the leakage inductance by keeping everything close-in to the core, and minimizing the loop area of the interconnect lines.
Ed
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Re: Tests on HP 4342A Q Meter and more
On Sat, Jan 21, 2023 at 11:45 AM, Jacques Audet wrote:
I just did some simple simulations and yes it would certainly help to stabilize the 30 mV drive voltage.
Then the Rs value doesn't matter, as you wrote.
Even a blind squirrel can find a nut once in a while. :-)
>In all cases a feedback circuit could be designed and would add complexity. The complexity is over my ability, I sometimes see the big picture and even a block diagram, but can't design. Yes, but once designed, it's done, I don't know if the complexity is all that much, but again, I have no design ability. Re: the negative effect of reactance of the drive transformer. I haven't understood, how the reactance affects the measurement as long as the Drive voltage remains at 30mV. Maybe the problem is in the nature of the feedback required to keep it at 30mV, as Frequency changes, when reactance is involved. I'm sure you're aware, but a change in Rs also will cause the drive voltage to sag with High Q tests and rise with low Q tests because of the Rsource resistance. This is where I started to see the problem I thought could be corrected with feedback. I wanted to use the transformer output voltage to correct the non-linearity issues of the Transformer. ? I'm still not seeing how the Reactance prevents this, but that's my problem, just a lack of knowledge. (if I was 18 again, I would do education differently) ??????????????????????????????????????????????????? Keep up the work, I enjoy the time trying to understand, Mikek
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Re: Tests on HP 4342A Q Meter and more
Hi Mikek,
I just did some simple simulations and yes it would certainly help to stabilize the 30 mV drive voltage.
Then the Rs value doesn't matter, as you wrote.
In the case of the HP4342A, at worst case, the required? voltage drive will have to be increased? by a factor of 12 at 50 MHz.
This is because the source resistance increases at 130 milliohm at 50 MHz as well as the source reactance which increases to approx. 1 ohm.
If the source resistance can be kept low, like 20 milliohm and the source inductance at 0.5 nH, then the required? voltage drive
will have to be increased? by a factor of only 2 at 50 MHz, to keep the effective drive voltage constant.
In my document I have shown how to build such a resistor.
You may verify that the source voltage dips down at resonance by monitoring the drive voltage at higher frequencies and high tuning cap values.
The attached document shows the two cases, at 50 MHz.
In all cases a feedback circuit could be designed and would add complexity.
The second option requires monitoring the source drive voltage with an RF voltmeter (Boonton or Fluke 8920A - max 20 MHz), and adjusting
the drive to keep a constant voltage after peaking at resonance. The Boonton 4200 has a DC out which could be used for feedback to
a voltage controlled attenuator.
The third option requires calculating the error generated by the source Rs and Ls.? My Excel document only compensates for Rs but it
should be possible to add the effect of the source Ls.
The fourth option would be to measure both voltages and compute the ratio, so that you don't need to stabilize the drive voltage.
I have an RF voltmeter/dB meter in development that does ratio, but it is very slow in this mode. Too slow for finding a maximum.
Food for thinking !
Jacques,
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Re: Tests on HP 4342A Q Meter and more
Hi Jacques,
? I've been beating this dead horse for a while, but your figure on page 23 of the Rs curve over frequency of the drive transformer, makes my point.
The drive level will change with frequency and it will also change with load.
So, why not monitor the 30mV, feed it back to the oscillator to adjust the level to keep drive on the DUT at 30mv to overcome drive voltage changes that occur with frequency and load. Then Rs doesn't matter.
You will need a ganged switch at the osc output and to set the Q meter FS to set different Q levels.
?The design is over my abilities, but if we get a design, I can build it.
???????????????????????????????????? Thanks for all your input, Mikek
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Re: Fabry-Perot Open Resonator for mmwave dielectric measurements
You might want to pose this question on this forum. There are quite a few antenna experts there.
/g/antenna-research/topics
Don Bitters
On Sat, Jan 14, 2023 at 5:57 PM, Neil Smith G4DBN <neil@...> wrote: Hi folks, does anyone have experience of a Fabry-Perot Open Resonator for dielectric solid and fluid characterisation at microwave/mmwave?
I want to build one (!) but not simply copy how it's been done before. Ideas about aperture feed arrangements, spherical mirror dimensions and focal length and the pros/cons of the lower mirror being planar would he helpful. Sort of an etalon for radio type of thing.
Application is measuring the permittivity and loss tangent of dielectric sheets and thin layers of dielectric fluids at 20 to 120 GHz.
Initial use case is measuring the performance of 3D printed dielectrics (Filament filled with TiO2 or UV resin filled with ceramic particles). I'm also making some split-post dielectric resonators for low frequencies sub-20 GHz, but if I can find suitable dielectric resonator pucks for 24GHz it would be useful to have both types to cross-calibrate them. Another project in my pipeline is a set of waveguide cavity perturbation fixtures for characterising thin dielectric rods. Someone buy me a PNA-X please.
Neil
|
Fabry-Perot Open Resonator for mmwave dielectric measurements
Hi folks, does anyone have experience of a Fabry-Perot Open Resonator for dielectric solid and fluid characterisation at microwave/mmwave?
I want to build one (!) but not simply copy how it's been done before. Ideas about aperture feed arrangements, spherical mirror dimensions and focal length and the pros/cons of the lower mirror being planar would he helpful. Sort of an etalon for radio type of thing.
Application is measuring the permittivity and loss tangent of dielectric sheets and thin layers of dielectric fluids at 20 to 120 GHz.
Initial use case is measuring the performance of 3D printed dielectrics (Filament filled with TiO2 or UV resin filled with ceramic particles). I'm also making some split-post dielectric resonators for low frequencies sub-20 GHz, but if I can find suitable dielectric resonator pucks for 24GHz it would be useful to have both types to cross-calibrate them. Another project in my pipeline is a set of waveguide cavity perturbation fixtures for characterising thin dielectric rods. Someone buy me a PNA-X please.
Neil
|
Re: Another variable to consider
"Imagine that one day you wake up to learn that all the GPS satellites have been destroyed. What's happening? War? Super-massive solar flare? Whatever it is you probably won't be spending the afternoon in your electronics hobby area. In all my years of playing with GPS it has never been "off the air." So, as a hobbyist, do you really need a GPS standard with "hold-over" that learns the properties of your oscillator and corrects the oscillator even when GPS is not present? (Hint: nope.) So why spend an inordinate amount of time and effort giving your standard a hold-over function you can only appreciate by physically disconnecting the GPS antenna? This unit provides an excellent 10 MHz reference as long as an accurate 1PPs is supplied by the GPS receiver. When GPS goes down you should be brushing up on your hunter-gatherer skills anyway."
I work in a building where we have a GPS repeater because otherwise you can't get GPS signal for some of the things we repair. The makerspace I belong to is in a similar all-metal building where you can't get a GPS signal in many locations in the building.
I've been in many buildings where I can't get a GPS satellite. My home is one of those places.
Steve Greenfield AE7HD
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Re: True RMS-Millivoltmeter
Norbert,
Do you have 274-X Gerber files for this project?
Sam W3OHM
Hello all,
some years ago I developed together with Georg (DL6GL) a very precise True RMS-Millivoltmeter.
Under the above link you can find all relevant data of the instrument.
Kind regards
Norbert, DG1KPN
|
Hello all,
some years ago I developed together with Georg (DL6GL) a very precise True RMS-Millivoltmeter.
Under the above link you can find all relevant data of the instrument.
Kind regards
Norbert, DG1KPN
|
Re: Another variable to consider
Change of frequency with orientation is a? well known property of
quartz resonators and is a function of how the crystal is
suspended , there are six axis of interest x,y & z up or
down.? It has absolutely nothing to do with relativity and
absolutely everything to do with the crystal? mounting design and
manufacture. Frequency change with orientation is a datasheet
parameter for very good oscillators.
Jeff's oscillator is a $30 surplus item from China as a pull. The
HP 53220A measures frequency by the? reciprocal method, it
measures the period of a set of cycles, then calculates the
average. It costs about a hundred times as much as the second hand
oscillator. Ultimately you are getting the frequency ratio to the
counter's internal clock, it can be a good or excellent free
running oscillator or preferably a house standard that is GPS
referenced.
Most double oven oscillators use AT cut crystals. You can get
higher performance by using a SC cut crystal? in a modern single
oven which runs at a higher temperature. Second hand oscillators
from China are very cheap but they may have had a hard time which
can degrade their after life, it's a lottery with cheap tickets.
Always a risk that with very fine electronic tuning the package
may be sealed and the crystal has drifted beyond correction.
There are no great problems in comparing good crystal
oscillators, any dual trace scope will do, alternately a double
balanced mixer and a voltmeter will show the phase difference.
Better schemes use dual mixing down to a very low frequency but
all schemes need a good local reference which is usually a GPS
based standard.
A GPS disciplined oscillator is a very useful use for a surplus
xtal oscillator, there are many designs on the web. A very elegant
design was produced by Charles Wenzel using a simple PLL and a
cheap GPS module, it's here
Regards,
Alan G8LCO.
|
Re: Another variable to consider
Jeff take a look at the ke5fx website?
Pete G4GJL
From:
.
?
"At the equator, the circumference of the Earth is 40,070 kilometers, and the day is 24 hours long so the speed is 1670 kilometers/hour ( 1037 miles/hr). This decreases by the cosine of your latitude so that at a latitude of 45 degrees, cos(45) = .707 and the speed is .707 x 1670 = 1180 kilometers/hr. You can use this formula to find the speed of rotation at any latitude."
?
Lexington is on the 38 parallel. The 38 parallel actually transects Lexington.
?
cos(38) = 0.7880107536
?
0.788 X 1180km/hr = 929.84km/hr
= 929840 meters per hour in an east to west vector.
?
929840 / 3600 = 258.289 meters per second.
The earth's gravity is ~980cm/second, 0.98 meters per second.
?
I'll have to see if rotating the oscillator 45 degrees east then west produces, then north and south and see if there are different frequency shifts.
?
Of course the angular velocity is steady so probably has no effect.
?
The lab ceilings are ~12 feet high, I wonder if, while keeping the oscillator as level as practical, and checking the frequency at floor level then ceiling level will have any effect. I doubt it.
?
It's late and the decrease in gravity caused by a 12 foot change in elevation will get into silly small numbers. I'll do the test and only if there is a change will I work out the math.
?
I might be able to design an experiment that will get me 3 credit hours of independent study.
Somewhere I have the velocity and vectors of the motion of the earth around the sun and as our solar systems screams on the outer edge of the Milky Way.
|
Re: Another variable to consider
On Mon, 9 Jan 2023 at 01:49, Tom Lee < tomlee@...> wrote:
Hi Robin,
If by relativistic effect you were alluding to gravitational
redshift, the answer is no, this wouldn't fit. You'd expect this
observed magnitude of shift only with a multiple-thousands of
kilometer change in altitude.
The signals from GPS satellites at 20,000km altitude undergo a
blueshift of about a half ppb or so.
-- Cheers
Tom
Tom, who runs has climbed mountains with Cs clocks
That’s a great website. His atomic wristwatch is nice too
It will drift less a ns until the battery is flat.
I thought that I had read on the mailing list about clocks changing as they are moved up/down a room. But those guys have clocks a wee bit better than a double oven OCXO. Several list members have hydrogen masers and I think at least half have Cs clocks.?
Dave
-- Dr. David Kirkby, Kirkby Microwave Ltd, drkirkby@...Telephone 01621-680100./ +44 1621 680100 Registered in England & Wales, company number 08914892. Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, Chelmsford, Essex, CM3 6DT, United Kingdom
|
Re: Another variable to consider
You might want to take a look at the original paper by Pound and
Rebka (
is a good start). You'll see what they needed in order to make a
reasonable measurement within their constrained lab equipment (which
included a not-very-tall tower on Harvard's campus).
Also, reading Tom Van Baak's saga is a must:
That will help calibrate you a
little further on what you need.
Short summary: A couple of cesium clocks, many batteries, and Mt.
Rainier = family fun while testing Einstein.
--Tom
--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
420 Via Palou Mall
Stanford University
Stanford, CA 94305-4070
On 1/8/2023 18:08, Jeff Green wrote:
toggle quoted message
Show quoted text
From:
.
?
"At the
equator, the circumference of the Earth is 40,070
kilometers, and the day is 24 hours long so the speed is
1670 kilometers/hour ( 1037 miles/hr). This decreases by
the cosine of your latitude so that at a latitude of 45
degrees, cos(45) = .707 and the speed is .707 x 1670 =
1180 kilometers/hr. You can use this formula to find the
speed of rotation at any latitude."
?
Lexington is on the 38 parallel.
The 38 parallel actually transects Lexington.
?
cos(38) = 0.7880107536
?
0.788 X 1180km/hr = 929.84km/hr
= 929840 meters per hour in an east to west vector.
?
929840 / 3600 = 258.289 meters per second.
The
earth's gravity is ~980cm/second, 0.98 meters per second.
?
I'll have to see if rotating the oscillator 45 degrees
east then west produces, then north and south and see if there
are different frequency shifts.
?
Of course the angular velocity is steady so probably
has no effect.
?
The lab ceilings are ~12 feet high, I wonder if, while
keeping the oscillator as level as practical, and checking the
frequency at floor level then ceiling level will have any
effect. I doubt it.
?
It's late and the decrease in gravity caused by a 12
foot change in elevation will get into silly small numbers.
I'll do the test and only if there is a change will I work out
the math.
?
I might be able to design an experiment that will get
me 3 credit hours of independent study.
Somewhere I have the velocity and vectors of the motion of the
earth around the sun and as our solar systems screams on the
outer edge of the Milky Way.
|
Re: Another variable to consider
Hi Robin,
If by relativistic effect you were alluding to gravitational
redshift, the answer is no, this wouldn't fit. You'd expect this
observed magnitude of shift only with a multiple-thousands of
kilometer change in altitude.
The signals from GPS satellites at 20,000km altitude undergo a
blueshift of about a half ppb or so.
-- Cheers
Tom
--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
420 Via Palou Mall
Stanford University
Stanford, CA 94305-4070
On 1/8/2023 17:30, G8DQX list wrote:
toggle quoted message
Show quoted text
Jeff,
if you imagine gravity as a force vector going through the
crystal in the oscillator, you can imagine a minute
deformation of the crystal as the vector is rotated through 90°.
That deformation gives rise to, as you report, mHz variation in
10?MHz, or parts in 10-10. That's pretty good to be
able to measure.
Full disclosure: I've not done the thinking to check that it
could not be considered a relativistic effect. The effect would
be around 1 in 10-9 for Earth's surface gravity,
subject to finding a credible vectorial mechanism. [Best to
check the 10-9.]
We're now in serious physics experimenter territory, allowing
for all the uncertainties and experimental errors in what one is
measuring. Well, Scotty, we can measure it, but what exactly
are we measuring?
73, Stay Safe,
Robin, G8DQX
On 08/01/2023 21:48, Jeff Green
wrote:
Friday
afternoon the instrumentation and laboratory supervisor
showed me an aspect of measurement uncertainty I'd never
heard of.
She used
an new Keysight 53220A 13 digit
frequency
counter and my "?UTC 108663
MY3109 NOX038663XS 10MHz 10.0MHZ OCXO Double Oven Ultra
Precision oscukkatir:
?
New ultra
precision, high quality UCT 10MHz Double Oven OCXO crystal
oscillator
?
…They
trim to 10.0000000.X MHz and hold it for days at a time in a
regular room with no special temperature control. The room is
typical shirt sleeve environment.
With the
above as background.
?
The lab
supervisor had asked me to bring in an oscillator and we let
it run overnight.
?
We trimmed
the oscillator to read 10.00000000000MHz.
When she
rotated the oscillator it shifted a few milihertz but
returned to exactly
10.00000000000MHz
when placed in the original plane.
?
?
?
?
?
I found an online video which
demonstrates this oddity:
|
Re: Another variable to consider
Jeff,
if you imagine gravity as a force vector going through the
crystal in the oscillator, you can imagine a minute
deformation of the crystal as the vector is rotated through 90°.
That deformation gives rise to, as you report, mHz variation in
10?MHz, or parts in 10-10. That's pretty good to be
able to measure.
Full disclosure: I've not done the thinking to check that it
could not be considered a relativistic effect. The effect would be
around 1 in 10-9 for Earth's surface gravity, subject
to finding a credible vectorial mechanism. [Best to check the 10-9.]
We're now in serious physics experimenter territory, allowing for
all the uncertainties and experimental errors in what one is
measuring. Well, Scotty, we can measure it, but what exactly
are we measuring?
73, Stay Safe,
Robin, G8DQX
On 08/01/2023 21:48, Jeff Green wrote:
toggle quoted message
Show quoted text
Friday
afternoon the instrumentation and laboratory supervisor showed
me an aspect of measurement uncertainty I'd never heard of.
She used an
new Keysight 53220A 13 digit
frequency
counter and my "?UTC 108663
MY3109 NOX038663XS 10MHz 10.0MHZ OCXO Double Oven Ultra
Precision oscukkatir:
?
New ultra
precision, high quality UCT 10MHz Double Oven OCXO crystal
oscillator
?
…They trim
to 10.0000000.X MHz and hold it for days at a time in a regular
room with no special temperature control. The room is typical
shirt sleeve environment.
With the
above as background.
?
The lab
supervisor had asked me to bring in an oscillator and we let
it run overnight.
?
We trimmed
the oscillator to read 10.00000000000MHz.
When she
rotated the oscillator it shifted a few milihertz but returned
to exactly
10.00000000000MHz
when placed in the original plane.
?
?
?
?
?
I found an online video which
demonstrates this oddity:
|
Re: NASA: Split Lock Washers Are "Useless"!
To Mikek, I didn't worry about starting a flame war, just didn't want to clutter things up with stuff so far off topic. As the socio-/psycho-paths continuously out themselves such snips of insight are very much on the topic of the very survival of humanity. That said, lists such as this aren't the place but the occasional, well timed kick at those particular cats is useful cause for further consideration.
|
Re: NASA: Split Lock Washers Are "Useless"!
To the group, please do not respond to this post, I will delete it in a day or so.
I don’t know if you can delete your own posts on the forum - I have disabled editing, but I am unsure if deleting is possible. But whilst some people choose not to receive emails from the forum, a lot of people do. You can not delete what’s in their inbox.?
?
Consider it a warning to the evil that is out there just waiting to ambush you.
?
My EE friend talks of her as Miss Psycho of 1974. Charming, witty, beautiful, and dangerous as a cobra shedding it's skin.
?
?
The same day Miss Psycho also loosened the lug nuts on her car wheels.
They got off lucky, Miss Psycho was a competent organic chemist and synthesized a liter of the odor from decaying meat and dosed a the Porsche of a student who ignored her charms.
?
Sociopaths are so dangerous because they are chameleons, able to hide in plain sight.
?
I had never heard of sociopathology until? my friend clued me in and loaned me a copy of The Sociopath Next Door.
?
Normal people don't stand a chance against sociopaths,
?
?
?
Based on personal experience, I'd say being a sociopath is the first requirement to be a venture capitalist, aka vulture capitalist.
?
?
-- Dr. David Kirkby, Kirkby Microwave Ltd, drkirkby@...Telephone 01621-680100./ +44 1621 680100 Registered in England & Wales, company number 08914892. Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, Chelmsford, Essex, CM3 6DT, United Kingdom
|
Re: NASA: Split Lock Washers Are "Useless"!
I don't know why you would delete it, I see some interesting links and tested information.
?I'll copy the whole thread for my chemist son that is doing mostly mechanical now.
?I've read it twice I don't see any flame war.
|
Sam Reaves
Pete_G4GJL
Dr. David Kirkby, Kirkby Microwave Ltd
Bill Perkins