Re: 53181A 3 GHz prescaler from China
I¡¯ve upgraded my 53181 with an eBay prescaler and oven timebase. I believe I got them from a fellow in Poland. No problems at all. For the timebase I calibrated it to a rubidium standard as described in the manual.?
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Re: HP P532A Frequency Meter Manual
On 5/24/22 17:04, johnasolecki@... wrote: I recently acquired an HP P532A frequency meter. I know it's a resonant cavity device that goes from 12.6 GHz to 18 GHz but I don't how or what to hookup to the two flanges to get it to work.
I've seen the Signal Path video but the unit he demos is a different frequency range and has connectors rather than flanges. There are some manuals and app notes on eBay but each is twice what I paid for the device.
I have signal sources and detectors in the correct frequency range, I just need to know how to connect to the flanges. Does anyone have any info? These are "waveguide flanges". Waveguide is a common, very efficient way to move microwave energy around. See the Wikipedia article about it for an introduction. The size of a waveguide, and thus the size of its flanges, depends on the frequency of their intended use. These are (generally) standardized, and have a standardized nomenclature. Your P532A has "WR62" waveguide flanges. If you look for a WR62 waveguide to coax adapter, you should be able to find something that makes sense. For these frequencies you'll likely be working with type N, SMA, APC-7, or 3.5mm connectors. There are waveguide to coaxial cable adapters available, for different sizes of waveguide flanges. This is quite a few orders of magnitude higher in frequency than the audio gear I normally work on... Oh this stuff is great fun. You'd better free up some space and budget, you're gonna need it! ;) -Dave -- Dave McGuire, AK4HZ New Kensington, PA
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HP P532A Frequency Meter Manual
I recently acquired an HP P532A frequency meter. I know it's a resonant cavity device that goes from 12.6 GHz to 18 GHz but I don't how or what to hookup to the two flanges to get it to work.
I've seen the Signal Path video but the unit he demos is a different frequency range and has connectors rather than flanges. There are some manuals and app notes on eBay but each is twice what I paid for the device.
I have signal sources and detectors in the correct frequency range, I just need to know how to connect to the flanges. Does anyone have any info?
This is quite a few orders of magnitude higher in frequency than the audio gear I normally work on...
Thanks, ????????????????
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Re: 53181A 3 GHz prescaler from China
Same thing for me, the option 3GHz (from China) works fine with my 53132A. I¡¯ve done sensitivity test when I bought it, and it was OK. ? Yves ? I bought one a while back for my 53132A. I haven't done much testing of it, but it seems to work just fine.?
Keith
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Re: HP 8662A Power up - overvoltage shutdown
I've done further checking.
The machine is rated for use in the UK at 230V,and the main selector voltage switch is set correctly and the two fuses are rated correctly (2.5A and 0.5A).
I had problems with over voltage. I got UK Power Networks to reduce the voltage. But speaking to their engineers, UK Power Networks aims to supply consumers 245-250 V in rural areas.? They get far more complaints about under voltage than over voltage, and of course, higher voltages means less power wasted by them.?
I always set my equipment for 240 V. My mains voltage is pretty constant 235 +/- 4 V. But I am fairly close to an 11 kV transformer.?
Although the UK is officially 230 V, I don¡¯t think anyone is trying to move us to 230 V.?
Tony
_._,_._,_
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
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Re: first post - new home lab - tips on using HP/Agilent gear
I think these "prefer" a sine wave but will accept either.
toggle quoted message
Show quoted text
On Tue, May 24, 2022 at 11:58 AM, Mark Bielman wrote:
Samudra,
I did this with a KTS-250 (the smaller version, setup as 1 input x 8 outputs) and I changed everything to 50 Ohms... works great. Not sure you need to though.
Have the schematic somewhere in my stash. Not much to it. I think the resistors are in a SIP so I used the DIY method instead of buying some.
I would NOT recommend connecting all the inputs together as that would load the GPSDO too much. If you need more than 8 references, better to:
Feed GPSDO output to KTS input. Use 1 of the 8 KTS outputs and connect to another KTS input. Etc, etc. Then each KTS group will have 7 reference outputs except the last one will have 8.
Follow that?
Have fun!
Mark
Interesting.- thank you Mark. I don't mind DIY, if I had a schematic. I would appreciate a suggestion if we can convert it 50 ohm distribution. That's a resistor network at the end of the signal path or so, per the youtube video tear down I think. But if 75/50
ohm in such a small signal chain is not really critical for distributing 10 MHz, to a short few runs of BNC cable - then all the better. Yes, I did get the tip to use two stages for distribution of the 10 MHz ref clock.?
The GPSDO device is s a Chinese clone of PLL-GPSDO BG7TBL. Just arrived and waiting for it to warm up with the antenna outside my window. The output is noted as "SINE WAVE,6dBm+-2dB", so that's fairly hefty and wondering if this is useful or do we need to attenuate
it for a cleaner signal? I'll hook up an oscilloscope shortly to see the 10 MHz carrier.?
Do HP equipment mind a sine-wave and not a square wave? Haven't read the big manuals yet in detail :-)?
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Re: HP 3465A offset when input shorted
Ok well that was embarrassing. I found out what was wrong with it purely by accident. Looks like CR9 was broken. I was inspecting the area around the high impedance after the 100K carbon comp input resistor and clamp and and noticed that CR9 looked a bit suspicious. I poked the leg with my DMM probe and it fell to pieces. Not sure of the failure mode exactly but now it's out of circuit it works absolutely fine. The original role was half of a voltage clamp which makes sense with respect to the offset measured. I assume it was damaged by over-voltage or was leaking. Picture for reference. The blob of leg is actually dangling from the broken leg by a microscopic metal fibre.?  I checked the input scale was ok by attaching a voltage source to the input terminals and measuring Q16 gate and it was exactly what was expected from the divider arrangement. It appears to zero and work fine now! Now I can't leave it like this as it's the voltage clamp on the input so it'll probably blow up something else without it if it gets overvoltage input. The part is 1901-0586 which appears to be a TO18 canned diode. It's not in the usual parts cross references unfortunately. Vendor is HP, spec is derived from SM as DIODE - GEN PRP 30V 25MA. ?As it's got en expensive package, it smells like it might be a low leakage type, possibly a diode connected BJT or FET. Any thoughts?
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Re: Thoughts on unusual snubber failure mode AC Source HP6813B ?
Hi Mike,
I'm a bit slow on responding....
Great that the manual was what you needed.
Unfortunately I can't help you with the transistors, but hope you are able to source them. Good luck with the repair
Regards, Askild
That's perfect, thanks a heap Askild :-o)
I aided keysight first head office in USA for that but, instead the 'applications' engineer reminded me it was out of service and as it was upgraded to 6813B some years ago from the 6813A including all the extra DSP for harmonic flicker tests etc it was still registered as the A version. Whereas keysight in Australia calibrated it as the B version and added the correct front panel id sticking etc.
Your 3rd edition appears spot on for the A9 output filter, which appears intact though the reverse diode variance on the FETs seems 1% variance when I'd expect lower than 0.5% - not surprising as they are date coded 0425. All gate impedances better than 600 Meg Ohm.
Looking for two sets of IRF 450 TO-204AA devices ie 8 each total 16 or batch of 20, though at least one set plus two spares all same date code would be ok. Infinion (used to be international rectifier) list them as 'Active' and afaik some milspec equipment in USA still use them but, qualified retailers list them as obsolete :-(
I guess I could replace with later irfp devices but, fiddly as heatsink not compatible, though can be worked around. Would need to ensure gate impedances matches so no introduced ringing which could compromise gate breakdown...
It troubles me? though upon close inspection of heatsink minimal if any silicone thermal paste & one side only, cracked TO-3 mica insulators and very odd misalignment of heatsink to PCB such that (only) the air gap between each to-3 devices leads as little as just under a mm. Fortunately though MOSFETs socketed :-)
So will be sleeving the leads & replacing all insulators and new silicone thermal paste as old silicone paste can be compromised via bacteria or fungi - humidity related. Fortunately heatsink floating (no warning sticker on it though), on insulated thermoset blocks so devices not ground referenced to AC coupling of Drain or Source etc. What an interesting set of circumstances, still awaiting feedback from Infineon on equivalent MOSFETs if there's no existing stock. I have been told Infineon occasionally run a batch to restock for the milspec supporting USA military service. The IRF 450 part of their HiRel range and offer a Rad Hard option too and listed as still Active.
Next is to look at all the components which drive the A7 inverter MOSFETs, seems same in 3rd edition as 4th edition. I'm now curious how compatible the later 4th edition A9 output filter (plastic pack MOSFETs) is with the other modules especially A7 inverter from early 2000s A or B versions which used metal can MOSFETs.
If anyone has IRF 450 eg 20 off and can confirm static safe storage and static safe shipping and all same date code or at least 10 each same code then please email or message through here, thanks?
Thanks again for your link spot on, all the best for now, cheers
Regards
Mike Massen
Perth, Western Australia
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Re: HP 3465A offset when input shorted
Ok got a decent DMM at my disposal. Scope due to arrive tomorrow.
I applied the following test cases:
1. From step 5-6. Short V/ohms and COM terminals, set DCV and 10m range. Unstable reading at 0.3-0.4 on the display. ZERO ADJ has no visible function.
2. From step 5-31. Again ZERO ADJ has no visible function.
3. From step 5-36. Shorted Q16 to ground, adjusted R50 to print DCTP in spec to 0.1mV. It was at 93mV which suggests someone was already playing with it :(
Now ZERO ADJ now has 2-3mV swing in either direction but the 10m range it's showing 0.214 still and drifting when inputs shorted and Q16 no longer shorted.
One thing I did try, which I am hoping is not what I think it is, was to check the input impedance of the meter with the 34401A. On the 20,200,2000 ranges it's 10M as expected but on 20m, 200m, 2 ranges it's a suspiciously low 210K.
Any ideas of next steps. The diagnostics at this level are somewhat scarce. I'm slowly tracing out the front end switching now.
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Re: first post - new home lab - tips on using HP/Agilent gear
From the time-nuts side of things, the general consensus is that the mismatch between 50 and 75 ohms at the typical 5 or 10 MHz distribution frequency is a complete non-issue. Even more so when you realize that the reference inputs on a lot of devices aren't very close to 50 ohms, anyway. (I just had to use a 50 ohm feedthrough at the end of a piece of coax to stop ringing from causing bad jitter in a test circuit.)
toggle quoted message
Show quoted text
On 5/24/22 11:15, Samudra wrote: Thank you Michael, yes, I think they are 75-ohm, so ¡ at short distances (in the same rack) what can I do to match the 50-ohm interfaces with the test equipment. I bought this years ago, and didn¡¯t think of what would happen when I connected it ¡
Here are some specs from the GE INTERLOGIX KALATEL KTS-250-16. Am I wrong in assuming that this could be useful, or I should I dump it and source a RF divider/combiner with 50-ohm interfaces and save on the hassle ?
What¡¯s interesting is the ¡°self-termination feature¡± .. mentioned from the brochure:
The KTS-250-16 is a video distribution amplifier that features eight group of input/output channels. Each group can be configured as a single 1x8 video distribution amplifier or two 1x4 video distribution amplifiers. This enables users to set multiple configurations from 8 to 16 inputs by up to 64 outputs. Each output provides unity gain into a 75-ohm load ensuring that the output signal is equal to that of the input. *Unused outputs self terminate*.
Eight input/output groups; each configurable as a 1 x 8 video
distribution amplifier or two 1 x 4 video distribution
amplifiers
l
l Equal video strength for all outputs
l Color compatible
l Unused outputs are self-terminating
l NTSC and PAL compatible
l Only 3.5 inches (2U) of rack space
Electrical
l Input voltage: 12 VAC/15 VDC
l Input power: 0.8 VA
l Video input voltage: 0.5 to 2 V pk-pk
Video
l Inputs: Up to 16
l Outputs: Up to 64
l Impedance: 75 ohm, inputs and outputs
l Bandwidth: 16 MHz
l Signal-to-noise ratio: -75 dB RMS typical
l Crosstalk: -85 dB typical
l Gain (into a 75-ohm load): 0 dB ¡À 0.5 dB typical
l Differential gain: 0.5% typical
l Differential phase: 0.5¡ã typical
Connections
l Power: 2.1 mm x 5.5-mm; center-positive jack
l Video: BNC connectors
Controls
l Mode selector switch
*From:* [email protected] <[email protected]> *On Behalf Of *Michael A. Terrell
*Sent:* Tuesday, May 24, 2022 3:38 AM
*To:* [email protected]
*Subject:* Re: [HP-Agilent-Keysight-equipment] first post - new home lab - tips on using HP/Agilent gear
Are the video amplifiers 50 or 75 ohm?
On Mon, May 23, 2022 at 10:58 PM Samudra <samudra.haque@... <mailto:samudra.haque@...>> wrote:
Hi, I recently cheaply (< $700) acquired working (they power on) set
from a deceased engineer's estate sale in the US:
* HP 8566B 100 Hz - 22 GHz spectrum analyzer (two sections)
* HP 8671B CW Synthesized Generator (2-18 GHz)
I have used HP/Keysight/Agilent systems in labs before, but this
time these are "mine" :-)? I also have a (nicely serviced and
working) HP 5342A Microwave Frequency counter, that should be good
to 18 GHz, and I want to experiment (I am a ham radio operator,
engineer) with RF signals for TX, RX by designing a few PCBs using
microwave semiconductors, FPGA etc.,
I also have coming soon to my home lab a GPS disciplined oscillator,
10 MHz OCXO ref, with a single output,*but from another project I
have a unity-gain 16-bank (1 in, 4 output) BNC video distribution
panel,* which if all sixteen (16) inputs were utilized, would
produce 64 outputs. So, can I ask in general for some assorted
configuration tips please?
1. When the CW Generator is turned on,after warm up, what is the
procedure to check if the power meter (left side) is functional?
the right side does power up with illuminated symbols - and
frequency adjustment can be done manually, but what about the
left side, what should I be seeing to verify functionality -
other than RF produced that can be "seen" in the spectrum
analyzer - I know that unit works.
2. Assuming I want to distribute 10 Mhz clock, ;is distributing the
master clock ref via BNC T-connectors? worse than individual
lines from the unity amplifier bank?
3. Assuming a single 10 MHz clock distributed: how do I verify
"correct operation" of the Spec. An + CW Generator + Frequency
Counter ? What are the go/no-go tests?
4. I want to use automation to record and run tests - and have an
available LINUX workstation in the same rack with PCI-E x1 and
x16 slots available. Any tips on LINUX GPIB etc? Is a GPIB-USB
better than GPIB-Ethernet for accessing multiple machines? Any
horror stories? How is the support in LINUX compared to Windows
10/11 nowadays for GPIB users who don't have NI toolsets yet?
5. is earthing a big deal between the units if they are fed from
the same power distribution unit on a single phase? Thanks for your time. For convenience I have numbered the questions
above. Didn't want to create too many topics on this first day of
joining this group.
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Re: Anyone tried using a CW syntesizer as frequency marker with 8510C?
HP8350B module has DC-FM capability. With an external PLL with correct settings, it can be locked use the AUX YIG signal from the back. However make it work with 8510 require some additional works, a microcontroller need to be insert between 8510 and your source e.g. 8350 + PLL?to make it look like a 8340 or 836x source that support ¡°step¡± sweep.
?
Or you could try other HP CW source, some of them may work under step mode or at least segmented sweep mode.
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Re: HP 8662A Power up - overvoltage shutdown
Yes, current sense resistor is in spec. It¡¯s not the current foldback that is tripping the supply as far as I can tell. It¡¯s an over voltage on the linear supply input to the -40V rail.
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Re: HP 8662A Power up - overvoltage shutdown
Yes, my belief was that UK mains voltage had 220V as the lower side and could go to 240V or more as you say.
I don¡¯t think that is the circuit - I¡¯m referring to the A7A1 PCB circuit with three zener diodes that monitor the three linear supply inputs which are wired-OR and disable the inverter when any one is tripped.
Tony
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Re: HP 8662A Power up - overvoltage shutdown
Hi Tony
In the UK the actual mains voltage is NOT 230VAC, it is frequently nearer to, if not over 250 VAC.
When the UK harmonised with the EU 230VAC ?we did not change our mains voltage, just the acceptable tolerances were widened to make the UK compliant.
?
Just for clarity are we talking about the over voltage circuit that sits across C2 and C3 tripping?
?
G Edmonds
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Re: first post - new home lab - tips on using HP/Agilent gear
On Tue, May 24, 2022 at 11:58 AM, Mark Bielman wrote:
Samudra,
I did this with a KTS-250 (the smaller version, setup as 1 input x 8 outputs) and I changed everything to 50 Ohms... works great. Not sure you need to though.
Have the schematic somewhere in my stash. Not much to it. I think the resistors are in a SIP so I used the DIY method instead of buying some.
I would NOT recommend connecting all the inputs together as that would load the GPSDO too much. If you need more than 8 references, better to:
Feed GPSDO output to KTS input. Use 1 of the 8 KTS outputs and connect to another KTS input. Etc, etc. Then each KTS group will have 7 reference outputs except the last one will have 8.
Follow that?
Have fun!
Mark
Interesting.- thank you Mark. I don't mind DIY, if I had a schematic. I would appreciate a suggestion if we can convert it 50 ohm distribution. That's a resistor network at the end of the signal path or so, per the youtube video tear down I think. But if 75/50 ohm in such a small signal chain is not really critical for distributing 10 MHz, to a short few runs of BNC cable - then all the better. Yes, I did get the tip to use two stages for distribution of the 10 MHz ref clock.? The GPSDO device is s a Chinese clone of PLL-GPSDO BG7TBL. Just arrived and waiting for it to warm up with the antenna outside my window. The output is noted as "SINE WAVE,6dBm+-2dB", so that's fairly hefty and wondering if this is useful or do we need to attenuate it for a cleaner signal? I'll hook up an oscilloscope shortly to see the 10 MHz carrier.? Do HP equipment mind a sine-wave and not a square wave? Haven't read the big manuals yet in detail :-)?
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Re: first post - new home lab - tips on using HP/Agilent gear
On Tue, May 24, 2022 at 03:37 AM, Michael A. Terrell wrote:
Are the video amplifiers 50 or 75 ohm?
?
I found a very hiqh quality detailed breakdown video on YouTube.about GE Interlogix? Kalatel?KTS-250-16 (my unit)? ??by W2AEW (2015)
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Re: first post - new home lab - tips on using HP/Agilent gear
Samudra,
I did this with a KTS-250 (the smaller version, setup as 1 input x 8 outputs) and I changed everything to 50 Ohms... works great. Not sure you need to though.
Have the schematic somewhere in my stash. Not much to it. I think the resistors are in a SIP so I used the DIY method instead of buying some.
I would NOT recommend connecting all the inputs together as that would load the GPSDO too much. If you need more than 8 references, better to:
Feed GPSDO output to KTS input. Use 1 of the 8 KTS outputs and connect to another KTS input. Etc, etc. Then each KTS group will have 7 reference outputs except the last one will have 8.
Follow that?
Have fun!
Mark
|
Re: HP 8662A Power up - overvoltage shutdown
I've done further checking.
The machine is rated for use in the UK at 230V,and the main selector voltage switch is set correctly and the two fuses are rated correctly (2.5A and 0.5A).
I checked the +20V, -10V and -40V regulated outputs using a triggered scope and they seem to all ok although some to not reach final voltage before the PSU cuts off.
I have checked the *inputs* to the three regulators and found the following:
TP4 +20V? Input spec = 23V +/- 2.3V? ?Actual = +21.66V (in spec)
TP5 -10V Input spec = -13V +/- 1.3V? Actual = -12.2V (in spec)
TP6 -40V Input spec = -45V +/- 4.5V Actual = -55.2V @220V and -56.3V @ 230V (not in spec)
So it seem likely that VR2 (57.5V zener) is tripping the over voltage circuit.
I can't see why one rail would be out of spec if the others are ok. There is not much between that and the rectifiers from the main inverter. I have checked the smoothing cap C11 and replaced it (although it tested fine). If R11 has drifted higher than 110k, could that make so much difference?
thanks for all suggestions - the help on this group is great.
Tony
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Re: first post - new home lab - tips on using HP/Agilent gear
Thanks for the precise instructions - I will do that this coming weekend after another session of home renovations in the new place is complete. I'm bookmarking this.?
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Re: first post - new home lab - tips on using HP/Agilent gear
Thank you Michael, yes, I think they are 75-ohm, so ¡ at short distances (in the same rack) what can I do to match the 50-ohm interfaces with the test equipment. I bought this years ago, and didn¡¯t think of what would happen when I connected it ¡ ? Here are some specs from the GE INTERLOGIX KALATEL KTS-250-16. Am I wrong in assuming that this could be useful, or I should I dump it and source a RF divider/combiner with 50-ohm interfaces and save on the hassle ? ? ? What¡¯s interesting is the ¡°self-termination feature¡± .. mentioned from the brochure: ? The KTS-250-16 is a video distribution amplifier that features eight group of input/output channels. Each group can be configured as a single 1x8 video distribution amplifier or two 1x4 video distribution amplifiers. This enables users to set multiple configurations from 8 to 16 inputs by up to 64 outputs. Each output provides unity gain into a 75-ohm load ensuring that the output signal is equal to that of the input. Unused outputs self terminate. ? Eight input/output groups; each configurable as a 1 x 8 video distribution amplifier or two 1 x 4 video distribution amplifiers l l Equal video strength for all outputs l Color compatible l Unused outputs are self-terminating l NTSC and PAL compatible l Only 3.5 inches (2U) of rack space ? Electrical l Input voltage: 12 VAC/15 VDC l Input power: 0.8 VA l Video input voltage: 0.5 to 2 V pk-pk Video l Inputs: Up to 16 l Outputs: Up to 64 l Impedance: 75 ohm, inputs and outputs l Bandwidth: 16 MHz l Signal-to-noise ratio: -75 dB RMS typical l Crosstalk: -85 dB typical l Gain (into a 75-ohm load): 0 dB ¡À 0.5 dB typical l Differential gain: 0.5% typical l Differential phase: 0.5¡ã typical Connections l Power: 2.1 mm x 5.5-mm; center-positive jack l Video: BNC connectors Controls l Mode selector switch ? ? ?
toggle quoted message
Show quoted text
From: [email protected] < [email protected]> On Behalf Of Michael A. Terrell Sent: Tuesday, May 24, 2022 3:38 AM To: [email protected]Subject: Re: [HP-Agilent-Keysight-equipment] first post - new home lab - tips on using HP/Agilent gear ? Are the video amplifiers 50 or 75 ohm? ? Hi, I recently cheaply (< $700) acquired working (they power on) set from a deceased engineer's estate sale in the US: - HP 8566B 100 Hz - 22 GHz spectrum analyzer (two sections)?
- HP 8671B CW Synthesized Generator (2-18 GHz)
I have used HP/Keysight/Agilent systems in labs before, but this time these are "mine" :-)? I also have a (nicely serviced and working) HP 5342A Microwave Frequency counter, that should be good to 18 GHz, and I want to experiment (I am a ham radio operator, engineer) with RF signals for TX, RX by designing a few PCBs using microwave semiconductors, FPGA etc.,?
I also have coming soon to my home lab a GPS disciplined oscillator, 10 MHz OCXO ref, with a single output, but from another project I have a unity-gain 16-bank (1 in, 4 output) BNC video distribution panel, which if all sixteen (16) inputs were utilized, would produce 64 outputs. So, can I ask in general for some assorted configuration tips please? - When the CW Generator is turned on,after warm up, what is the procedure to check if the power meter (left side) is functional? the right side does power up with illuminated symbols - and frequency adjustment can be done manually, but what about the left side, what should I be seeing to verify functionality - other than RF produced that can be "seen" in the spectrum analyzer - I know that unit works.?
- Assuming I want to distribute 10 Mhz clock, ;is distributing the master clock ref via BNC T-connectors? worse than individual lines from the unity amplifier bank??
- Assuming a single 10 MHz clock distributed: how do I verify "correct operation" of the Spec. An + CW Generator + Frequency Counter ? What are the go/no-go tests??
- I want to use automation to record and run tests - and have an available LINUX workstation in the same rack with PCI-E x1 and x16 slots available. Any tips on LINUX GPIB etc? Is a GPIB-USB better than GPIB-Ethernet for accessing multiple machines? Any horror stories? How is the support in LINUX compared to Windows 10/11 nowadays for GPIB users who don't have NI toolsets yet?
- is earthing a big deal between the units if they are fed from the same power distribution unit on a single phase??
Thanks for your time. For convenience I have numbered the questions above. Didn't want to create too many topics on this first day of joining this group.?
|
Dave McGuire
Dr. David Kirkby, Kirkby Microwave Ltd