Date   

Re: GATs

Julian, G3YGF
 

Chris,
Yes, I think it was 1979. We used a GAT5 to get a 0.5dB preamp for G3OUR's 432 EME system, measured with the aid of liquid N2. If I remember correctly, the input circuit was about 3" of 1" wide copper foil stripline... It was written up in the Dec 80 Radcom.
About that time, we also obtained a ceramic substrate and chip with about 12dB gain on 10GHz to help us listen for G3JVL from GM land - all supplied courtesy of the same Dr Cripps/G3WDG/Plessey - again, many thanks!...
We rapidly learned a lot about LNAs, GaAsFETs, and the importance of making up reliable cables and T/R sequencing systems...
I think G3WDG wrote up a 1.3GHz version of the GaAsFET in Radcom shortly after.

I also recall a visit to G3LTF around that time, and his comment on our 432 GaAsFET was something like - "Ok, but you had it easy - I was getting similar results from a paramp, with a varactor pump at 10GHz, some time ago!".

<end of reminiscences>!

Julian, G3YGF

On 09/06/2021 20:40, Chris Bartram G4DGU wrote:
Hello Paul,

I did use a GAT3 and GAT5 at one time
I can't resist a comment on that ... So did I! I seem to remember using a GAT2 and GAT3 and maybe a GAT5. They taught me a lot about the need to get good T/R switching isolation, and to use proper sequencing for the c/o process :-)
.
My source was a certain Dr.(now Prof.) Cripps (ex-G3TPF) via Charlie, G3WDG. In about 1979 mine were used in a preamplifier for 432MHz EME, and very much from memory I achieved a noise figure of around 0.7dB measured by a thermal hot/cold source. that was more than 0.5dB better than I'd achieved with a then state of the art bipolar transistor. With my then 8 yagi antenna and about 700W from a K2RIW amplifier I could hear my own echoes most of the time. I also worked most of the stations then active on the band on CW, although Faraday wouldn't cooperate for a few. I think I was the first UK station to use a GaAsFET preamplifier for EME, beating the G3OUR group at Oxford by a couple of weeks.

Another preamp made from a GAT device was also used in the preamp of the system I used to demonstrate, at about the same time, the possibility of using space debris as a passive reflector by scattering my SSB off a Russian COSMOS launcher in a decaying orbit. That was received by SM6CKU, near Gothenburg, at about 1600km. That wouldn't have been possible without the computing assistance of John Morris G4ANB. We seem to have achieved a World first, and felt we were creeping towards a completed QSO. However, those tests came to an abrupt end when our source of ephemeris data was pulled by a research establishment at Slough ...

73

Chris G4DGU

PS. Apologies to anyone reading this who has seen me comment on these tests before. I remain very proud of what we did at that time, and it is in the nature of the hobby for tests like those to become forgotten.







Re: LA2T9Q ''6GHz' amplifier spec?

Iain Crawford
 

Nice. 400 watt TWTA. 8-18GHz. There's 2 of them (lots 84 & 85). I wonder if they work?
I'd put in a bid but collecting it might be a problem. :-)
https://www.etm-inc.com/std-power.html

73 Iain VK5ZD


Re: N plug solder for semi rigid

Wilko
 


Re: GATs

Andy G4JNT
 

The red spot and black spot FETs used in the G3WDG 10Ghz transverter from the 1990s were Plessey discards.
Presumably what the GATs morphed into after several years of R+D




On Wed, 9 Jun 2021 at 21:53, Clive Elliott GW4MBS via groups.io <humber1ton=btinternet.com@groups.io> wrote:
I still have this which I think is a GAT3, given to me 40+ years ago by either G3YGF or G3JVL. At the time I was living in Hampshire directly under their tropo path & gave me good experience in looking for weak signals. In fact I have to thank Julian for the nudge to take up CW to make full use of weak signals, hence my change in callsign.
--
Clive GW4MBS (ex-G8ADP)
Pottering on 6m - 3cm in a valley in IO71XW where any QSO is a triumph of optimism over geography!


Re: GATs

Clive Elliott GW4MBS
 

I still have this which I think is a GAT3, given to me 40+ years ago by either G3YGF or G3JVL. At the time I was living in Hampshire directly under their tropo path & gave me good experience in looking for weak signals. In fact I have to thank Julian for the nudge to take up CW to make full use of weak signals, hence my change in callsign.
--
Clive GW4MBS (ex-G8ADP)
Pottering on 6m - 3cm in a valley in IO71XW where any QSO is a triumph of optimism over geography!


Re: Unused Unloved K2RIW Amp

Frank, G0GSR
 

Isn't the combined AM/PM noise so bad from the 9700 that it would be antisocial to run a high power amp, especially in the UK where its hard to get any distance away from anyone?
Frank


Re: Unused Unloved K2RIW Amp

Andy Rutter, G8HCK
 


I have a complete kit purchased a LONG time ago, back when I was overly enthusiastic! I have excavated it from the store room and taken some photos

    https://www.dropbox.com/sh/d1s9o6uoegj20gz/AABJOhsV2lr7xpgFAd6SYXmha?dl=0

It is in good unused condition, a bit tarnished due to the 30 odd years storage, but I am sure that will clean up. The kit comprises metalwork, sockets, PTFE, EHT connectors and cable. I have honestly no idea what it is worth so, if you want it, make me a reasonable offer (andy <at> acronym.co.uk).

I also have the EHT transformer which I will photo tomorrow if there is any interest.

--
    Andy, g8hck


On 09/06/2021 18:00, Derek Brown G8ECI via groups.io wrote:
Anyone have a unused K2RIW 432 Amp built or partially or even just the chassis, I have the Sk630 bases, being a serious long time user of the 4CX250B, I need a few more watts than what my IC9700 puts out as as evident during last night UKAC on 70cm heard loads of stations, but they not hearing moi !!   Also as I qsying from JO03 to IO93, will no longer have that tempting Locator to lure in the stations. So if you have one lurking in that shed, under the bench or about to be scrapped.

Please email me,
 
73 Derek G8ECI


GATs

Chris Bartram G4DGU
 

Hello Paul,

I did use a GAT3 and GAT5 at one time
I can't resist a comment on that ... So did I! I seem to remember using a GAT2 and GAT3 and maybe a GAT5. They taught me a lot about the need to get good T/R switching isolation, and to use proper sequencing for the c/o process :-)

My source was a certain Dr.(now Prof.) Cripps (ex-G3TPF) via Charlie, G3WDG. In about 1979 mine were used in a preamplifier for 432MHz EME, and very much from memory I achieved a noise figure of around 0.7dB measured by a thermal hot/cold source. that was more than 0.5dB better than I'd achieved with a then state of the art bipolar transistor. With my then 8 yagi antenna and about 700W from a K2RIW amplifier I could hear my own echoes most of the time. I also worked most of the stations then active on the band on CW, although Faraday wouldn't cooperate for a few. I think I was the first UK station to use a GaAsFET preamplifier for EME, beating the G3OUR group at Oxford by a couple of weeks.

Another preamp made from a GAT device was also used in the preamp of the system I used to demonstrate, at about the same time, the possibility of using space debris as a passive reflector by scattering my SSB off a Russian COSMOS launcher in a decaying orbit. That was received by SM6CKU, near Gothenburg, at about 1600km. That wouldn't have been possible without the computing assistance of John Morris G4ANB. We seem to have achieved a World first, and felt we were creeping towards a completed QSO. However, those tests came to an abrupt end when our source of ephemeris data was pulled by a research establishment at Slough ...

73

Chris G4DGU

PS. Apologies to anyone reading this who has seen me comment on these tests before. I remain very proud of what we did at that time, and it is in the nature of the hobby for tests like those to become forgotten.


Re: SMA Adaptors

Gareth G4XAT
 

Thanks Neil, great insight into what I'm trying to do. Made something that 'works' but with just SDR to look at the LNB output, its not exactly precise. Does behave as I expected though, so progress of a sort....
Best wishes
Gareth


Re: Unused Unloved K2RIW Amp

ian hope (2E0IJH)
 

G8DOH had a chassis as I was looking for one as had a damaged one, but I then got gifted our clubs units as our Club chair became serious ill 
 
Ian
M5IJH

 
 
Sent: Wednesday, June 09, 2021 at 6:00 PM
From: "Derek Brown G8ECI via groups.io" <g8eci@...>
To: UKMicrowaves@groups.io
Subject: [UKMicrowaves] Unused Unloved K2RIW Amp
Anyone have a unused K2RIW 432 Amp built or partially or even just the chassis, I have the Sk630 bases, being a serious long time user of the 4CX250B, I need a few more watts than what my IC9700 puts out as as evident during last night UKAC on 70cm heard loads of stations, but they not hearing moi !!   Also as I qsying from JO03 to IO93, will no longer have that tempting Locator to lure in the stations. So if you have one lurking in that shed, under the bench or about to be scrapped.

Please email me,
 
73 Derek G8ECI


Re: Gunns

Paul Evans W4/VP9KF
 

VERY interesting... especially as Solfan used their own mechanical assembly, but we (Plessey) supplied all their Gunn devices! I never did know why they were the few 'device only' buyers, but it had to come down to price. The target for most of those types of units was barely >$10. The device package for the Gunn cost about GBP2.00 and making the device itself was about the same. That doesn't leave much change to make the assembly and test. I seem to remember the target spec was 10 mW. I think they went out in volumes of up to 5,000 per month at times. Our test was a very quick drop in a test rig, check power out and on to the next. I can only assume that the devices were acting as parametric pumps against each other, in the same way a parametric pump amplifier can be made. Of course, this is all a bit mute now because the use of Gunns has been superceded by FET oscillators. By the time we closed, the first volume DBS LOs were being made in-house using DROs [in fact I was in the last skeleton team of 8 people fulfilling an order for such FETs over a period of 5 months].

--
73, Paul Evans G4BKI [VP9KF]


Re: N plug solder for semi rigid

 

On Wed, 9 Jun 2021 at 19:07, Keith Le Boutillier via groups.io <gu6efb=cwgsy.net@groups.io> wrote:

Hi Paul & Alwyn

 

Finding a reliable source of good quality connectors no matter the price is not easy these days.

 

73 Keith D. Le Boutillier GU6EFB


For adapters, I expect Keysight would supply something good if you did not worry about the price. I would expect somewhere in the range of 1000-5000 GBP (sorry, no pound sign on this US keyboard which I must replace).

Dave, G8WRB.


Re: N plug solder for semi rigid

 

On Wed, 9 Jun 2021 at 08:51, alwyn.seeds1 <a.seeds@...> wrote:
Dear Ben,

This is now a bit of a challenge.

Yes, my thoughts too. I was once looking for female-female in N, and tested every one I could get my hands on. The results were surprising.

H&S had the worst RF performance, but the threads are very well formed. They were made in China. I was just about to phone H&S until I realised that it actually met the specification.

A cheap Chinese one that someone sent me for free had the best RF performance. However, the threads looked like they had been cut with an axe.

The Telegartner, J01024A0004, available from RS

was the best I found in terms of a compromise between RF performance and the quality of the threads. 


There are many distributors of N connectors who are selling parts with poor design/poor tolerances- I have measured these and they show worse return loss than what used to be available.

Huber and Suhner are good, also Telegartner as a lower cost option, if they meet your spec.
 
I guess it depends on the exact connector, but for what I wanted, f-f thru, the H&S had a poor specification, which it did meet.

So, I think you now have to check spec. very carefully, and do n’t be surprised if a connector that meets the MIL spec. to 12 GHz or 18 GHz is quite pricey.
 
So far as I know, there is no longer any manufacture of N connectors in the UK.

There seems very little RF engineering in the UK compared to Germany or the USA, even when taking the different populations into account. 

Regards,

Alwyn G8DOH
 
Dave, G8WRB


Re: Gunns

 

On Wed, 9 Jun 2021 at 13:16, Paul Evans W4/VP9KF <paul@...> wrote:
Well, I was the 2T [two terminal] Device Manager at Plessey Microwave, so I should be able to help you :-) My coverage was from wafer selection and test, epitaxy for all the devices we made, cleanroom design and monitoring, process control and modification, chip and wire bonding, packaging, test and installation into product. I also covered varactors, detectors, IMPATTs and TRAPATTs.

First,  Gunns are not diodes, but they became known as that pretty universally by mistake in the 60s. Secondly, they only display negative resistance above a certain voltage where RF also starts to be generated under the right conditions. Despite extremely tight measurement and QA I used to say 'every single device we make is different'. I never saw any attempt at combining the output of two devices and I would give it zero chance of working (even if only for a very short time under just the right conditions - mostly thermal). I know of several systems where we would dearly have liked to combine devices outputs for more power!
--
73, Paul Evans G4BKI [VP9KF]

Combining two Gunn diodes to get increased power was definitely published in an amateur journal, but I don't know which. I did not dream it, so it has been done. I would expect there to be injection locking, so they are both on the same frequency.

The guy from Virginia diodes was not at all surprised by this. Virginia Diodes make Gunn diodes at over 1 THz.

I recall giving a talk at our radio club on the diodes once. I had a power supply with an ammeter, and people could see the current rise as the voltage was increased. Then when the current started falling, everyone was perplexed. Negative resistance, or more precisely negative dynamic resistance, is not something most people are aware of.

Dave


Re: N plug solder for semi rigid

Keith Le Boutillier
 

Hi Paul & Alwyn

 

All points are very valid and noted, I have used Coax-connectors both myself and at work and have found them to be very helpful. The connectors we have used have been tested and met the specs that were required and worked without issue for us.

I realises that there is much more to connectors than first thought but as the question was asked I thought I would mention their name as a possible source, but it is up to each person to decide if the connector in question is suitable for their requirement.

Finding a reliable source of good quality connectors no matter the price is not easy these days.

 

73 Keith D. Le Boutillier GU6EFB

 

From: UKMicrowaves@groups.io <UKMicrowaves@groups.io> On Behalf Of alwyn.seeds1
Sent: 09 June 2021 14:22
To: UK Microwaves groups.io <UKMicrowaves@groups.io>
Subject: Re: [UKMicrowaves] N plug solder for semi rigid

 

Dear Keith,

 

Coax-connectors are indeed UK based. I do not know where the connectors they sell are manufactured.

 

I note that performance data for the connectors they sell is not on their web-site, but has to be requested.

 

I have tested a few samples of their N connectors. I measured the return loss to be higher than for equivalent connectors made by Radiall, which are, of course more expensive.

 

A coaxial connector requires precision mechanical engineering and stringent materials selection- these do not come cheap.

 

When the applications for these connectors were primarily military, MIL-spec. connectors were commonly available and purchasing was straight-forward.

 

Those days are gone, so care is required, particularly for use above 1 GHz.

 

Regards,

 

Alwyn

 

_____________________________________________________

Alwyn Seeds, Director
114 Beaufort Street (Management) Company Ltd.,
114 Beaufort Street,
London,
SW3 6BU

114 Beaufort Street (Management) Company Ltd., Registered in England and Wales: No. 02797775 Registered Office Address: 114 Beaufort Street, London, SW3 6BU

______________________________________________________

 


Re: Gunns

Graham G3VKV
 

Hi all,
Back in the 80's I used two Solfan iris coupled Gunn oscillators across a magic T to produce more than twice
the output of one unit for wideband FM - a 9mW and 11mW produced 30mW when locked up 
I took the assembly to Crawley Court Round table meeting where it was tested to confirm the results,
The late Tim G3KEU also made one and reported it in the Oct/Nov 1988 Microwave newsletter.
I used mine portable for a number of years. (still got it somewhere)
see
Bob Atkins - KA1GT
                                          Graham G3VKV


Re: Gunns

 

On Wed, 9 Jun 2021 at 10:41, Chris Bartram G4DGU <chris@...> wrote:
Hello Dave,

Being negative resistance devices, Gunn oscillator cavity design isn't
necessarily intuitive, and putting two into a cavity will probably lead
to unexpected results! The guy from Virginia Diodes was probably correct ...

Chris

G4DGU
 
Yes, I think so too. The guy from Virginia Diodes did not even have to think about it - his answer was immediate. He was not in the least bit surprised.

In contrast, the academic from Scotland who said it was rubbish, was not considering the fact that the DC drive to the diodes was far more than the RF output power.


Unused Unloved K2RIW Amp

Derek Brown G8ECI
 

Anyone have a unused K2RIW 432 Amp built or partially or even just the chassis, I have the Sk630 bases, being a serious long time user of the 4CX250B, I need a few more watts than what my IC9700 puts out as as evident during last night UKAC on 70cm heard loads of stations, but they not hearing moi !!   Also as I qsying from JO03 to IO93, will no longer have that tempting Locator to lure in the stations. So if you have one lurking in that shed, under the bench or about to be scrapped.

Please email me,
 
73 Derek G8ECI


Can someone design me an S-Band microstrip filter

Andy G4JNT
 

I don't have much in they way of microstrip design software, and the learning curve is too long to start playing  - especially at this time of year, so:

Is there anyone so au-fait with a microwave / microstrip design package that this spec for a comb line bandpass filter is plug-N-play?   I'm after a 1:1 PCB artwork in some common graphics format like PDF that can just be dropped onto acetate to etch.    Don't mind playing with scalpels and bits of copper foil to do the fine tuning on the fingers, but need to be pretty much there straightaway with finger spacing

Passband to cover 2290 - 2460MHz or even a bit wider, ripple  <0.5dB
Fourth or  higher - not concerned how high it has to go.
Rejection at 2306 >40dB (highest LO)    and > 70dB at 2162MHz (highest image)
Loss isn't terribly important as it'll be for interstage use.

PCB material 0.8mm  Er 2.50   copper thickness 35um
Think it's RT-Duroid, I do have a fair bit of that PCB material in the junk box and it's about time it was used for something useful. 
Measured the Er and it does come out close to 2.50
 
I reckon  you can guess the application.   It's the only uWave band I don't have a 144MHz drive transverter for, so might as well make it cover the full allocation in one go.

TIA 


Re: Gunns

Paul Evans W4/VP9KF
 

Sorry, before my time - graduated in 1979. Strangely Southampton was on my 'list of 5' when applying, but never went for an interview, never mind a talk.

The person who gave you the talk would have been from Caswell Research and could have been Fred Myers (tall, dark haired guy) or Jim Turner (short, orange-ish hair and beard). They were in on making the worlds first MMICs, before USA, etc. It could have been someone else, they were very heavy into GaAs and epitaxy [vapour phase and later MOCVD].

I did use a GAT3 and GAT5 at one time - they were as rare as hens teeth! If their yield was anything like the normal Caswell yield then that's why they were rare :-(

Most Malvern things didn't end well. So the multi Gunn thing was probably abandoned and done an easier way. All I do know is that they didn't exactly have repeatability on their side. The most notable being the long held rumour that one day they made a 'magic' wafer which produced some Gunns that were twice+ as efficient as any recorded before or since [and exceeded theoretical power yield too]. We never saw anything like that in production, or we would have chased it HARD.

By the way, I did noise test measurements on our devices vs. the competition (Alpha, M/A, etc.) and confirmed what our customers were saying when ordering. We were waaaaay ahead on phase noise and stability. It was down to our epitaxy and not our fab (as I later proved). In the 80s all of the temporary traffic light heads were coming from us, radar speed meters (Escort, etc.) as well as buckets full of supermarket door openers! Of course, the military side was a little harder to yield. What few would know is that every wafer was run down the line to full mil. spec. until being dropped in superiority at test to 'commercial use'.
--
73, Paul Evans G4BKI [VP9KF]

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