All the places for the 13th Scottish Microwave Round Table (GMRT) were fully booked ahead of the event, which took place on Saturday the 1st of November. The gathering followed its usual successful format, taking place in the Museum of Communication (MOC) in Burntisland in Fife, with doors opening at 09:30. Greeting us at the door and giving everyone a warm welcome was the familiar face of Peter Dick GM4DTH who was keeping the register of attendees and taking payments for the event and the evening dinner.
Attendees took refreshments in the conference room on arrival and immediately started making conversation and renewing acquaintances, whilst others headed for the display area to look through the stalls containing microwave equipment, test gear, and components that were for sale. The test and measurement facility run by Brian Flynn GM8BJF and David Stockton GM4ZNX was already in operation (and was open for business throughout the day during breaks in the presentations).
Museum volunteers were working in the “back room” behind the display area cataloguing their stock during the morning and happily gave a tour of its contents to those who were interested or hadn’t seen their collection before. Seeing old 19 sets and BC221M frequency meters took many of us back to the start of our interest in amateur radio.
The formal event opened at 10:30 AM and Professor Tom Stevenson from the MOC gave the customary welcome to the venue, including domestic arrangements and safety announcement. Martin Hall GM8IEM then welcomed the participants and acted as chair for the morning session. He announced that he had stepped down as the Scottish Regional Representative on the UK Microwave Group Committee in September, and that Peter Bates GM4BYF had agreed to take his place in that role.
The first speaker was Brian Howie GM4DIJ whose talk was entitled “Design and Construction of Feed Horns for the Sky Mini Dish”. Old Sky dishes are readily available at no cost, and Brian first described their characteristics, drawing attention to their elliptical shape. He then went on to describe how to optimise the design of elliptical feed horns for the 3, 6, 9, and 13cm bands for these dishes, including limitations on their performance. Brian showed how to approach the practicalities of constructing the horns, first by making a thin cardboard template and checking that it would fit mechanically, which was then used to cut tinplate (for example from old cooking oil cans) for the final construction. He then went on to present the results of testing which showed them to perform well. The talk resulted in a lively question and answer session!
Following Brian’s presentation there was a short break before Barry Lewis G4SJH (RSGB Microwave Manager) started his talk “Microwave Bands in the Spotlight”. Barry started by explaining his background experience and role in acting on behalf of amateurs, working to defend our allocated spectrum against incursion by commercial interests, which can be particularly difficult where we are designated Secondary Users. Loss of spectrum on the 13cm and 23cm bands has been of great concern to amateurs, and Barry gave the latest updates and potential outcomes to the ongoing negotiations. There is some optimism that in the UK we will be able to retain at least some parts of these bands with meaningful power levels, although our continental neighbours may not be so fortunate, which will restrict DX opportunities. Barry also outlined the potential threats in the higher bands and what the effect might be on our operation. A copy of his Powerpoint presentation illustrating the details will be made available via the GMRT website.
After Barry had answered questions from the floor, we vacated the conference room so that lunch could be set out by the MOC volunteers. We re-assembled in the museum where the entries for the GM4LBV Projects Trophy were displayed for examination by the judges Sam Jewell G4DDK and David Stockton GM4ZNX. When the call went out that lunch was now ready everyone returned to the conference room to enjoy the fine food on offer, and to continue chatting.
Andy Sinclair GM4LLD (ex-MM0FMF), President of the Lothians Radio Society, took over as chair for the afternoon session and introduced Geoffrey Pike GI0GDP as the next speaker. In his talk entitled “PAs – 23cm to 3cm”, Geoffrey shed light on the understanding of “s” parameters used to characterise semiconductor devices, and how to transfer these to a Smith Chart to simplify the design of power amplifiers. He showed how matching circuits could be designed simply, by using the Smith Chart, and recommended the ARRL UHF/Microwave Experimenter’s Manual as a reference guide. He then went on to address some of the practicalities of mounting high power semiconductor devices in these bands and showed some examples of construction. However, he acknowledged that obtaining suitable devices wasn’t easy.
There was another short break before the next presentation, on “3D Printing”, by Mark Hughes GM4ISM, based on his own journey from the research into which printer would be suitable for his requirements, through to the printing of usable components. His motivation was to manufacture parts that couldn’t be bought or were no longer available, and he passed several examples round the room, including element mounts for 23cm Tonna antennas and inserts for connectors. However, he emphasised that there is lots to learn, he had to put in a lot of effort, and that there was a steep learning curve. The range of topics included ensuring the printer you purchase meets your requirements, type of print material, material properties, filament types, design aspects of what is to be printed, how material is laid down, layer adhesion, print orientation and strength, dimensional accuracies, and the associated practicalities.
Immediately following David’s talk, we had the conclusion of the construction competition and award of the coveted GM4LBV Projects Trophy. There were 4 entries this year:
- PCB for PLL Code Loader using RP2040 Zero (Mark Hughes GM4ISM)
- 24 GHz Waveguide switch (Mark Hughes GM4ISM)
- GaAs Amplifier PSU (Mark Hughes GM4ISM)
- Noise figure meter (Brian Flynn GM8BJF)
The judges Sam Jewell G4DDK and David Stockton GM4ZNX described the judging criteria – does it help microwavers, is it innovative, level of documentation etc? They gave a review of each entry, pointing out their respective merits and achievements. All the scores were close, making it a difficult choice – after some deliberation the 24 GHz waveguide switch was declared the winner, and Mark Hughes GM4ISM was duly presented with the trophy. Sam and David thanked Paul Nickalls G8AQA for invigilating their scoring.
Andy Sinclair then provided the closing remarks, thanking the museum volunteers for keeping us well supplied with tea, coffee, biscuits, and scones throughout the day, as well as providing the splendid buffet lunch, and they were given gifts in appreciation to a round of applause from the audience. To further applause, Andy also thanked the organising committee, and in particular Colin Wright GM4HWO who had put together the programme.
Twenty-one attendees (including some spouses and partners) moved on to the Kingswood Hotel in the evening for further socialising and an excellent meal. An auction of items was undertaken, and thanks go to those who made the donations. The proceeds from the auction, other donations, and a small surplus from the door takings are donated to the MOC to support their activities. Further discussions continued until late!
Thanks go to the organising committee of Roger Blackwell GM4PMK, John Cooke GM8OTI, Brian Flynn GM8BJF, David Stockton GM4ZNX, Colin Wright GM4HWO, Ian White GM3SEK, Peter Dick GM4DTH, Andy Sinclair MM0FMF, James Gentles GM4WZP, Colin Murray GM4EAU, Peter Bates GM4BYF, and Brian Howie GM4DIJ.
Post meeting notes:
- We gave a donation of £148 (our excess funds) to the MOC.
- Feedback on the event, ideas for future talks, and any offers of future talks is requested. Please send to Colin GM4HWO by email – his address is available on qrz.com.
- Powerpoint files of some of the presentations will be available via the GMRT website.
Prepared by Martin Hall GM8IEM, with contributions from the organising team.
16-Nov-25 Final V1.3