As a follow up to last week’s presentation, Graham started with a short refresher of what to consider when planning an antenna. By using Sim Smith he demonstrated how to choose correct inputs and the results of those choices. He showed that power could be lost due to the wrong choice and correct matching provided the best power transfer from the rig to the aerial at the chosen frequency for that particular aerial. These results can be seen in real time using Sim Smith which would be rather laborious to calculate using a paper Smith Chart.

To further curtail losses, Graham suggested materials suitable for aerial wire and also inductor construction. He pointed out that lots of gain can be ‘found’ if you know where the losses are!

Graham began by stating that with small aerials you can’t have all the most desired features regardless of what the advertisements say. He defined what a ‘small antenna’ would be with regards to your available garden. i.e. any antenna too small to be resonant at the desired frequency, a dipole less than a half wavelength, a loop less than one wavelength in circumference, a vertical less than a quarter wavelength in height. However, a small aerial can be effective with careful design.  Graham spelled out what we should design for, such as being able to radiate as much RF as possible and to hear weak stations especially on Top Band.

A number of different matching networks were considered and Graham showed the pitfalls of some and the advantages of others.  At this point, he introduced the software programme Sim Smith which can introduce various circuit arrangement for best matching and display the results. Some looked like the most used methods of matching but the programme showed heavy losses in their use. The programme showed the advantage and disadvantage of some baluns and ATUs and where they were best placed.

More discussions followed the use of Sim Smith and how the active Smith Chart could actually make design much easier and faster.  At this point, we ran out of time but Graham said he was willing to come again next week to explain more about the matching conundrum.

Paul began by handing out copies of an article showing how to repurpose Toko inductors to be read while he continued with his presentation. He then said there was a number on the reverse and that was every ones free raffle number. During other explanations about the equipment on display, he would call out a number and award the holder an item from the table. There were several meters, an early Icom TV tuner, a tin of biscuits (un opened) and two tins of Quality Street, also still sealed.

Paul stated he is a ‘valve man, twenty years out of date’.  He then compared some of his large sized test equipment on display and passed around the equivalent modern item which would fit in the palm of his hand. He recounted his work at Henlow, ICL and Stevenage stating that many of the sites have been closed or sold off and the highly qualified workers dispersed.

On his laptop, Paul showed Circuit Wizard, a programme which can be tried for free but a payment is required for the full working version. He explained the usefulness of being able to try a circuit before building it.  Pointing to a very clean looking radio from the 60’s he said the man at the market said he would have to pay a fortune to get it working. But Paul bought it anyway saying it would be worth the time he would spend checking it and replacing parts to make it work!

A Part of the video programme at the 2021 radio conference, this video tells a basic story about the SDR and DSP.

Andrew started by asking: SDR, What exactly is it?, how did it evolve, what are Hybrid SDRs, the Direct sampling limits, and more. He went on to say SDRs are part of the ‘Digital Revolution’. We might want to hang on to old LP records, but the world has gone digital. Take for instance, your phone, camera, TV or even amateur radio transceivers.  The point is that digital signal stages don’t add noise!  SDRs are a logical extension of Digital Signal Processing, or DSP aimed at converting received signals to digital as close as possible to the antenna.

Andrew went on to explain the DSP evolution and how changes were made over time to improve the result.

He explained that many amateur radio ‘DSP’ radios are not actually ‘all digital’ since the incoming signal is too high in frequency to go directly to digital due to direct sampling limits.

Amateurs who are interested in learning a bit more are recommended to watch the video, found at:   https://www.youtube.com/watch?v=jv6DCGa6zy8

A ‘boat anchor’ it is NOT!  This high quality transceiver for 80M runs a cool 400w in Class E and is small and light at only 3kg, including the power supply!  The original design was by Dave GW4GTE and the PCBs and parts were from Eric GW8LJJ. (www.s9plus.com)

Graham explained the amp’s Switch-mode has many advantages, it is theoretically 100% efficient. The audio processing uses a well tailored RMS AGC which controls maximum modulation without the usual heavy modulation transformer. Syllabic compression tracks the users voice power. A very sharp, easily tailored low pass filter keeps the signal bandwidth very well controlled resulting in excellent on air audio reports.

Graham went through each stage of the transceiver to explain how each stage operated to produce the phase width modulated signals with 100% modulation.

The receiver part of the unit is single conversion superhet allowing a choice of 80m or 160m during construction.  No special tools were required during construction but Graham did admit to purchasing an illuminated free standing magnifier (£23). He did, however, use his oscilloscope to set the PWM and drain waveforms. His shack receiver’s display was used for monitoring modulation bandwidth. A most impressive part of this build was the cost, only £347 total.

So, what to add next? CW keying and a BFO, and perhaps add a 160m matching network.

Graham felt it would make a fine addition to the GB2RS news in AM for 80m.

Robert, M0IXM was first to tell about his QCX QRP Kit.. For a start he realised there were many small parts that needed sorting and labelling. These were stored in a small components cabinet. Following the kit’s excellent instructions he soldered in the ICs followed by the resistors which all had to be soldered with one end up as there was insufficient room to lay them down on the PCB. The most difficult part was the winding of the four  inductors and the transformer. That done there were on board tools for alignment and set up. The transceiver worked without problems but the low power didn’t result in any answers. Undaunted, Rob set about sending CQ transmissions to check on the Reverse Beacon Network which showed he was copied far and wide! Success!

Don’s, G4LOO Major Project winner was the coax winder. In the past, after a contest, two persons might be needed, one to hold a pipe fed through the drum plus another to turn the drum and feed the coax on.. Short runs might not be a problem, but several runs of over several hundred feet can be very time consuming as well as tiring.  Don began to think of ways to wind automatically. Finally he settled on preformed aluminium struts to make the frame and a screen wiper motor for power. The main shaft holding the empty drum was made to access several sizes and widths and the motor speed was made variable. The finished project can be moved and powered by a tractor if required. Some photos are shown on 27th of Jan 2022 blog post.

Victor made a genuine Weekend project, a permeability tuned ATU for a long wire. Wanting to make use of a metal container from a Glenfiddich miniature, the project had to be designed to fit inside! The permeability tuner (ferrite rod) just fit the length of the box with two small capacitors to tune it from 40m to 10m, and can handle about 10w perhaps more.

Don started by presenting a dozen titles from the Convention from which to choose. The Radio War was chosen.

The video began with Dr. David Abrutat presenting information from his book, also called Radio War, telling The Secret Espionage War of the Radio Security Service 1938 – 1946. He pointed out that much of the information in public domain centred on Bletchley Park but he wanted to tell the story of the VI operators, who for the most part, remained unknown.

The video can be found at www.rsgb.org using their search facility.

This year’s Construction Contest was as well attended as most meetings nearing the end of the pandemic.

Fourteen attended to judge the five entries. This year there were no entries in the ‘Novice’ class. i.e. a member’s first entry in the Contest. However there were three entries in the Kit class. The winner was Rob, M0IXM showing his QRP Labs QCX transceiver for 20 and 40m.  The class called the ‘Weekend Special’ was won by Victor, G3JNB with his permeability tuned QRP wire tuner covering 10 to 40m at 10 watts. The ‘Major Project’ this year was won by Don, G4LOO showing his coax winding machine. As he explained in his exhibition, winding numerous sixty foot Lengths of coax after a major contest is quite a chore. This battery driven winder will do the job in minutes!

Robert M0IXM started by telling of the three ‘Cod Wars’ between the UK fishing fleet and the Icelandic ships.

His assignment was during the second of those wars when he was posted to the RV Cirolana which was co-opted to cover the fishing boat Miranda. The plan was to have three trawler support ships, two being on station in the Icelandic waters with the trawlers Miranda, Othello and Hauser. Each vessel would spend approximately six weeks on station before returning to their home port to re-stock. After each war the fishing limit around Iceland was increased to the advantage of Iceland.

Rob explained that if a trawler needed help with radio or other electrical equipment, it was planned to have sufficient spares on board to help.  However, the spares had to be transferred between the ships by Z boats (inflatable boats) The transfer was almost always during rough seas and the accompanying hazard of falling in. Robert managed to avoid the falling in.

Rob explained the method used by the Icelanders to try to cut the lines to nets being trailed behind the trawlers and how the trawler men used trawlers that were not fishing to block their access.

At the end of the evening, the cups and plaques which should have been presented at the 2020 AGM but were delayed due to the pandemic where presented.  They were:A plaque for the first ever entry in the SADARS Construction contest, to Rob Gaskell, M0IXM for his capacitive key.

The Dr. Little cup and plaque for the winner of the Kit section, to Alan Little G4PSO (no relation) for QCX QRP kit.

The Weekend Special G3DPQ cup and plaque to Don G4LOO for his Test Jig

Major Project G8EMJ shield and plaque to Don G4LOO for his ex TV cavity conversion to 23cm 500w amp.

The G3JKK shield and plaque for best club support to Brian G8GHR for his club archive and SADARS book

The G4CBI cup presented to the member who gave the best talk during the year 2020 as voted by the members, to David, G8UOD for his presentation about the Baldock Radio Station.

The Club Quiz Trophy renamed in memory of Brian Bourne  was won by the ‘Jokers 3’ consisting of Don, G4LOO, Richard, G3NII and Gareth, M5KVK. The trophy was presented to Don, G4LOO.

Eighteen members and guests were present for the dissemination of equipment belonging to former member Dennis, M0JXM who passed away on the 12th of August, 2021.  Total donations came to £108.50 which will be sent to the British Heart Foundation as requested by the family.

Regular meetings will restart on the 13th of January, 2022.

Have a Very Merry Christmas and a Safe and Prosperous New Year!