The “Skills Evening” held on 18 October proved to be very popular, with one of the highest attendances so far this year. Six members manned tables around the room to demonstrate, explain and talk about an aspect of amateur radio – usually one which was a particular interest of theirs. Ken G3LVP explained how make properly make-off coaxial connectors such as BNC and N-type, with examples and supporting diagrams. Peter G3YJE demonstrated a “Tuna-Tin” QRP transmitter, showing the output waveform on a ‘scope. He was also promoting the American Radio History website to which he has been contributing for several years. Paul 2E0IFV had a display of DMR radios, including hand-helds, and demonstrated their use. Tony G3SNN showed his fine collection of exotic QSL cards for his 160m and 6m activities. Barry M0HFY had a live demonstration of FT8 (one of the latest data-modes which is currently very popular), making several contacts during the course of the evening. Mike G4GUG was extolling the virtues of Linux, and telling how well this Operating System would run on older machines. Each of the tables attracted a gathering of members for much of the evening, and much general and lively chat took place as well. Very many thanks to the six members who kindly “volunteered” to man the tables and indeed to everyone else who made an appearance; you all contributed to the undoubted success of the meeting. We were pleased to enrol Chris M6NZC as a new member and John 2E0GCR who re-joined after an absence of a year or two. Thanks once again go to Alan M0NRO for kindly manning the kitchen. Thanks also to the several members who, without being asked, helped clear away the tables and chairs at the end of the evening – your efforts are much appreciated.
Last month we were pleased to welcome back Peter G3RZP, a well known speaker at amateur radio functions – at local, national and international levels.
The title of his talk was “Clean Signals” and he proceeded to tell us why transmitters, and SSB transmitters in particular, emit signals which are much wider than they should be – and so cause interference to stations on adjacent frequencies. SSB transmitters are essentially “linear” amplifiers, amplifying a signal generated at low-level up to the desired power required for transmitting a signal to wherever. However, the amplification process is not actually truly linear because of the inherent characteristics of the active devices, be they thermionic valves or solid-state devices. In an SSB transmitter the non-linearity gives rise to what are known as “intermodulation products” which spread out either side of the main signal. Intermodulation products are, in the simplest case, caused by two discrete signals being amplified mixing together, because of the non-linearity, to produce low-level signals spaced from each other by the difference in the frequency of the two signals. The further away from the main signal the weaker these products become. But even low-level “spurii” can cause QRM to near by stations.
So the way to minimise such interference – sometimes called splatter – is to make the transmitter/amplifier operate as linearly as possible. This can be done by making sure that the equipment is not over-driven – ie by not turning the mic gain up too far, by using minimal amounts of ALC and by making sure that the transmitter sees the correct load impedance. In the design stage negative feedback can be introduced to improve linearity, but this can cause other problems if not done carefully. One way to check that the transmitter is being operated corrected is to inject two audio tines into the mic socket and look at the RF output with a suitable ‘scope, the tops and bottoms of the waveform seen should be nicely rounded. Peter’s view was that in general valve amplifiers are inherently more linear than solid-state ones.
The talk was well received to judge by the number of questions asked. Many thanks to Peter for travelling from Swindon to see us once again.
A good turn-out of members enjoyed an interesting display of exhibits from members’ radio rooms (or shacks if you prefer!). The exhibits ranged from early types of detectors of radio signals to a modern piece of kit to power radios from solar energy. Also on display were a selection of old QSLs cards, an Elecraft Miniature ATU, a once popular IC-202 portable 2m SSB rig from the past, a Retevis RT82 DMR hand-held, a portable station in a box and a dog! To add further interest to the evening Mike G4GUG gave a short talk on how to set-up a rotator for satellite working.
Many thanks to everyone who brought along something to show, to Mike for his talk and to Peter G3YJE for manning the kitchen (yet again!).
Several members attended the Thursday evening meeting to listen to Colin G3VTS and Jon M0JMM talking about the construction of their antennas.
Colin who was awarded the G5BK cup at the Constructors’ Exhibition for his 5 band cobweb antenna. He described his cobweb as 5 dipoles in a square shape with 1⁄4 wave sides with the feed point in one corner. The impedance was found to be about 12 ohms needing a 4:1 balun to match 50 ohms coax cable. Colin made good use of a projector and photographs he took during the construction period which took place in his garage and then testing it on the garage roof. He found that the bandwidth was narrow and although no DX was worked, Colin will no doubt be tweaking it leading to further trials in the future.
The second speaker Jon, talked about his 2 metre 3 element Yagi antenna manufactured from a Tape Measure, plastic water pipe, Jubilee hose clamps and a small piece of wire to form a match to 50 Ω coax cable. The tape was cut to lengths suitable for the driven, reflector and director elements, with the driven element cut in half to form the dipole. They were mounted on the plastic tubing to form the Yagi antenna using the hose clamps to hold them in place. At the dipole centre, a hairpin match and the coax cable were soldered to the centre of the dipole. For more information on construction and dimensions of this antenna, look up “Tape measure antenna”.
Jon said that it was ideal as a DF antenna for fox hunts because it was portable, light weight, had a good front to back ratio, a reasonable gain and above all cheap and easy to make.
The talks were well received by the members and it was good to see that the spirit of ‘homebrew’ is still alive !
The meeting started with a mini-auction of kit from the shack of the late M0ITF. There were bargains to be had and several members went home with some useful goodies. However the reserves were not met on the more valuable lots so these will be sold by other means, including rallies. Many thanks to everyone who supported the auction, and particularly to Mike G4GUG for doing a super job as the “porter” holding up and describing the various lots.
The second part of the meeting was a session by Barry M0HFY on PSK. He spoke about the various forms of this particular data-mode and illustrated how it could be used with the HRD logging program. A very interesting talk, supported by good screen-shots, even for those like me with little or no intention of trying the mode! The talk greatly improved our knowledge of PSK and we’re very grateful to Barry for his time and trouble.
A brief survey of members’ opinion on the suitability of the venue for our regular monthly meeting indicated a preference to remain at Brizen.
Thanks also go to Colin G3VTS for manning the kitchen.
On Thursday 15th March we held our annual Constructors’ Exhibition preceded by a short auction. It was a really great meeting, with one of the best attendances for a very long time.
The meeting commenced with an auction of 15 lots from the shack of late CARA member Ian M0ITF. Our Chairman Tony G3YYH did a super job as auctioneer extracting bids with much skill and humour. Every lot was sold, some at higher than expected hammer prices. Ian’s family were well pleased with result.
The Constructors’ Exhibition was fairly well supported but with fewer exhibits than in recent years. Nevertheless there was much of interest to look at. The Morse Keys made from clothes pegs by Jon M0JMM attracted much attention and really should have won a prize had there been a suitable category! Two pieces of home-brew from the early 1970s, built by Ken G3XSJ, also attracted much attention – as being examples of construction techniques from yesteryear. The “741” op amp constructed from discrete components by Simon G4SGI was considered an excellent teaching aid. The Tuna Tin transmitter for 40m fascinated many.
The well deserved winner of the Bill Brown G5BK Cup for “Best in Show” went to Colin G3VTS for his home-constructed 5-band cobweb type antenna – exhibited as photos rather than the real object! The Pat Moore memorial Cup for “Innovative Construction” and the Roger Kendall G0UPU Memorial Cup for “Best Software or Computer Related Project” were not awarded as there were no suitable qualifying exhibits. The judges were Peter G4ENA and Ken G3LVP to whom go many thanks.
Here’s a full list of exhibits, in no particular order:
HF2V shorting strap for 30m operation – Tony G3SNN.
Selection of Morse Keys made from clothes pegs – Jon M0JMM.
KRC-5 80m direct conversion receiver – Derek G3NKS.
5-band cobweb antenna – Colin G3VTS.
Audio modules for 6cm wide-band FM transceiver – Stewart G0LGS.
160m valve transmitter 1971 – Ken G3XSJ.
PW Clubman receiver 1970 – Ken G3XSJ.
Tuna Tin 300mW transmitter for 40m – Walt G3NYY.
Discrete “741” op amp from a Mad Scientist kit – Simon G4SGI.
On display but not in the formal Exhibition:
An unfinished 4-band 45W transceiver – Colin G3TA.
Many thanks to everyone who helped to make it such an enjoyable meeting, and particularly to auctioneer Tony G3YYH, and to Peter G3YJE, Alan M0NRO and Smurf M0URF for manning the kitchen.
The meeting started with a short auction of Silent Key items. There were about a dozen lots including an elderly FT-102 HF transceiver, an external VFO and speaker units for the FT-102, two scopes, two AVO multi-meters and two power supplies. A couple of the lots failed to reach their reserves but the rest went for good hammer prices (for the benefit of the family).
The main activity that evening was the “Table Top Sale” where members brought along items no longer wanted to sell. There was plenty of interesting stuff up for grabs, some at very low prices, Andy M0JLY was disposing of several of his home-brew projects several of which were quickly snapped up. Other sellers included Tony G3SNN, Colin G3VTS, Jon G0FJT and Peter G3YJE (apologies to anyone missed). Reports suggest that both sellers and buyers were pleased with the outcome even though some of the tables didn’t empty as well as was hoped. As usual there was lots of chat – it’s great to see members getting together seeking advice, swapping stories and enjoying each others company. Surely that’s what clubs are all about! Finally, many thanks to Colin G3TA for manning the kitchen.
The meeting saw one of the largest attendances for a talk for some time, no doubt because of the popularity of the subject matter, Data Modes, and the speaker, Barry M0HFY.
The meeting began with a couple of presentations carried over from the AGM in December.
The Bernard King G3CEG Memorial Cup, for noteworthy and praiseworthy on-the-air activities went to Simon G6AHX in particular recognition of his VHF DX successes.
The John Holt Award, for exceptional services to the club, went to Jon M0JMM in particular recognition of his work creating and managing the CARA Fun Activity Challenge.
Barry began by explaining how radios and computers could be connected together for working data modes, starting with the simplest form of inter-connections to more sophisticated arrangements using interface units. He then spoke about popular modes such as JT65 and FT8 – noting that the latter is rapidly becoming the data mode of choice for very many operators. Several screen-grabs of JT65 and FT8 in action where shown. A fuller report will appear in February’s CARA News.
Many thanks to Barry for a really interesting talk, as evidenced by the many questions asked of him, and to Alan M0NRO for manning the kitchen.
This is a brief report on the AGM. A fuller report will appear in an early issue of CARA News.
Twenty-five members and one visitor (who subsequently signed-up as a member) attended the meeting.
The minutes of the 2016 meeting were approved followed an amendment
The Chairman’s and Treasurer’s reports were approved unanimously.
The proposal to keep the annual subscription at £13 was approved.
The following were elected unopposed to serve on the committee for 2018:
Chairman: Tony G3YYH
Secretary: Derek G3NKS
Treasurer: Peter G3YJE
Committee members: Christopher M0YNG (Editor of CARA News)
Graham G8URP who will continue to act as Membership Secretary.
Accounts Examiner (non-committee post): Tony G3SNN
It was suggested that the club should buy equipment, especially test gear, for loan to members. Another suggestion was that a survey of members’ opinions about the club and its activities should be conducted. The Chairman said both these suggestions will be considered by the 2018 Committee.
It was confirmed that the committee was still seeking a better venue for our monthly meetings, two had been considered but rejected as being unsuitable.
The meeting closed at 20.18 following a vote of thanks to the committee for doing a good job during 2017.
After the formal meeting, we enjoyed much chat and a generously provided finger buffet and a bar.
The “bring and show something from your shack” meeting on 19th October produced a wide and fascinating display of exhibits. Here’s a list, in no particular order, of the items on show and their owners:
Baofeng 70cm handheld costing £15 new! Graham G8XRS.
Tytera MD-380 DMR radio talking to a Bluestack hot-spot. Malcolm G0TMP.
GCR9 (“Angry 9”) military HF AM/CW radio, Codar AT5 (160 & 80m AM/CW transmitter) with PSU, Heathkit HW-9 QRP HF CW transceiver with tuner and watt meter, Heathkit HW-12 80m SSB transceiver, laptop accessing old radio magazines. Peter G3YJE.
Pye PCR2 (WW2 vintage LW/MW/SW “domestic” receiver as used in NAAFIs etc). Derek G3NKS.
Vertical hand-drill, modified for some unknown purpose (any suggestions?) Tim G8PZD.
Icom IC-706 HF transceiver with matching unit and power supply. Christopher M0YNG.
High Power ATU type BC-939A for BC-610 AM transmitter, ex-US military. Tony G3YYH.
ETM9COG Morse memory keyer, paddle and Morse reader. Giles G0NXA.
Step-ladder steady made using scaffolding clamps bought at a recent CARA sale. Small computer HP260. Colin G3VTS.
Display of Morse paddles, mostly home-constructed. Colin G3TA.
FreeSat receiver type V7HD, costing £20. Simon G6AHX.
Demonstration of how to unsolder quad packaged ICs using “magic” metal. Ken G3LVP.
A good evening with much interest being shown in the exhibits – and lots of chat.
Many thanks to Tony G3YYH for manning the kitchen.