CHRIS M0VUE’S EXPERIMENTS WITH AN
END FED HALF WAVE ANTENNA
Plus JONATHAN G1EXG’S SHORT CIRCUIT PRESIDENTIAL PONDERINGS CHAIRMAN’S CHATTER SOME ASPECTS OF AMATEUR RADIO LIFE BY ALAN G4GNX RALLIES
Spring 2017
Worthing & District Amateur Radio Club Established 1948 Website: www.wadarc.org.uk
E-mail: info@wadarc.org.uk President: Chris Smith G3UFS WADARC meets every Wednesday at 8pm in the Lancing Parish Hall, South Street, Lancing BN15 8AJ. All who have an interest in radio communications and associate subjects, whether a licensed amateur or not, are invited. WADARC can also arrange training for the radio amateur Foundation, Intermediate and Advanced licences. The WADARC Committee 2016 - 2017 Andrew Cheeseman Alan Baker Alastair Weller Sally Holland Andy Braeman Ian MacDonald Chris Suddell Norman Jacobs
G1VUP G4GNX M0OAL SWL M6RFE M0IAD M0VUE 2E0RKO
Chairman Vice-Chairman Secretary Treasurer Quartermaster Membership Secretary Member Member
These Members have volunteered to accept these responsibilities for 2015 - 2016 Contest Manager Ragchew Editor Training Coordinator Website Website Website
Graham Bubloz Roger Hall Andrew Cheeseman Alan Baker Alastair Weller Andrew Cheeseman
G4FNL G4TNT G1VUP G4GNX M0OAL G1VUP
WADARC Club Nets (all times are local) 07.30
Sunday
3.725MHz Âą QRM SSB
19.30
Monday
145.425MHz (V34/S17)
11.00
Thursday
7.106MHz Âą QRM SSB
CONTENTS
Editorial .......................................................... 4 Chairman’s Chatter ........................................ 5
Presidential Ponderings .................................. 6
End Fed Half Wave Antenna by Chris M0VUE ..... 8
Short Circuits by Jonathan G1EXG ......................... 14
Aspects of Amateur Radio Life by Alan G4GNX ... 16
Rallies ............................................................ 21
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EDITORIAL elcome once again to the latest edition of Ragchew. It’s taken a while but thanks to some very welcome last-minute contributions, we now have another edition. Because it’s proving to be very difficult getting members to send in enough to fill each issue, it’s not been possible to keep to specific publication dates so I’ve simplified things a bit. Instead of putting months on the covers, I’m trying putting seasons– it’s still in keeping with having quarterly issues and it saves confusion when the actual publication date does not match the cover date. Hence, this is the Spring edition.
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In This Issue There are no Committee Minutes or Club Calendar this time but there are reports from President Chris G3UFS and Chairman Andrew G1VUP. They’re followed by an interesting article from Chris M0VUE. He’s just built his first end fed half wave (EFHW) antenna for 20m and although at first it seemed it was going to be easy, he soon found he had some very high impedance to overcome. He did it and now he’s looking forward to building base and mobile versions for different bands. In his Short Circuit column this time, Jonathan G1EXG looks at another high impedance antenna, the folded dipole, and explains that despite the extra materials, complexity and expense involved, there are some advantages to using it. Our final article is by Alan G4GNX. It was inspired by a conversation he had in the clubroom one evening and in it the topics he covers include Repeaters and the ‘K’, SSB (Non-Split) Operating, Planning Permission and Interference and finally, Amateur Radio (UK) Licensing. If any of Alan’s comments inspire you to reply, please do. Please send your thoughts on them or anything else you’d like to see in Ragchew to me at ragchew@wadarc.org.uk My sincere thanks go to everyone who contributed to this issue because Ragchew wouldn’t be here without them. 73, Roger G4TNT
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CHAIRMAN’S CHATTER
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ello and welcome once again to another Ragchew and another Chairman’s Chatter. First off, I must apologies for missing the last two Ragchews. However, if you were at the Club meeting on March 15th you will know that for me, life has been getting in the way of Club business recently and I’ve had very little time to spare. Fortunately, things have quietened down now and I’m hoping I will be able to dedicate more time to the Club over the coming months. Club Activities We are just about to start the Club activity season and two events I always like to see the Club take part in are the PW QRP 144MHz Contest on June 11th 2017 and SSB Field Day on September 2nd & 3rd 2017. Please let us know if you’re interested in taking part in either of them – they’re always enjoyable In addition, Special Event Stations are planned for Mills on the Air (May 13th & 14th), the Worthing Fire Station Open Day (July 22nd) and International Lighthouse Lightship Weekend (August 19th & 20th). Again, we do need people to be involved so please volunteer if you’re at all interested or just come along to see what goes on at these events. Club Shack The Committee is still working on a better shack solution for the Club. I know there has been a fair bit of chatter on ‘what and where’ so let me try to clarify the situation by saying that no decision has been made nor has any real option been offered. We are still looking and are open to any ideas so please tell us if you think you know of somewhere suitable. Finally I also aim to get back on the air shortly and I hope to be able to join you on the Sunday net soon. Until then, 73 for now, Andrew G1VUP
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PRESIDENTIAL PONDERINGS
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ere we are again, the start of a new year, 2017. I wonder what it is going to bring us, probably more restrictions along with less money to improve on the poor standard of living we have. However, we are a resilient nation so I expect we will muddle through. At this point, may I wish you all and your families a very belated Happy New Year – in spite of what I have just written! The Club is still doing well and attracting new members, which is a very good thing. I think we must be the most attractive club in Sussex! However, I do feel we have to find more ways of keeping those new members with us by providing activities that we can get them to participate in. I appreciate this can quite difficult to do at this time of the year when there are fewer outside activities and constraints on what we can do in the Parish Hall rooms but maybe we should try. RAF Reminiscences I was recently reading about all the security measures currently being put in place in our lives and it reminded me of the security and checks I had to undergo whilst in the RAF in Germany back in 1952. After passing out of Trade School as a Wireless Operator, I was told that I would be joining the ‘Met Scheme’ (Meteorological Scheme, obviously something to do with the weather) and that I was going to be posted to Germany instead of to Habbaniyah near Bagdad, which is where it was originally intended I should go. Whilst at the Personnel Dispatch Centre at Lytham, a message had me report to an Orderly room where I was met by a gentleman in civvies! This gentleman introduced himself as a Warrant Officer in the RAF and he said that he needed to ask me some important questions, including details of my family, even my grandparents, their religions and political views such as had they ever been in the Communist Party and so on! At this point I had no idea why these questions were being asked but all became clearer when I was told to sign the Official Secrets Act (which I still have a copy of) and informed that I was going to a highly secret
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C Signals unit in northern Germany, near Hamburg and quite close to the East German border. This later turned out to be 365 SU, a ‘Y’ Service operation – the name derived from Wireless Interception (WI) – that involved listening to members of the Eastern Block. I spent fourteen months doing my part in this operation, two days on, two days off, seven days a week, listening mostly to Morse code but occasionally there were voice communications that were transferred to translators. All the time I was there the security was incredibly intense. An example of the security at the Station was the check made every time anyone entered the communications area. They were stopped at a heavy mesh gate at the top of the stairs by an armed RAF policeman who demanded to see their 1250 (identity card). It transpired that even the Officer commanding the Station was not allowed into this hallowed place of listening if he hadn’t been cleared to a certain level of security. When I left RAF Uetersen in 1953, I once again had to sign another copy of the Official Secrets Act and told in no uncertain manner that I was not to say anything to anybody about what I had been doing at Uetersen, not even to my family. It is only recently that this restriction has been relaxed. I hope you have not found the above chat about my past in the RAF too boring but I’ve found as you get older, memories return and in some cases one feels the need to let other people know what happened way back then. 73, Chris G3UFS Illegitimi Non Carborundum Est
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ANTENNA PROJECT End Fed Half Wave Antenna Chris M0VUE decided to experiment with an interesting antenna for 20m but soon found that although it initially seemed simple, he first had to overcome some very high impedance. For some time now I’ve been looking to build some end fed half wave (EFHW) antennas for portable use because they are cheap, efficient and quite simple to make. My first one, which is for 20m, cost just £11. If you’re not aware of the EFHW antenna, it’s basically a dipole fed from the end, simple – well not quite so simple in practice. Due to the antenna being feed from the end, you have a very high impedance to deal with, typically between 3.5kΩ and 5kΩ (more about that later) which you need to match to your coax so you have to bring the impedance down to 50Ω. To match the impedance, I found I needed to build a matching LC circuit. There are many ways to make the match but I chose the method from the very informative http://www.aa5tb.com website. If you want to read all about EFHW antennas, go there and have a look. You’ll find many pages on the subject. Apparently, the design shown below is about 95% efficient so in theory 95W of my 100W might radiate from this antenna. For a ¼ λ antenna, at best you get 50% with 64 radials in the ground.
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C Construction I started with a T200-2 torrid from which I made a 1:8 turn primary to secondary ratio, as shown in the photo. I used enamelled copper wire for the secondary and some thick multistrand wire for the primary winding. I picked the large torrid and thick wire because I was going to use 100W from the radio. I rigged up a 3.2kΩ resister between the ground and live of the antenna to test the LC circuit. I chose a 3.2kΩ resistor because an EFHW matched with an LC circuit comes in lower than the 5kΩ most people quote. The Finished Transformer I found this little table to be useful for picking the correct resistor. It shows the turns ratio formula TR = √(Za/50) 6:1 for Za = 1800Ω 7:1 for Za = 2450Ω 8:1 for Za = 3200Ω 9:1 for Za = 4050Ω 10:1 for Za = 5000Ω Testing Setup To tune the circuit and measure the required capacitance I used a variable capacitor with the resistor in place and my antenna analyser set to 14.175MHz checking the circuit. I turned the capacitor until my antenna tuner dipped at 14.175MHz and I had an SWR under 1:2 across the 20m band.
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C I then unsoldered the variable capacitor and measured the capacitance setting to give me a rough guide for the capacitance needed for the finished circuit. This capacitance worked out to be about 35pF. Making the Capacitor Next I looked up the capacitance of Mini 8 and found it to be 80pF/m so I decided about half a meter of cable should do it. I cut this off then trimmed it down to length. I then realised I’d knocked the variable capacitor and then I ended up with about 24pF needed, which was about 30cm of cable. I connected this up, tested it by trimming the capacitor and put it in a box. I then cut 10.5m of cable for the antenna and 1m for the counterpoise. When set up, I cut the antenna until I had as close to zero reactance to the antenna or, in other words, the antenna was resonant at 14.175MHz. Now, the antenna has an SWR of less than 1.5 across the whole band. EFHW Antenna as a Vertical The theory behind this antenna says that if it’s properly installed as a vertical, you will get a radiation pattern like this.
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C You can see from this there is very little gain, about 1dB, but most of the Inverted V(ish) radiation is at 16.8°, which makes this is a very good antenna for DX. However, when I originally mounted it in the garden, I used a 6m fishing pole and it looked like the model shown left, with the feed about 1m off the ground, up to the top of the pole, then across to my observatory. The radiation pattern is now different, as you can see here.
Ok, it’s now not ideal as a DX antenna because most of the radiation is now up 84° but having said that, in this configuration I did manage some good DX with the following QSOs made during the test cycle.
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C Look up YC8RBI if you get a chance. I certainly enjoyed being the first to reply to his CQ call! So, the antenna now works. Since I carried out the original test, I’ve not left the antenna set up and now I have a 12.5m fibreglass pole that I push up when I want to use the EFHW antenna on 20m. The finished installation can be seen in the photos shown here.
The finished box strapped to a post at home.
The EFHW antenna set up at home.
The fibreglass is grey so 90% of the time you cannot see it. I had to wait for a sunny day to get this picture. I tried the EFHW antenna today in this configuration and although conditions were, at best, bad, I did manage to make the contacts shown in the table on the next page.
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What Next? I’m currently building a QRO 400W 20-40-80m EFHW for home along with a QRP version for mobile use. However, these will use a different design with different cores and coax traps for the QRO version and LC traps using T68-6 cored for the portable antenna. Watch this space. 73, Chris M0VUE
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G1EXG’S SHORT CIRCUITS This time Jonathan G1EXG explains why, despite its complexity, there are some advantages to using a folded dipole antenna.
Short Circuit No. 14: The Folded Dipole The folded dipole is a full wavelength of wire folded around on itself so that end to end it is a half wavelength long - the same length as a standard dipole. There is no gain over a standard dipole so why should we bother with the extra complexity, materials and expense?
The first reason is that the feed impedance is higher than the standard dipole, which can be useful (see below). The folded dipole is fed at the centre of one of the parallel wires but because the current is shared with the adjacent parallel wire, the feed resistance will be four times that of a standard dipole (about 300Ω instead of about 75Ω). Therefore, you can conveniently make (and feed) a folded dipole from lengths of 300Ω twin feeder. Another plus for the folded dipole is that it has a larger bandwidth than the
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C standard dipole. Here's why. You can imagine the folded dipole to be made up of two quarter wave sections connected either side of the feeder. Each folded half is a shorted quarter wave matching section. Now a shorted quarter wave length of line looks purely resistive (high resistance) at resonance but slightly inductive when its slightly short (i.e. slightly low of the resonant frequency) and slightly capacitive when its slightly long (i.e. when it is slightly high of the resonant frequency). This is exactly the opposite of a non-folded dipole response. Therefore, the result is that in a folded dipole, the departure from pure resistance - slightly off-resonance - is compensated for a little by the folded halves, creating a greater overall bandwidth than a standard dipole. Bands that span a relatively large range of frequencies (like 80 or 10m) need a wideband antenna to cover the whole frequency range. In this case a folded dipole is a better choice than a standard dipole. The second reason is that the antenna is a complete loop so you can pass a DC current up through the feed line to heat the wire slightly to melt snow or heavy ice that might detune, droop or even break a long antenna (e.g. for top band). A broadcast station, for example, could use inductors to allow a small continuous DC current to pass even when transmitting through the antenna. Another reason is that folded dipoles are useful devices to use in Yagi antennas. The reflector and director elements drop the radiation resistance of the dipole to a very low resistance, which is difficult to match directly to coax. Folding the dipole will multiply this by four and that can often provide a good match to 50â„Ś. It is often possible to arrange things so that the folded dipole resistance will drop from 300 to about 200â„Ś. A halfwave balun (which has a 4:1 impedance ratio transformation) can then give a good match to 50â„Ś coaxial cable (200/4 = 50). I have used this on many 2m and 70cm antennas. Finally, the centre of the element opposite the feed point in the folded dipole is at zero voltage. This means a folded dipole can be attached directly to a metal mast at this point, providing an extra secure fixing and mechanical stability. As this point is a direct DC connection to ground (if the mast is earthed), it provides some lightening protection for your radio and helps to reduce static electricity build-up. 73, Jonathan G1EXG
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FEATURE Some Aspects of Amateur Radio Life Alan G4GNX expands on a clubroom conversation he had recently and then he shares some of his thoughts on amateur radio operating.
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few weeks ago, when I was chatting to Norman 2E0RKO, I happened to mention what the ‘K’ sent by repeaters is for. He said that he hadn’t known that before and suggested I write it up for the benefit of other members who also might not know so here it is, plus a lot of extras. Repeaters and the ‘K’ Even if you have not studied Morse code in any way, you still might know that there are many short sequences of characters and single letters that are used as protocol signals and short-form ‘words’ to save sending time. Abbreviations such as QSO, QTH, DX and so on will probably already be familiar because they have carried over from CW operation into everyday ‘ham’ speech. However, some things have not transferred in this way, one of them being the single letter ‘K’ - the invitation to transmit. The speech equivalent would be “over” or perhaps “back to you” or “go ahead” and sometimes “break”, meaning “I have finished what I want to say (for now) and it’s your turn to transmit”. Most UK repeaters use some form of signal to indicate that one person has finished and it’s okay for someone else to transmit. The most common of these is the letter ‘K’ sent as Morse code (Dah De Dah) and it’s known as the ‘K break’. What you might not have realised is that there is a deliberate time delay between the sender’s carrier being dropped and the letter ‘K’ being sent. This short pause is to allow others to break in and you should not try to beat it! Of course, there’s also a delay after the ‘K’ to allow the next person to transmit, before the repeater drops its own carrier. There’s plenty of time to start your transmission without needing to dive in before the ‘K’ and
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C it’s just plain good manners to leave that ‘K’ break. With some repeaters there is a time limit on the length of a single transmission (times vary from repeater to repeater) and the sending of a ‘K’ indicates that the timer has been reset for the next transmission. In this case, if you dive in with anything longer than dropping your callsign in or yelling “break”, you run the risk of exceeding the time limit and your voice being cut off in mid-sentence. By doing this, you not only occupy the repeater without being heard but nobody else can use it either. Despite all of the above, please don’t be put off using repeaters (especially GB3WO). If we all give a little thought to how we’re operating, everyone can live in relative harmony. SSB (Non-Split) Operating Even some old timers don’t seem to understand the correct way to tune their transceivers when using SSB. I hear operators saying things like, “I’m on 144.310MHz so if you tune your dial to that readout, we will be in tune with each other.” No, you won’t necessarily be so! Here’s why – the generally agreed protocol is for one station to make an initial call (CQ) on the frequency of their choice. If this is a net frequency that’s been published, they should attempt to be as close as possible to that frequency. However, when you try to do this, unless you have a very accurate frequency counter, you might find that the readout on your rig is slightly out with the actual frequency you think you’re on. This is not something to worry about unduly and provided you’re not right on the band limit, this really doesn’t matter for normal SSB operating. Someone else will now (hopefully) answer the initial call and they should have tuned their transceiver so that the received audio sounds natural and undistorted (not Donald Duck-ish), having first ensured that any RIT/XIT or other frequency shifting controls are turned off! Provided none of the transceivers are poorly aligned internally, transmit and receive should track each other and it does not matter if
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C the frequency readout on your rig is not what you expect it to be. Most modern frequency readouts tend to be digital and, unfortunately, there are many pedants out there who will throw a hissy fit when the digits don’t match. Once again, it does not matter! As long as you’re in-band and the station you’re replying to sounds natural, you’re all set. You might be wondering why it is that when you listen to several stations in a net, many sound as though they’re on different frequencies. There could be several reasons for this. Sometimes it’s due to one or more stations not ‘netting up’ on the initiating caller and then, perhaps, other stations ‘netting up’ on one of them instead of on the initial caller. It could be that one of the transceivers has drifted in frequency or it could be that one or more of the transceivers is out of alignment (transmit and receive are offset). To make sure everyone is in tune, the sensible procedure when joining an established net is to listen for the net controller and tune your receiver so that they sound right to you. After that, do not retune your main dial for any reason. If any of the other stations don’t sound right to you, use your RIT (Clarifier) control to tune them in without moving your transmit frequency. If you move your main dial, you end up with stations chasing each other up and down the band, all complaining that xyz is off frequency. That’s just plain bad operating. I’ve even made an initial call and been told, “You’re off frequency!” Ermm… excuse me – what frequency should I be on? Provided I’m transmitting in-band within my licence conditions, I’m on the frequency I want to be on. Just because your receiver’s readout doesn’t agree with what you think it should be, not being a mind reader, it’s not my problem! One more minor rant about transmitter/antenna tuning – please remember that you should do so on a clear frequency. In practice, this means that if you’re about to call a station you’ve just heard, when you tune you should be at least 3kHz away from them to avoid interference.
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C When you move frequency back to the received station, your SWR really won’t change enough to matter. Planning Permission and Interference Following a minor argument between me and AN Other, I’d like to put the record straight on dealing with local councils when you’re making a planning application for an antenna installation. Whilst it is always best to be polite to councils/planning officers and to deal with in a professional manner, occasionally you’ll find one of them will overstep the mark (usually through ignorance) and they might factor something into their judgement that they should not. Possibly the worst thing for radio amateurs is when a planning application is considered partly on grounds of interference, especially if there has been an objection on those grounds. It needs to be made quite clear that councils/planning officers should never factor interference into their judgement, simply because they are totally unqualified to do so! Planning permission must be granted or denied on grounds of aesthetics, safety and other factors covered by local byelaws and in the UK, there are no local byelaws that cover RF interference. If there were, radio amateurs would be using them in reverse to have other peoples’ badly installed solar panels, LED lighting and broadband et al removed and Council Tax would increase due to the additional workload! If a member of the public has an interference issue, their first port of call is the BBC and later perhaps Ofcom. For either of those bodies to act requires that the interference actually exists and can be proven. They will not act because interference might occur. Local councils are almost certainly aware of this but sometimes they choose to ignore it and thereby exceed their own authority. Apart from informing a council that it is plain wrong to consider interference (some will take a lot of convincing), it’s probably best in these cases to consult the RSGB because they have volunteer experts
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C who are willing to help with planning applications and with interference issues. Despite cynicism by some, the RSGB will step in to help, although they may not act as quickly as some would prefer (yesterday!), depending on the severity of the case. Amateur Radio (UK) Licensing There has been some discussion on internet forums regarding amateur radio licence fees. Some people (especially the less well-off and some who are downright mean) are quite happy with the current situation of no fee, whilst others (me included) would prefer that a modest licence fee should be charged. One of the arguments against a licence fee is that any sort of fee would be some discouragement to prospective licensees, but nobody seems to know how great the effect might be. The main argument for having a licence fee is that we would be paying for a service and that might give us more ‘clout’ when trying to get Ofcom to act on our behalf. Again, nobody really knows how much ‘clout per buck’ this might give us. If the majority of WADARC members were to vote in favour of a licence fee being charged, should we as a club pursue this with Ofcom and the RSGB and if so, what would be a suggested amount? Food for thought, I hope. Please do write in to Roger at Ragchew (ragchew@wadarc.org.uk) with your feedback on this or anything else you’d like to see discussed in these pages. 73, Alan G4GNX
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RALLIES 2017 APRIL 2nd – Hack Green Bunker Rally Hack Green Secret Nuclear Bunker, Nantwich, Cheshire CW5 8AL 9th – NARSA Exhibition (Blackpool Rally) Norbreck Castle Exhibition Centre, Blackpool FY2 9AA 23rd – Ripon Radio Rally Hugh Ripley Hall, Ripon, North Yorkshire HG4 2PT 23rd – Yeovil QRP Convention Digby Hall, Sherborne, Dorset DT9 3AA 30th – Cambridge Repeater Group Rally Foxton Village Hall, Hardman Road, Foxton, Cambridge CB22 6RN 30th – West London Radio & Electronics Show (Kempton Rally) Kempton Park Racecourse, Staines Road, Sunbury on Thames TW16 5AQ
MAY 1st – Dartmoor Radio Club Rally Tavistock College, Crowndale Road, Tavistock, Devon PL19 8DD 6th – Sussex Electronics and Radio Fair (SERF 2017) Eastbourne Sports Park, Eastbourne, East Sussex BN21 2UF 7th – Dambusters Hamfest Thorpe Camp Museum, Tattershall Thorpe, Coningsby, Lincolnshire LN4 4PE 7th – Scottish Amateur Radio & Electronics Convention Braehead Arena, Kings Inch Road, Glasgow, G51 4BN 14th – Lough Erne Amateur Radio Rally SHARE Centre, Lisnaskea, Co Fermanagh, Northern Ireland BT92 0EQ 19th to 21st – Dayton Hamvention Greene County Fair & Exposition Center, Xenia, Dayton, Ohio, USA
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C 20th – RADARS Flea Market Indoor Sale St Vincent de Paul’s, Caldershaw Rd, Norden, Rochdale OL12 7QR 21st – Dunstable Downs RC Annual National Amateur Radio Car Boot Sale Stockwood Park, London Road, Luton, Bedfordshire LU1 4LX 28th – Durham & District ARS Radio Rally Bowburn Community Centre, Co Durham, DH6 5AT 28th – Causeway Coast Glens ARC Radio Rally Bushmills Community Centre, Dunluce Road, Bushmills, Co. Antrim BT57 8QG
JUNE 4th – Spalding & DARS Annual Rally The Sir John Gleed Technology School, Halmer Gardens, Spalding PE11 2EF 4th – Red Rose QRP Festival The Rose Centre, Hesketh Meadow Lane, Lowton, Warrington WA3 2AH 11th – Junction 28 Rally Alfreton Leisure Centre, Church Street, Alfreton DE55 7BD 11th – East Suffolk Wireless Revival (Ipswich Radio Rally) The Orwell Crossing Lorry Park, A14 Eastbound, Nacton, Ipswich IP10 0DD 17th – South Lancs ARC Summer Rally Bickershaw Labour Club, Bickershaw Lane, Bickershaw, Wigan WN2 5TE 18th – Newbury Radio Rally Newbury Showground, next to Jcn 13 of M4, Berkshire 25th – West of England Radio Rally Cheese & Grain, Bridge Street, Frome, Somerset BA11 1BE
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