Homebrew 21 MHz Beam Part #2

Now the exciting phase, nearing the end and a moment to complete the final stages.

Construction of the matching phase, and mounting the driven element.  The antenna feed point is 28Ω, and the method of feeding the antenna is described on DK7ZM site. Once constructed from 2 lengths of 75Ω and formed into a choke this could be mounted.

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The driven element was separated with a solid plastic tube, this extended 250 mm into each side of the element. The bolts and wing nuts would provide the ideal termination point for the coax.

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The next phase was getting the aerial into the air, and checking the VSWR. The design suggested it was quite broadband, and as you can see it was 52Ω @ 21.030 MHz. A little lower than planned, but it was 1:3 at 21.250 MHz and so well within design.

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The band seemed quite lively, and we could hear a special event Indian station working a huge pile up of EU and NA. Despite calling a few times we wasnt able to make that, but a little further down the band we did hear VK and a Taiwanese (well he was from Leeds) working a few.

After finding a frequency and calling CQ we was able to work WA7M Gavin in Arizona USA.

More tests to follow soon …

73 Dave M0TAZ

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Mills On The Air 2015

Members of the Havering ARC activated 2 mills on 9th and 10th May, GB4MW at Mountnessing Windmill and GB2UW at Upminster Windmill. The call allows us to promote amateur radio to the public, and contact other people around the world.

Upminster Windmill

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Upminster Windmill operated a SSB station on 7 MHz, contacting people both in the UK and Europe and a Data modes station on 14 MHz working Europe, USA and Asia. Our furthest contact was into Australia. Working a total of 513 QSO in 39 Countries.

Here is a short audio clip of Michael M3DOV working the Special GB call

Mountnessing Windmill

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Mountnessing Windmill, GB4MW, operated on SSB and CW, concentrating on 40 metres with sporadic operation on 30, 20 and 17 metres. Most of the QSOs were around Europe, with many CW contacts into Japan and an SSB contact into Australia. From Mountnessing, we made a total of 449 QSOs into 35 countries.

In total, 962 contacts were made from both of the mills.  Further pictures of the days events have been published in the gallery.  The log books for both GB2UW and GB4MW are searchable on-line.

 

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Homebrew Project 21MHz 4E Yagi Antenna

Months ago I ordered some aluminium in preparation for another antenna project.  Wtih the assistance of John M0UKD the plan was to build a 21 MHz 4E Yagi. The aluminium was ordered from aluminium warehouse, and cost around £100 including delivery.

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The on-line shop provides and delivers lengths of up to 5 meters, and they have a vast selection of grades and lengths available.

The design was by DK7ZB and was chosen because of the short boom length and high gain. The boom is 5 meters, and made from 40mm box split into 2 x 2.5m.  The reflector is 7.2 meters long and director 2 is 6.4 meters long (to give you some scale) You will find all the measurements, VSWR and gain data on Martin’s very extensive website.

The antenna construction involves sections of the elements telescoping into each other, and Martin points out this is a critical part of the design. The aluminium was ordered with this in mind, and while some sections required no adjustment others didnt quite go to plan. We needed to “grind” some of the sections just a little, to ensure they would fit and telescope correctly. This part of the construction required 1 complete grinding disc and around 2 Hrs. work !

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Once each section that required attention was ground down, the elements were mounted on the boom. I used various places to source all the parts but some on-line resources have been linked.

As with any home construction project you always get some unexpected challenges, the first was how to get the elements to lay flat on the plastic formers. The former needs to be mounted to the boom by a nut, and this isnt easy to recess, meaning we had to cut a small hole to locate the nut into the element, allowing the element to lay flat.

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With this type of beam it presents 28Ω (by design) and so requires a coax matching section. This is yet to be constructed, but the final build phase will include this and mounting the driven element.

You can see the progress so far, and further updates and pictures will be posted once tested.

73 Dave M0TAZ
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Portable operations from Bognor Regis

Over the first May bank holiday weekend, George M1GEO took to the airwaves with his new Icom IC-7100. Running 25W, he managed some nice contacts from a family weekend away. Operating CW and digital modes (since he wasn’t allowed to make noise), George worked several DXCC entities he was missing and several special event stations.

The antenna was a 12 metre roach pole, pushed up to 5 metres, making a 1/4 wave on the 20 metre band.  A few radials were run out, as well as a ground connection to the caravan chassis.  The vertical tuned great on 14 and 18 MHz. As to be expected, 7 MHz was a little more tricky, although some contacts were made on 40 metres CW and PSK31. Tea and diet coke helped to!

M1GEO operating 20m PSK31

M1GEO operating 20m PSK31

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Operation Bunker

Havering ARC took part in Operation Bunker at the Kelvedon Hatch ‘Secret’ Nuclear Bunker this weekend. Operation Bunker was a military vehicle, memorabilia and re-enactment weekend attended by vintage military personnel from all over the South East.

We operated the bunker special call GB0SNB from beside the main mast, using SSB, CW and Data modes.  In total we contacted 368 stations in 47 countries around the world. Our furthest contact (best DX) was into Chile at 11,330 KM on 14 MHz digital modes.

You can take a look at the log (and other statistics) by clicking here. Also, some images from the weekend are in the gallery. More may be added shortly.

John M0UKD on digital modes (PSK)

John M0UKD Digital modes

Fred G3SVK on CW

Fred G3SVK on CW

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Bringing Home the Awards by Fred Curtis, G3SVK

It’s nice getting an award in recognition of time spent trawling the bands or chasing some Special Event stations, especially using very modest equipment, relatively low power and very basic antennas.

Some Clubs have an award programme that recognises the achievements of its members from construction to operating. The Havering & District Radio Club do have various awards such as the Constructor’s Cup, Chairman’s Cup, or just recognition for some outstanding contribution to the success of the Club. The Cray Valley Radio Society also has an extensive award programme and I was particularly honoured to receive two awards at their AGM this week. The first coveted award was the HF Shield awarded for achievements on the HF bands and a further award of the 40M Challenge Cup for Achievements on 40M. Both presented by the Club’s President, Bob Treacher, M0MCV (pictured on the right).

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Also during the month of April 2015, the Russian Radio Society has been operating 30 Special Event Stations to commemorate 120 years since Alexander Popov invented radio! You had to achieve more than 300 points for working each of the Special Event Stations, R120RA – R120RZ plus R2015R and R1895R. I did work them all on various bands giving a current total of 750 plus points which included other country stations such as ER120R, UP120R. The electronic award looks like this:

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So, you see what you can achieve with a bit of time, patience and skill. All these awards were achieved using only CW, but they do have SSB awards too.

73, Fred, G3SVK.

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