AmateurRadio.com

Today I replaced the home made 2m Moxon Rectangle with a Vine Antennas SuperMoxon. As you can see from the picture of it installed in my attic it is a Moxon Rectangle with two directors that are also folded into a rectangle.

My attic, like my house, is very small. As is usual with modern British houses, the roof trusses are made of thin wood with cross-bracing for strength, so the attic area isn’t open to allow the free rotation of antennas. I have crammed rather a lot of antennas into this space to try to cover the maximum number of bands, so the VHF antennas have been forced into odd corners. Using a conventional small beam is not possible as there is insufficient space to allow rotation.

Vine Antennas claim that no other antenna gives so much gain in such a small turning circle, so it seemed like an ideal design for this situation. They claim that the directors add an extra 3dB of gain to the Moxon Rectangle design – about 9dBi which is more than a three element Yagi.

The antenna was quite expensive to buy. It is quite rugged and heavy but looks a bit home made. While the driven element and reflector made use of Jubilee clamps to tighten the main elements on to the smaller tubing used to form the corners, the directors used self tapping screws which had worked loose in transit (and probably would work loose in use due to wind vibration) and which stripped the inner hole when I tried to tighten them. You are left to your own devices to find a way to weather proof the feeder connection. Since my antenna is going to live a cosseted life away from the wind and rain I was not bothered by these issues.

The antenna presents a 50 ohm load but needs a balun to prevent feeder radiation. Vine Antennas offers a choke balun (apparently several turns of coaxial cable held in a loop using cable ties) for an extra £15. I decided to do without this, but I placed a clamp-on RFI ferrite over the cable close to the feed point which will hopefully achieve the same result.

The SWR is almost 1.0:1 at 144.0 MHz, as the plot from my AA-200 antenna analyzer shows, but it rises steeply to 1.4:1 at 144.4MHz and 2:1 at 144.8MHz. Clearly I had better not use this antenna to work satellites.

It’s a bit early to say how performance compares with my old Moxon Rectangle. The beam width does seem sharper and the front to back ratio seems quite noticeable. I heard the GB3VHF beacon for the first time since it moved to its new location, but it is in and out of the noise on slow fading as it always used to be. I can clearly hear the Northern Ireland beacon GB3NGI, which curiously is the same strength on the SuperMoxon as it is on the ribbon cable Slim Jim (which is also due for replacement with a commercial antenna.)

This antenna is probably as good as I am going to get given the restricted space available. The SuperMoxon design is copyright Vine Antennas and commercial reproduction is prohibited, which should be borne in mind if you try to make your own version.

• Swap one channel with another frequency due to federal licensee digital traffic which often on this channel
• Increase the power limit from 50 watts PEP to 100 watts PEP
• Allow CW, PSK31, and PACTOR-III modes

I just got round to checking the Sport Radio page of the May RadCom so as to transfer to my wall calendar the dates and details of any contests I might be interested in making some contacts in this month. I happened to notice that the exchange for the 144MHz Contest on 15/16 May is RS(T), serial number, grid locator and post code.

Post Code??? What’s the point of that? And what if you are operating portable from a hill somewhere and don’t have a post code? Daft idea if ever I saw one.

I’m not paranoid, but I think everyone is out to get me!

I ordered some connectors from eBay seller m0jpm and, because I have been thinking about getting a radio that has N type connectors on it, I decided to order a couple of BNC to N-type adapters so I could use the much easier to obtain BNC plugs on my antenna cables. The listing I ordered from is shown below.

The package arrived this morning and when I opened it, to my dismay I found that the adapters were the reverse of what I wanted. As you can see, they are for attaching N-type plugs to BNC sockets.

It has sometimes happened that I ordered the wrong thing by mistake, so I was relieved when I checked the eBay listing and saw that this time it was the seller’s mistake not mine. But my relief turned to anger when I emailed the seller to inform him of the error and received the reply: Dear g4ilo, Hi we have send you what you have ordered, as this is the only n-type to bnc we have listed. but if you not happy send it back for a refund.

Is it really necessary to insult my intelligence by telling me “we have send (sic) you what you have ordered”? I will send the adapters back for a refund (and no doubt be out of pocket for the postage) because they are no use to me. But I shan’t be buying anything from m0jpm again.

In a comment to my previous post Ricardo CT2GQV said that I should give up buying on the Internet. I wish I could, but if I did I would have to give up the hobby because it is not possible to buy radio stuff round here.

Welcome to Handiham World!

A new antenna goes up at Handiham headquarters

By Patrick Tice
[email protected]

As most of our regular readers and listeners know, the Handiham headquarters has moved from its long-time Golden Valley offices to a new location at Camp Courage near Maple Lake, Minnesota. We already had a vertical antenna at the new location, but we really felt that we needed a more versatile wire antenna that would be able to tune a variety of different frequencies. We settled on a 300 foot dipole fed with 450 ohm ladder line and a current balun. Coaxial cable from the balun takes the signal to the antenna tuner and to the TS-570 transceiver currently in place at our operating location.

As you can imagine, getting an antenna of that length up into the air can be quite a challenge. We had the advantage of some pretty tall trees from which we could support the antenna, and with some careful planning we were able to run the legs of the antenna out into some fairly clear spaces while still using these tall trees as supports.

Volunteers Dave Glas, W0OXB, and John Harvard, KC0UHY, had put up these “OXB Special” antennas before, so all I really had to do was follow directions and do as I was told. Dave directed the operation, as he is the real wire antenna expert. Not only had he ordered the materials and did some assembly ahead of time, he also procured the materials by getting the support of the Handiham affiliated Stillwater Amateur Radio Association, which paid for everything we needed. Dave also drove and brought the necessary tools. You could certainly tell that he had done this kind of antenna work many times before!

The weatherman cooperated on Tuesday, May 4. The sun was shining and the temperature was in the mid-70s. Although we had some wind, it wasn’t really more than a modest breeze and we were able to use the wind to our advantage in launching a tennis ball loaded with a couple of heavy lead sinkers as a lead for our fishing line. The tennis ball is launched using a slingshot like device that was donated to the Handiham program by volunteer and donor Bill Rouch, N6HBO. In order to get the tennis ball over some really tall trees, Dave cut a small slit in it and slipped in a couple of lead fishing weights. This gave the tennis ball enough mass to easily fly over the tallest branches. When all was said and done, the average height of this 300 foot antenna was probably close to 45 feet. That is really pretty good for an antenna of this length held up by trees.

We did some preliminary tests and then had to head back home to avoid getting stuck in rush-hour traffic. We will do some of the final work on the station later on when we receive the expected donation of an automatic antenna tuner from Eliot, KE0N. Do you see how volunteers, donors, and staff all work together to make a project like this possible? We are so grateful for everyone’s assistance. We couldn’t do it without you!

Eventually, we plan to use this new antenna on a second Internet remote base station. This will increase the operating capability by adding not only the second station but the ability to operate on the 160 m band and on the 6 m band. If this new antenna system works as well as expected, we may even consider upgrading the antenna system at the Courage North location, also adding 160 m and 6 m there.

Remote base operation will be an important part of our services in the years to come. Thank you for your support.

A few weeks ago I set up an experimental low power EchoLink node for use as a personal EchoLink “hot spot” using my FT-817 and a dummy load. I planned to make a a dedicated transceiver / computer interface for this. I thought I found the ideal basis for the project in this UHF Micro Transceiver Module from Elcom Research, a Greek company that makes packet radio and APRS products. The transceiver runs on 5V and can be powered by a computer USB port.

Perhaps I should have been warned off by the fact that an enquiry made through the web form on the Elcom site went unanswered, but I went ahead and ordered the module on 9th April, paying online using PayPal. After a couple of weeks nothing had been received, so I sent an email enquiry and received a reply that it had been sent by air mail and should be with me by the end of the week or the beginning of the next one. This was during the flying hiatus caused by the Icelandic volcano, so I gave it a bit longer. However it is now a week after the week that the module should have been received at the beginning of, and a further email received no answer at all. It looks unlikely that I will receive the module at all, so I guess my only option is to initiate the PayPal disputes procedure.

Ryan, K3SFG, asked us to pass this along to our readers:

CQ young hams…CQ young hams…

The Youth Net takes place every Saturday @ 2 pm (CA Time, PDST)

It is on the N6NFI Repeater, 145.230 -100. Young hams, 18 or younger, can also check-in through Echolink, using KR6DD-R (271122) or N6WN-R (477737).

Please help us get the word out, and if you have any questions, suggestion, etc., please contact K3SFG at [email protected].

Note: Only hams 18 and younger can check-in to this net. Unlicensed youth can check-in under the supervision of a control operator.

Please visit http://www.sbara.org/index.html and click on Youth Group in the left side bar.

Thanks and 73!

– Ryan, K3SFG