SM0DTK's 40 meter Moxon
Wire MOXON for 40 meters
During summer days, I stay in my summerhouse in Gotland Island (EU-020) east of Sweden in the Baltic sea. A wonderful place not only for recreation but also for working HAM radio. No man-made QRM makes it easy to copy weak DX on higher bands, but on lower bands there are some problems with strong signals from Europe.
In morning hours we have pretty good conditions on 40 meters to the Caribbean sea in western direction but as mentioned some problems with QRM from strong east European stations.
On my lot I have some pretty high trees (15 meters) which can carry wire antennas. So what antenna to hang up to get some gain to the west and to reduce signals from the east? My choice was to try a moxon wire antenna made by very thin wire to reduce weight. I started up the Moxon Rectangle Generator and calculated the dimension for the antenna. Then I cut the wire according to the result from the generator and made some supports for the corners and for the feeding point by plexiglass.
Now comes the tricky part of the installation. How to get the supporting lines up in the trees? I used an aluminium tube joined with a glass fibre rod and was able to get the bearing points up about 14 meters in four suitable trees for my project. I spent some time to get the right shape of the rectangle by adjusting the length of the four supporting lines.
Now it was time to connect the coax to the transceiver and measure the SWR. Sometimes fate is overwhelming so in this case SWR was perfect and I could use my 100 watts directly without any tuner. I used a long-wire antenna (60 m) and a full size GP for 40 meters to compare signal strengths with my new antenna. My expectations on my Moxon came true. I got my gain to the west and the QRM from the east was much lower. I easily worked DX in the Caribbean using 100 watts and I even thought that the morning sun was shining brighter. You can find more info on antennas, also a Moxon for 20 meters, at my website http://hem.passagen.se/sm0dtk
--73, Martin, SM0DTK
ed: Martin has a wonderful website and a large antenna section with many designs and construction details. It's well worth the visit!
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