SM0DTK'S 20 Meter Corner Fed Vertical Moxon
Vertical Moxon with different feeding.
Anyone who has tried vertrical dipoles and vertical Moxon antennas knows that the impedans at the feeding point changes depending on the position of the used coax cable. To have a good match between the 50 ohm coax and the antenna the coax has to run at least 45 degrees out from the fed element. Best is 90 degrees. Otherwise the matching will not be good and SWR will rise rapidly. In high winds you will note this if your coax is not well fixed.
To avoid mentioned problem with matching I have tried another way to feed a vertical Moxon. I opened up the lower corner of the fed element and used a transformer to match 50 ohm to the new feeding point. It works fine and it is really much easier to install this application compared with a conventional fed Moxon.
This is the setup:
Here's the balun.
and here shown in the operating position.
Martin can be reached at: sm0dtk (at sign) passagen.se, or through his excellent website at http://hem.passagen.se/sm0dtk/. Martin has many antenna designs which are clearly shown and easy to build. His site is highly recommended for hams looking for some good summer projects.
Steve Hammer, K6SGH