SM0DTK'S 20 Meter End Fed Vertical Moxon
Endfed vertical Moxon for 20 meters. With this one I worked FO/F6CTJ in the Marquesas!
There are some reasons why you should endfeed your vertical Moxon antenna. You donīt need a hanging coaxcable from your radiator. You get an antenna with less windbreak and an antenna in good balance. You just need to voltage-feed the radiator with a simple LC parallel resonant circuit like you feed a Bob Tail antenna or a Half Square antenna. I have used an Amidon T200 core with 21 turns 1 mm enamelled cu-wire to get an inductance of 6.46 microHenry. Coax from the transmitter is connected to a 4 turns link of 1 mm insulated cu-wire. With a piece (26 cm) of RG8 coax cable the LC circuit resonance on 14.12 MHz. You can of course use an capacitor of about 25 pF instead of the piece of coax. Remember that it is high voltage when loading at the end of an antenna (high impedance).
This is how the antenna is constructed:
The hub is an old beachtennis racket:
73, SM0DTK, Martin Download this page as Word for Windows file.
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.
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Steve Hammer, K6SGH