Re: KAT2 with EFHW antenna

Posted by Mercury on Aug 24, 2011; 1:54pm
URL: http://elecraft.85.s1.nabble.com/K3-S-meter-oddities-tp6676870p6720262.html

Steve Yates, AA5TB, has a very informative web page on EFHW antennas and how to build a parallel tuned circuit with a link coupled feed at the radio end to reduce the 1800 to 5000 ohm impedance to a 50 ohm non-reactive load. He has examples of both QRP and QRO versions of the circuit. I built the QRP version which uses a polyvaricon capacitor (available through Hendrix Kits among other sources) to create a very small tuning device that will match resonant End Fed half wavelength antennas on 40m, 30m, 20m, and 17m. I use it mostly with a 33 foot wire on 20m raised on a 31 foot Jackite fiberglass pole and have had fun working DX with 5 watts. It is easy to change bands by exchanging the wire with one cut for the band of interest. I do not use a counterpoise and do not have any trouble at the rig. Steve explains why this works. For higher power a one meter counterpoise helps. I use this antenna with a K1 and K2, both with internal antenna tuners. The tuners are not needed, but I
  leave them activated to easily compensate for any small mismatch across the band.

Steve's page is found at http://aa5tb.com/efha.html

William Ravenel, AI4VE
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