On 11/18/2017 1:34 PM, JT Croteau wrote:
Friends, what would be a good end fed wire setup that will match well
with the internal KX3 ATU and cover, hopefully, 80, 40, and 30 meters?
I went out to my winter camp site, with two really tall pine trees,
and tried to experiment with a 9:1 UNUN, 135' radiator, and 35' of
RG8X.
The ARRL Handbook and ARRL Antenna Book are your friend. If you don't
own them, RUN to your computer and buy one, new or used.
The short answer to your question is that, in general, end-fed wires
need a counterpoise to work well. For your situation, I'd build two
end-fed center-fed dipoles, one for 80 and one for 40, launch one into
one of the trees, the second into the other tree. 75 ohm coax is the
best match to these antennas, but 50 ohm coax will work. The following
slide show describes this technique, beginning on slide #70.
http://k9yc.com/VerticalHeight.pdf
If possible, rig your dipoles so that they slope away from the tree(s)
in which they are mounted. Anecdotal reports, and my limited experience,
say that trees absorb a bit of the RF from a wire very close to their
trunk. I suggest that you pull both antennas up as high as practical.
If for some reason you don't want to rig a dipole like this, pull a
quarter wave wire for both bands into those trees and rig a quarter-wave
counterpoise for each that's at least 6-8 ft above ground. If a feedline
is needed, use RG8X with a good common mode choke but no transformer.
73, Jim K9YC
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