Posted by
David Gilbert on
Oct 10, 2019; 6:57pm
URL: http://elecraft.85.s1.nabble.com/KX2-Antenna-Curiosity-tp7655612p7655617.html
Your field antenna is essentially a very low off-center fed sloped
dipole slightly longer than a half wavelength. I'm not surprised you
can tune it with the KX2, but it certainly isn't any kind of ideal
antenna configuration that Elecraft would design for. They just made a
very well performing tuner for the KX2 that will work with almost
anything. I have a KX2 ... it's amazing what it can tune.
You didn't say how long your feedline is, but with a feed that far off
center the shield of your coax is probably doing some of the radiating
anyway.
Yes, a center fed normal dipole with the middle (high current portion)
higher off the ground (say 50 feet for 40m) and a common mode choke at
the feedpoint would almost assuredly perform better. If you can't get it
that high, a vertical (even a 30 foot wire oriented mostly straight up)
fed against a decent radial system might be a better choice if you don't
have a lot of surrounding buildings/trees/telephone poles.
For the record, I also have on rare occasions used low sloped wires fed
near one end against some sort of ground or counterpoise when camping or
for a hurried Field Day setup. They are easy to set up and sort of
work, but they always performed very poorly compared to even the most
basic dipole if I could get the dipole off the ground approaching a half
wavelength in height. Over the years I have operated roughly 20 Field
Day contests (almost always 5 watts CW for the extra QRP points) and one
year I used only a low sloped wire similar to what you described. It
was memorable for being the worst Field Day result I have ever had, and
that's in spite of the fact that I've placed top 3 nationwide in my
category on more than one occasion using only wire antennas strung from
tall trees.
73,
Dave AB7E
On 10/10/2019 9:01 AM, Joseph Shuman via Elecraft wrote:
> I have had my KX2 with the ATU for about 10 months and operate on 40m QRP SSB from various locations. Experimenting with different antennas I have experienced best results with a 58.5’ wire tossed about 25’ up a tree with a 16.5’ counterpoise. I ran the same length wire from my house to the workshop, grounded the shield side of the cable, and have seen similar results to the field setup.
>
> Is there some engineering/design factor of the KX2 for this type of antenna setup? I am planning to setup a Dipole at home, but as a newbie am wondering if the “ideal” Ham Dipole can be expected to improve performance.
>
> Keeping Watch-
> shu
>
> Joe Shuman
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