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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