Being away from home quite often and being the owner of Elecraft KX3 I often missed the opportunity to work /M. So I came up with an idea to build an antenna, a quick antenna to set up in any place. No need to look for trees, no slings, no fishing rods - at any parking lot. In a one (almost) word - car whip on steroids - to be placed quickly anywhere and anytime ;). So something like this was created.
I originally planned the height to be about 4-5m, which would allow the antenna to be tuned with a antenna tuner from 20m up, and no need for guy wires (this will only be confirmed in windy conditions somewhere on the hills). However, the match was not satisfactory. I decided to try - before using the tuner - to use a solution similar to MFJ931 ("tuning" radials - car body). Before using it, I decided to try to place a coil in series between the body and the "cold output" (coax braid) of the balun.
That was it! It turns out that the coil I made (about 45uH) can easily tune the antenna even on 80m. On 40m the work is possible without retuning in the whole band (you can fix match a bit with the tuner, but this is not necessary at all). How exactly this antenna works - it's hard to say for sure. It is definitely not a typical GP.
In a typical GP antennas the radiator is lenghtened electrically - here the radiator is without any coils. Looking at the impedance of about 70-ish Ohms it looks more like a vertical dipole (and since it is a very asymmetrical antenna it looks a bit like a length-tuned /by lengthening coil/ OCFD antenna - Off Center Fed Dipole). One arm is the vertical part, the lower arm of the dipole is the coil with wire ending in... a car body, which is a large final capacitance ("bottom hat" instead of "top hat" used in some constructions)... standing on rubber insulators in the form of wheels.
That's my guess, anyway.
Reports on pskreporter show clearly that the antenna certainly works and is quite good. The results below are on a "bare" KX3 and 15W to the antenna.
Do you have any thoughts on this antenna? Leave a comment!