Since I’ve owned my KX-1, the only two antennas that I’ve ever connected to it are the 40m dipole in my backyard and the 28-ft. wire (with three radials) described in the KX-1 manual. The 28-ft. wire is the only antenna I’ve ever used when operating portable.
While I’ve had good success with the wire, I knew I could do better, So, last night, at our club’s AMP Team meeting—where AMP stands for ARROW Mobile and Portable—I tried something new. I built a 67-ft. doublet from some 30-ga. wire I have and fed it with some twisted-pair wire. Theoretically, I figured that if I made the twisted pair a half-wavelength, then I’d have a relatively low impedance at the rig.
I cut the two elements, and then had a brain fart and cut the feedline to the same length. Now, theoretically, that should be bad, but I decided to hook it together and see what it would do.
I stripped the wires, and using a dogbone insulator as the center insulator, used wire nuts to connect the feedline to the antenna elements. At the end of the elements I just looped the wire and then tied a piece of string to the loop. Using a tennis ball on the other end of the string, I got the string over a branch and the wire up into the trees. The antenna was up only about ten feet, and I got some ribbing from one of my friends about it making a good NVIS antenna, but I pressed on anyway.
I connected the feedline to the binding posts on the BNC-binding post adapter, turned the KX-1 on and hit the antenna tuner control. Despite having only a quarter-wavelength of feedline, the tuner tuned it up just fine.
The real test was whether or not I could make any contacts. Tuning around a bit, I was very much encouraged. There were lots of signals, many of them S7 and above. Just for kicks, I called CQ around 7040, but when I didn’t get a response, I tuned around a bit.
Doing so, I nabbed Jozef, WB2MIC, in Wells, VT around 7058. He had a fine 599 signal, and he gave me a 559.
After a nice QSO, I tuned around some more and heard N5DY, Stillwater, OK calling CQ at 7036. He came right back to me, and although he wasn’t copying me as well as Jozef, we had a nice QSO. He was running a 4 W homebrew transmitter.
Finally, I worked Greg, AA8V, in Frostburg, MD. He gave me a 459 report.
All in all, I’d say my new antenna is a big success. Being made from 30-ga. wire, it’s very light and I got it up into the trees pretty easily. And it also turned out to be a good performer.
I’ll be trying it out again at the next AMP Team meeting. Next time, I’ll take my antenna analyzer along to actually measure the impedance.
Thanks for the post, I am just about ready to put up an 80 meter dipole, so thanks for the description, it sounds very interesting. Be sure to post the results you get when you try it out.
73, KI4WLR
http://www.ki4wlr.com
Hi Dan! Nice antenna idea. Your quarter-wave (instead of half-wave) feedline might be helping you out. The Z0 of the twisted pair is probably around 100 Ohms and the antenna feedpoint Z is probably 15-25 Ohms since it’s low to the ground, so your input Z at the end of the feedline might actually be sqrt(100*25)=50 Ohms! If you’ve got a big #43 (or similar mix) toroid around, you could also make a balun at the rig end by wrapping the twisted pair around the toroid several times before connecting to the binding post adapter. Have fun!
I hadn’t thought about it that way, but it’s’ an interesting idea. I will take my antenna analyzer and make some measusrements.
I do have toroids and will try the balun thing next time. I don’t think I’ll need such a big toroid, though, since the KX-1 only puts out 3.5 W.