Now that we are pretty well situated in our new house, I decided it was time to give some serious consideration to what I was going to do in the HF antenna department. Given my reading of the CC&Rs, a full-on 135-foot dipole just wasn’t going to be in the cards, no matter how much I wanted it. But, we must all walk before we can run, so I decided that I would just be happy with something that was up higher than 10 feet in the air and would snag me a few QSOs without too much grief.
Just before we moved, I put together a fairly nice version of the Cobra Jr. (Jr). using 450 Ω window line with 14 AWG stranded wire threaded in the middle of the insulation to provide a 36-foot three-conductor linear loaded dipole. I got a small piece of Lexan to use for the end and center insulators, which also worked quite nicely. The plan was to deploy this antenna in the attic, but as the saying goes, no plan survives contact with the enemy. When I first poked my head up in the attic, I realized that I did not have the stomach to do the dirty work required to hang the antenna. The height of the attic at the apex is only about 4 feet and the “floor” is covered in about 4 inches of that old-style spray-in insulation. I’d have to get a jumpsuit and respirator in order to crawl around up there, all the while trying very hard not to let my large body fall through the ceiling. Umm, thanks but no thanks. I guess the Cobra just going to have to wait for another opportunity.
A bit more meditation on the subject made me realize that perhaps a random wire wasn’t such a bad idea. A new plan began to take shape in my brain. The shack is at the rear-center of the house. A large tree is in the back corner of the backyard about 30 feet from the shack window. A wire could be run from the shack up to one of the tree limbs without being visible at all from the front of the house. My immediate neighbors could see it in the backyard, but I don’t think it would be very offensive. So the new antenna is 70-some feet of 26 AWG stranded teflon-coated wire run from an access hole in the exterior shack wall, routed up the wall by some plastic wire staples, and up to a high tree limb. This would be worked against earth ground, provided by a short, direct wire connection to the 8-foot ground stake that I just killed my hands driving into the ground.
The big problem was figuring out how I was going to deploy the antenna. The house is in a subdivision with your standard mid-sized city lots. A few neighbor’s houses are pretty near the tree, and I could easily see an errant lead weight flying through the tree limbs and into a nearby window. Fortunately, I remembered that somewhere I had a leather throwbag and 75 feet of slickline stored away. A bit of digging turned up these two gems, and gave me hope that I could pull this off. I fashioned an end insulator out of a small piece of the Lexan (1″ x 2″) that I cut out with the jigsaw. One end of the random wire was tied off to one end of the insulator. 50 feet of poly/dacron rope was tied to the other end of the insulator, then the slickline was tied to the free end of the rope. After about 10 tries, I got the throwbag over a high limb and back down to the ground. After getting the feedpoint end of the wire into the shack and attached to the tuner, the length of the antenna wire turned out to be just about perfect. Only a little bit of the wire was doubled back over the limb towards the ground.
So how’s the performance? On transmit, the antenna seems to load up just fine on every band from 80 to 10 meters, with the exception of 12 meters. A bit of trimming will probably correct that. The receive side is a different story for a different post. I haven’t made any QSOs with it yet, but I suspect that will be remedied by this weekend. Now excuse me while I go sacrifice a few chickens to the Antenna Gods…
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[…] 2008 in Antennas, Operating Sit down, and let me tell you a tale of woe. As I mentioned in my last post, I got my random wire antenna up in the air and it seemed to tune reasonably well with my […]