Gene, KC0RXY wrote: I'm needing to install an antenna in my new home. An attic loop is a necessity ... can't run an outside wire easily.
I'm assuming that an 88-ft loop will be non-resonant in all bands 80-10, and fed with ladder line to the tuner should work. Other suggestions? ---------------------------------------- For a number of years I was an apartment dweller who only once had permission to run an outdoor antenna. My antenna of choice in each situation was a doublet using whatever length I could manage. The feeder was open wire line made up of two small white wires (since apartment walls are invariably white) that went straight from the ATU on the operating table up the wall (held to it with a couple of small staples), through two small holes in the ceiling where it meets the wall and up to the center of the doublet. Once above the wall, a couple of lightweight insulators made from bits of scrap plastic (cut from film cans) were used as spacers. The spacing is not critical. It worked very well on all bands where I could get at least 1/4 wavelength of wire up into the attic. That is, with about 35 feet of wire (17 feet each side of the feeder) hung in the attic just under the roof so it was sort of inverted V, I could work on all bands 40 meters and up. The loss of efficiency of a short doublet doesn't really show up until the radiator gets to 1/4 wavelength or below. Of course, it would also load on 80 and even radiate. Shoot, an 8-foot mobile whip will radiate on 80. But I never seriously tried to operate on 80 (or 160) from an indoor antenna because of the electrical noise. Lamp dimmers, blow-dryer motors, every sort of appliance seems to be designed to emit maximum electrical noise on 80 and 160 meters! Only one time did I find my performance rather disappointing from such an attic antenna, considering its low height (usually about 20 feet since I was usually in a two-story building). It worked okay on 40 meters but performance on 20 meters and up was dismal compared to other QTH's. The roof was tile. Up close it appeared to be a colored concrete with a lot of air in it, so while the tiles were waterproof, they weren't as dense and heavy as normal tile or concrete. I found a broken piece in the garden, evidently left by someone who had done some repairs on the roof. On a hunch I took the piece of roofing tile into the house and put it in my microwave oven (with a glass of water to protect the magnetron). After a short run the water was warm and the piece of roofing tile was blistering hot! Minerals or something in the tile mix was definitely not "transparent" to radio waves - and its ability to soak up RF probably went up with frequency. So the sort of roof you have really does matter! The open wire feedline made of white wires attached to a white wall was virtually invisible - a nice feature since I often had my operating desk in the living room. Friends visiting would have to be shown the "feeder" before they'd see it on the wall from a few feet away. Ron AC7AC _______________________________________________ Elecraft mailing list Post to: [email protected] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
