Don gave you excellent advice. Keep in mind that you can "hear" with a mis-matched antenna far better than you can transmit. Indeed, a random length of wire stuck in the antenna jack will make an good receive antenna as long as the antenna isn't close to sources of RF noise (like computers and other electric/electronic stuff we have in our homes these days
Attic antennas aren't as good as an outdoor antenna, but I've used them running QRP at two QTHs with satisfying results. Mine were in an attic above the second floor - 66 feet long and fed at the center with "open wire line" made up from two small white hookup wires that came down through two small holes in the ceiling about 2" apart right above the wall and my operating desk, and were stapled directly to the drywall down to the tuner. They were virtually invisible unless they were pointed out. At one QTH where the roof and siding were wood it worked great, but at the second it was rather mediocre by comparison, although I still worked all over the USA on 40/30/20 meters and plenty of short skip on 80. I finally traced it to the concrete tile roofing material. Found a chunk and put it in my microwave and it got smoking hot in a minute (alongside a glass of water to protect the Maggie). That was a strong indication it was not very "transparent" at RF, and the attenuation likely went up with the frequency. But, in any case, getting RF to the radiating wire efficiently is paramount. That's why Don asked about your feed point. A 1/2 wave antenna (66 feet on 40 meters) will offer a pretty good match to 50 ohm line and even a workable match on 15 meters but on any other band it'll show a very high SWR that will cost you much of your RF before it even gets to the radiator. Open wire line, having a higher impedance (typically a few hundred ohms) will show a much lower SWR and so much lower losses. You can use a balun at the rig or simply connect one side to the center pin on the coax connector and the other side of the feeder to the ground lug on the rig. If the rig seems 'hot' with RF (tuning changes when you touch the rig, etc.) a balun will offer more isolation. If you opt for traps, you'll need to adjust things for lowest SWR on the feeder on each band. It's fussier to set up and you're limited only to those bands where the antenna shows a low SWR, but it allows you to use coaxial line efficiently. If you're in a single story building, you'll find low band operation is not as good because the antenna isn't high enough. But even at 15 feet above the ground, you'll put out a fairly good short-skip signal (your main lobe will be straight up). In almost any environment you'll make contacts with an attic antenna. Then it's a matter of thinking about how to make it better. If you need to bend the antenna to fit the attic, put the bends out near the ends, keeping the center section as straight as possible. It doesn't matter whether your antenna is indoors or outdoors: every Ham who tinkers with antennas wonders what might be changed to make it better, whether it's a simple wire or huge beam on top of a 90 foot tower. Ron AC7AC -----Original Message----- Looking for some advice. I am a new ham running a K3/10 with 66 feet of stranded copper in the attic using RG213 as a feedline. Using Fldigi, I hear and de-code CW, PSK, Olivia and Hell very well and from all over the world. When I call CQ I see it on the waterfall, hear sidetone and see 4 ALC bars on the K3.............but never an answer. Is it because I am using 5 watts from an attic location or maybe antenna problems? I don't believe it is the DATA A issue since I downloaded the most recent version of the K3 software. Any ideas? Thanks. -- Frank KD8FIP ______________________________________________________________ ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
