A loop in the attic is asking for coupling to all those nearby conductors. They will do the following:
1) Capture and dissipate your precious RF. No-one will hear you. 2) Couple large amounts of electrical noise into your receiver. You will hear nobody. 3) Pick up even QRP levels of RF and funnel it into electronic devices in your house. The best choice is to put up a balanced 'doublet' or dipole outside. It won't be more expensive than a loop in the attic. If you MUST put it in the attic, I still recommend a doublet. It will couple to the wires, etc. but not as badly as a loop, which may exhibit magnetic coupling to nearby loops of wire. My guess is that lightning is as likely to hit a wire in the attic as one just above it but outside! But the more likely problem with lightning is damage to the radio from voltages induced from nearby strokes. You should make sure to have an arrangement to dissipate static charges on whatever antenna you choose, indoor or outdoor. On 4/11/2011 4:11 PM, Wayne Conrad wrote: > My radio (K2 with the internal ATU) hasn't shipped yet, but that > shouldn't stop me from putting up an antenna, right? If only I knew > what to put up, that is. That's where I'm asking for help. > > I want to start out with an loop antenna in the attic. Why loop? Mostly > the very American idea that more wire must be better, plus it's > balanced--I hope to not need a separate RF ground, or counterpoises, or > any of that jazz). Why the attic? So I don't have to worry about > lightning protection, and because it ought to be incredibly cheap to put > up. I've spent every dime I have on the radio, you see. > > The house is the usual ~60' x ~30 feet and "L" shaped, single story, and > the major axis is North/South. The attic is full of trusses and > fiberglass, but I can get to most of it, sometimes slithering on my > belly like a snake. There are the usual electrical wires, network > cabling (OK, maybe not everyone has CAT6 in their attic), TV coax, and > AC ducts going hither and thither. My shingles are asphault. > > I have no idea what band or bands I'll be on. I don't even have my > license yet. > > My thought is that I run the loop around the perimeter of the attic, as > close to the eaves as possible. Over the radio bench, I'll punch a hole > in the ceiling and drop feedline down the wall. > > I was thinking of open-wire feeder, because I "read on the internet" > that it might be better for this application. > > It occurs to me that I could omit the 4' of feedline and just drop the > two wires down. Using the self-adhesive conduit that the hardware store > sells, I could keep those two wires at "an appropriate distance" from > each other, and white conduit looks better against a white wall than a > black cable. I don't know if that's a good idea, or what "an > appropriate distance" would be. > > I don't know if I need a balun, or even what kind. > > I don't know whether I need to keep the antenna wire off of the rafters > with insulators, or can I just let it lay there. Nor do I know if the > answer to that question changes if I eventually go QRO. > > I don't know if the length of the loop matters. > > As you can tell, the ratio of things I know to things I don't know is > pretty small. Can you please help me improve that ratio? > > Thanks, and best regards, > Wayne Conrad > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:Elecraft@mailman.qth.net > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html -- Vic, K2VCO Fresno CA http://www.qsl.net/k2vco/ ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
