Ken,K0PP wrote: Copper-clad steel wire (Copperweld)...Proper insulators have lead-lined holes to "cushion" the wire.
A couple of things to keep in mind ... RF flows on/near the surface of a conductor, and the correct length of an antenna made from insulated wire will be slightly different than the formula-calculated length. --------------------- Good points, Ken although lead-lined insulators are going to be hard to come by soon, Hi! Also, the formulas are, at best, approximations. Not only can insulation affect the length, but so does the earth itself (unless it's many wavelengths away) buildings, trees, support poles, etc. The popular formula for 1/2 wave, 468/f(MHz) is only an approximation trying to account for typical end loading caused by capacitance between the ends and support wires through the insulators. A 1/2 wave in "free space" is closer to 492/f(MHz). The bad news is that unless one has non-metallic supports a few hundred feet high and in the clear, the formulas are only going to be an approximation of the right length to be self-resonant. The good news is that it's not important to be self-resonant. The biggest problem with a non-resonant antenna has little to do with the antenna itself. The problem is mostly the rig. Our modern rigs (including the Elecraft rigs) have fixed-tuned output networks. They only work efficiently into a load close to 50 ohms, non reactive, where the old rigs with tuning controls that had to be adjusted as one moved around in frequency worked very efficiently into a large range of impedances. Unfortunately, those tunable output circuits we used in years past don't provide the amount of harmonic rejection now required of our rigs, so you aren't likely to find any new designs using them above QRP levels. So the problem is to match the antenna to the fixed-tuned output network in our rig. Finding the magic length of an antenna is one way, but it's seldom good for much more than one band, and often not even for a whole band. So we use an antenna tuner to match the antenna to the rig. Now we don't care so much about whether we have exactly the right length radiator. Until the SWR gets up fairly high where feeder losses become a concern, it's a non-issue. And the ATU suppresses harmonics and other spurs even more. Ron AC7AC _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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
