You are likely to get a lot of ideas and comments, but a bit of study will substantiate what I am about to say on the subject - it is all just practical physics, no real 'magic' involved. (OK -- some theory from EE Field Mechanics theory is involved too).
If you mount the 43 ft. vertical on the roof and run a heavy gauge wire from the roof to the ground, the length of the vertical will be increased by the length of the wire. I don't know whether that is good or bad - it all depends. For low band use, the extra length can be a good thing, but the take-off angle on the higher bands will not be as expected (and published) for a 43 ft. radiator - it will begin to break up into higher angled lobes. At what frequency that occurs depends on th length of the added wire. If what you want is the 43 foot vertical, then buy enough telescoping tubing (DX Engineering is one source) to make the total of your "wire from the housetop" plus the vertical radiator equal to 43 feet (not critical since it must be tuned anyway). Then you can bury the radials in the yard. How efficient it will be depends on the number of radials. The other approach is to put the 43 foot vertical on the rooftop and use 4 43 foot radials at its base (yes, 4 wires on the rooftop) - they can droop down the corners of the house if there is no other choice - use insulators as if the radials were antenna wires (they actually are). These radials should NOT be connected to ground, but are a part of the antenna. You can feed the antenna (and radials) with open wire or ladder line and use a tuner in the shack. You should have good performance on 40 through 10 meters with a low angle of radiation (good for DX). The horizontal component of radiation will cancel if the radial pairs are oriented symmetrically (180 degrees apart). In fact, you might be able to get away with two radials rather than 4, but 4 will be slightly better. Again, these are elevated radials and are a part of the antenna system - do not connect them to an earth ground. You should achieve a low angle of radiation on 80 through 20 meters, but the lobes of maximum radiation will be higher above 20 meters. That is characteristic of the popular 43 foot vertical. 73, Don W3FPR djmd wrote: > Hello, > > Currently without any HF antenna and after seeing my friend's success with > his homebuilt vertical, I'm starting to consider a self-supported 43' > allbander, from DX-Engineering or the like. Not really looking to discuss > general performance vs. other antennas, but I am curious about my options > for installing. > > I live in a very standard subdivision-type lot, about 180'x70' with a > single-story 55'x25' house right in the middle. The one option that I have > to rule out is putting the antenna smack-dab in the center of the backyard. > Besides just not wanting an antenna in the middle of my backyard, that would > put the antenna way too close to the 7200v powerline strung over my property > line. About the only ground-mounted option would be 5-10' away away from the > back of the house, which would make it clear the high-power line, but it > could still come in contact with my 240v residental feed if it went over in > that direction. > > My ideal location would be on the roof. Not only could I be 100% clear of > any powerlines, phone, or cable, but it would be nearly 20' higher, and > basically in the clear of anything to the sides. My question, therefore, is > what about radials? Draping radials across the roof doesn't sound like an > option to me, mainly for asthetic reasons. So I ask: could I send #2 or #4 > copper from the antenna base to both the front and the backyard, and connect > it each one to radials in both the front and back yard? I would be mounting > this antenna within 10' of the end of the house, so I could send 1 piece of > copper down one of the ends of the house, and then split off from there in > each direction. It would probably then take about another 20-30' in each > direction before it met with the radial distribution point. > > Thank you for any insight. Will probably post this to eham verbatim as well, > but wanted to start here. > > K8DJW > > ______________________________________________________________ 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
