The radiation patten from a half wave antenna is the same whether it is end fed or center fed. An inverted vee is an inverted vee, regardless of whether you feed it at the center or the end. The same for a sloper.
Put up the wire and the feed where it works for you, sloper, horizontal, or vee; and end or center fed. wunder K6WRU CM87wj http://observer.wunderwood.org/ On Sep 22, 2014, at 9:29 PM, Vic Rosenthal <[email protected]> wrote: > I agree. I would just add that if you use an inverted L or V configuration, > be sure the included angle is 90 degrees or greater. Otherwise there will be > some cancellation of radiation from the two legs. As a thought experiment, > consider what would happen if you reduced the angle to 0. That would make the > antenna into a parallel line which wouldn't radiate at all. > > Vic, k2vco > >> On Sep 23, 2014, at 2:20 AM, Rick Dettinger <[email protected]> wrote: >> >> I have a similar antenna. >> I would use the inverted "V" or "L" configuration. You want the center of >> the antenna as high as possible. >> Mine is an inverted "L", but the far end actually is about 20 feet below the >> center, which is 50 feet high. The maximum radiation is where the current >> is greatest, a quarter wave from the far end, which has no current. Mine >> works quite well for a single wire. I made it a little more than a half >> wave at the lowest frequency, so I can use a remote tuner at the base for >> other bands. I feed it against a less than great radial system for all >> bands, but for a half wave, this might not be very important. The base is >> 140 feet from my shack, fed with coax in a conduit. I also have a 43 foot >> vertical, which I can select by remote switch. Except on 20 M, the >> inverted "L" usually works better. >> >> 73, >> Rick K7MW >> >> >> >> >> >>> On Sep 22, 2014, at 2:49 PM, <[email protected]> wrote: >>> >>> Hi All, >>> >>> Here's a question for the antenna gurus among the group. It's about the >>> best way to deploy an end fed half wave antenna. >>> >>> First of all, I assume most would say to put the entire antenna up in the >>> air as high as possible, and in a horizontal plane. I understand the >>> advantage of doing that. However, what about a situation where you only >>> have one support? My first inclination would be to deploy the antenna like >>> a sloper, with the far end at the top of the support, and the other end at, >>> or near, the rig. I started wondering, though, about where the maximum >>> radiation occurs. In a half wave antenna, the current max is more or less >>> in the center of the antenna. So, would it be better to get the center of >>> the antenna as high as possible (taking advantage of the one support you >>> might have), and then maybe bending the other half back downwards, sort of >>> in inverted vee fashion? That would be as opposed to just running the >>> antenna up in a straight line to the top of the support, thus possibly only >>> getting the center about half as high as the top of the support. >>> >>> Here's a more definitive description of what I am thinking about, and >>> compares to the situation I have. I have a pole that goes up approx. 40 >>> feet. If I deploy the EFHW in sloper fashion, with one end near the ground >>> close to the rig, the center of the antenna would only be at approx. 20 >>> feet. Also, On 40 meters (the band I would be using), the pole would need >>> to be some 50+ feet from the rig. Alternatively, what if I move the center >>> of the antenna up closer to the top of the pole, and have the rest of the >>> antenna slope back down to another tie point? Wouldn't this be apt to work >>> better, even though I have created something similar to an inverted vee? >>> >>> I know a couple of RVer's who do something similar. They have two poles in >>> use, one of which is much taller. They deploy their antenna so that the >>> mid point of the antenna is near the top of the tallest pole, then over to >>> another shorter pole, and then back down that 2nd pole vertically--almost a >>> somewhat slanted "U" shape. Their results seem to be decent, but I don't >>> know if there is a better way to do it. Their method condenses the lateral >>> space required to deploy the antenna, thus fitting within most RV sites. I >>> don't know exactly what this does to the impedance at the feed point, but >>> they use tuners to resolve any mismatch. The pole I have is somewhat >>> taller than either of the ones they use. >>> >>> Anyway, I assume I could do the sloper approach without creating any >>> serious issues, but I'm curious about what others think of the "vee" >>> approach to get the antenna center higher. >>> >>> I appreciate any suggestions. >>> >>> Dave W7AQK >>> >>> >>> ______________________________________________________________ >>> 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 >>> Message delivered to [email protected] >> >> ______________________________________________________________ >> 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 >> Message delivered to [email protected] > ______________________________________________________________ > 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 > Message delivered to [email protected] ______________________________________________________________ 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 Message delivered to [email protected]
