Ron, A few quibbles with your analysis. First, the antenna that I have described is a simple half wave dipole, fed at a current maxima. The only tricky part is the power rating of the choke that serves as the end insulator. My choke is NOT a matching element, it an end insulator!
Second, this antenna interacts with surrounding objects (including the earth) just as any dipole would if hung in the same position, NOT as a ground mounted vertical would. The major loss in a ground-mounted vertical is due to resistive losses due to return currents flowing in the lossy earth, which can be made very small by adding enough radials. In MY antenna, the return currents are entirely within the antenna. On Mon, 2 Mar 2009 14:20:33 -0800, Ron D'Eau Claire wrote: >The PAR End-Fedz (Par's spelling) is a Fuchs type antenna; an end fed 1/2 >wave radiator. >Its advantage over shorter radiators is that it requires very little ground, >if any, since it's fed at a voltage loop. Efficiency is not compromised by a >mediocre ground as is so common with radiators 1/4 wave or less in length >because virtually no current need flow into a ground system. >If it's mounted vertically it will still have the induced ground losses all >verticals have NO! Verticals have "ground losses" if the earth is what's carrying return current and terminating the field. In the antenna we're describing, the outside of the coax acts as the other half of the dipole, so it carries the return current and terminates the field! BUT -- for this antenna to work, the quarter-wave length of the feedline between the wire and the choke must be in the air (and the higher the better) -- that is, it is part of the antenna! This antenna can be vertical, horizontal, or sloping. It can even turn corners. If, for example, you were to toss it out the window of an upper floor and into a tree, it would act just like any other center fed dipole of the same length at the same height! Another point about "ground losses." The earth serves a second function with any antenna -- it acts as a reflector for the field that the antenna generates, and the interaction of the reflected field adds (algebraically) with the direct field to form the antenna's vertical pattern. The BEST that the reflection can do is add 6 dB at low angles. If the earth is lossy, the reflection is weaker, which makes the lower angle parts of the pattern weaker. 73, Jim Brown K9YC ______________________________________________________________ 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
