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[antennaware] Homebrew vertical construction

 To: [antennaware] Homebrew vertical construction gary@noblepub.com (Gary Breed) Wed, 23 Sep 1998 09:20:23 -0400
 ```Good to hear from you,. L.B., A few follow-up comments... ---------- a. In free space, where there are no reflections, the hat vertical has a larger length of high current than the 1/4 wl w/gp. Hence, for straight out (tangential) radiation, we would expect higher gain relative to the standard (dBi) than from the 1/4 wl w/gp. ----------- Correct ------------ b. Over ground, the hatted vertical has some interesting properties relative to the way in which you set up the project. Since the antenna feedpoints--1/4 wl down from the top--are the same, we should look at the radiation originating below that point. ------------ The most notable thing about the "bottom hat" is how rapidly it falls off in maximum gain, whether adding a small hat at the vertical dipole end of the experiment, or shortening the 1/4 wave radials at the other end. It's gain is always below a straight line between the START and END points. ------------ c. The sloped radial (type 1) antenna is quite interesting ------------ I also considered that the sloped radials slightly skewed the main lobe upwards, improving the summation with the reflected wave. ------------ d. If you were working with higher altitudes for the antennas, This would be important if someone replicates this experiment for 40 meters, for example. ------------ You're right -- a brief look at this scenario will convince anyone with that kind of available height to use a horizontal antenna. ----------- e. The maximum gain differential, although appearing very distinct, is still about 1/2 dB or less than 0.1 S-unit ------------ True, although the best-to-worst ratio is 1 dB, which might be statistically significant in, say, a contest situation. This difference would also be multiplied in an array, such as a four-square. ------------ f. Average ground is in fact one of the lowest gain grounds over which a vertical antenna system can be placed. ----------- Look at Georgia on your conductivity map! "Average" ground is better than I have under my antennas! ------------ g. I concur that more radials in the models are useful to try, although since you are using a wholly elevated system, You might make the increases modest for each replication. ------------ An increase from four to eight is probably sufficient to establish a trend. ----------- I hope something in these notes will be useful to you. ---------- Yep! 73, Gary K9AY -- FAQ on WWW: http://www.contesting.com/antennaware-faq.html Submissions: antennaware@contesting.com Administrative requests: antennaware-REQUEST@contesting.com Problems: owner-antennaware@contesting.com ```
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