Good to hear from you,. L.B.,
A few follow-up comments...
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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.
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Correct
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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.
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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.
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c. The sloped radial (type 1) antenna is quite interesting
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I also considered that the sloped radials slightly skewed the main
lobe upwards, improving the summation with the reflected wave.
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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.
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You're right -- a brief look at this scenario will convince anyone
with that kind of available height to use a horizontal antenna.
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e. The maximum gain differential, although appearing very distinct, is
still about 1/2 dB or less than 0.1 S-unit
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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.
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f. Average ground is in fact one of the lowest gain grounds over which a
vertical antenna system can be placed.
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Look at Georgia on your conductivity map! "Average" ground is
better than I have under my antennas!
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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.
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An increase from four to eight is probably sufficient to establish
a trend.
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I hope something in these notes will be useful to you.
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Yep!
73, Gary K9AY
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