I've studied this a bit, and about a year ago turned it into an
applications note, and then a presentation at several hamfests.
The app note is
http://audiosystemsgroup.com/ComparingVerticalsandDipoles.pdf
The power point slides for the presentation are in
http://audiosystemsgroup.com/LimitedSpaceAntennasPPT.pdf
As others have noted, there are many variables, all related to the
vertical angle that you're trying to work (changes with band
conditions), the efficiency of the antenna (usually radials, but
also losses to, and distortion of the pattern by, surrounding
objects), and the height of the beam.
My conclusion -- a dipole at a "good" height will nearly always
beat a vertical unless it's a VERY GOOD vertical, and a beam is 3-
8dB better than a dipole, depending on its size and design. I live
in a forest, where dipoles and verticals are easy but a beam is
difficult. I've tried very good verticals on 160, 80, and 40M, and
the 160 vertical is the only one that is as good as the dipoles
(and it's better than my 160 dipole, which is up 100 ft). That 160
vertical is 86 ft of #10 copper, with another 100 ft of horizontal
#10 copper as top-loading, and has 70 radials under it.
Bottom line -- if you can put up a decent beam for 20-10, by all
means do it. If you can't, try dipoles next. Verticals should
usually be the LAST RESORT. Exceptions -- vertical arrays, like 4-
squares, etc. But even then, a high dipole is likely to work as
well. For a lot more, see the pdf links.
73,
Jim Brown K9YC
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