Why not feed all of dipoles as a phased array? Providing the direction you
want to point isn't off the end of the dipole, then that dipole can
contribute to the pattern. Sure, you won't be able to use some trivial
phasing like 90 degrees, but it might repay a bit of fiddling with any of a
number of antenna modeling programs just to see what might work. Programs
like 4nec2 can be set up with current sources and symbols for the relative
phases, then can do an optimizing for forward gain, or F/B, or nullling
interference, or whatever.
You'll want something like this at the end of your NEC deck( I've used 4nec2
syntax for the symbols). 901..904 are the feedpoints for the 4 antennas.:
SY P1=0 ' initial phases
SY P2= 100
SY P3= 200
SY P4= 300
EX 6 901 1 00 cos(P1) sin(P1)
EX 6 902 1 00 cos(P2) sin(P2)
EX 6 903 1 00 cos(P3) sin(P3)
EX 6 904 1 00 cos(P4) sin(P4)
Once you've figured out if you can get a pattern like you want, then, you
can look at the feedpoint impedances and design a set of LC networks to
generate just those phases. If you can decide on just a few dominant
directions (and the dipoles alone for other directions), then you don't need
many different networks.
----- Original Message -----
From: "Paul B. Peters, VE7AVV" <firstname.lastname@example.org>
To: "TowerTalk" <email@example.com>
Sent: Saturday, October 30, 2004 12:06 PM
Subject: [TowerTalk] Half-Square or ?? For 80m
I just had my tree climber back to the acreage and now have two new antenna
supports at 110 feet. The two trees are 130 feet apart. Given the lay of the
land, the new supports are on a north - south alignment -- not ideal, but I
can't find a method of rotating the land just yet.
I'm looking for suggestions on what might give a little additional gain over
the two existing dipoles I already have in place. The dipoles are at 110
feet and they are at right angles to one another -- so one for lp/sp and the
other for JA and NA.
I have been considering a half-square for the new space -- it will just fit
nicely with the horizontal 1/2 wave section at 123 feet for operation on
75m. As I continue to do my research, I wonder what other suggestions list
members might offer me. Thanks in advance for any and all suggestions.
73 de Paul, VE7AVV
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See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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