I am going to be hanging an array of three 80M vertical dipoles from my new
tower, similar in concept to the description Tim Duffy K3LR, et al
published in the ARRL Antenna Compendium, Vol. IV. Mine will be three
dipoles spaced 120 degrees apart (equally spaced between the guy wires),
pulled out from the top of the tower at approximately 45 degrees and with
the lower leg of the dipoles pulled back in to the base of the tower (the
old inverted Vee on end). One dipole fed at a time, with the other two
serving as reflectors -- accomplished by floating rather than grounding the
two "reflectors" and 153 electrical degrees of feedline to each.
Right now I'm in the process of building a relay box to do the switching.
At this point it would be easy to incorporate another relay to switch
additional loading in and out of the circuit to enable the antenna to play
at both ends of the 80M band. But I am a little fuzzy on how best to
accomplish this. I think I want to tune the system "as is" to the lower end
of the band (Pete Smith's recent comments indicate the antenna is more
forgiving above resonance than below) and then switch in some reactance to
the driven element to make it appear electrically shorter than it is.
Should I just leave the reflectors and their feedlines alone and let them
appear to be longer and longer electrically as I tune higher and higher in
the band, or would it be worth the additional complexity to attempt to
switch reactance in to them too? I forsee THAT getting VERY complicated. I
would assume normally that I'd need capacitive reactance for the driven
element to make it appear shorter, but inserting it at the end of a 153
degree long feedline has me confused. I'd rather someone teach me how to
figure this out, rather than just giving me the answer, but I have to admit
I am having heavy going in the ARRL Antenna Handbook. Any hints greatly
appreciated.
On a separate but related note, I tried following the URL posted several
months back to the CATV home-brew connector page published in TowerTalk
awhile back, but the page is "Not Found" anymore at
http://www.tiac.com/users/kb1so/catv/.
I have several miles of 1/2" and 3/4" CATV given to me after a local
windstorm ripped through Libby this summer and I'd like to dope out how to
economically make some connectors for it.
Thanks all of your time and assistance.
Steve Zettel KJ7CH
near Libby, MT USA
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