Have you ever thought of using the tower & antennas as a shunt-fed
vertical? A vertical antenna does not have to be a quarterwave long to be
effective, it can be longer, but not electrically longer than 5/8
wavelength.
Shunt feeding is like a gamma match at the tower.
The antennas on your tower will load the tower as a vertical on 160. I
wouldn't think it would be much longer than quarterwave, though. Be a good
exercise for computer modeling.
The trick with all this is to forget about a 1:1 VSWR, and think of the
tower as an impedance that you will have to match to the transmission line.
Jim, W1EQO
Original Message:
-----------------
From: Dick Green WC1M wc1m@msn.com
Date: Wed, 17 Oct 2007 00:50:12 -0400
To: towertalk@contesting.com, yccc@yccc.org
Subject: [YCCC] interaction from low-band wires
Hi,
I'd like to hang a trapped 160/80 inverted vee off my 110' tower as a
temporary solution for the low bands this year. The tower is on a steep hill
and too far from trees for a dipole to be feasible, so it'll have to be an
inverted vee. I have a 40-2CD at the top of the tower, and a 3-stack of 4-el
SteppIRs on Tic rings at 96'/64'/34'. The 14' spacing between the 40-2CD and
top SteppIR make it impossible to hang the vee above the top SteppIR and get
enough clearance for the yagi to turn. I'd like to hang the vee right under
the top SteppIR, say at 94 feet, to get it as high as possible, but I'm
concerned about interaction between the vee and yagi. After all, I went
through a lot of trouble and cost to put Phillystran guys on this tower to
avoid interaction!
Is it likely the vee will interact with the yagi? Would it be better to hang
the vee at 85 feet and put some separation between it and the top SteppIR?
Also, does it matter how far from the tower I hang the vee?
73, Dick WC1M
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