I am going to step in & out of this thread many times only because of my
experiences/work at/on phased vertical arrays.
Who and more importantly WHY was the decision made that the phasing must be
done at the antennas.?.?.?. You can do the phasing in the shack and not have
to run a voltage to the antennas and also isolate the stray R.F. path back
into the shack.
Why not run 2 equal lengths of coax from the antennas back into the shack,
preferably not in a length of 1/4 wave multiples. (Wavelengths are
calculated with velocity factor in all phased arrays)
Just my -2cents worth
MAL
N7MAL
BULLHEAD CITY, AZ
http://www.n7mal.com
Everyone in the world is
entitled to be burdened
by my opinion
----- Original Message -----
From: Dick Williams
To: towertalk@contesting.com
Sent: Tuesday, March 10, 2009 2:32
Subject: Re: [TowerTalk] phasing multiband verticals
Jamie,
I have two Force 12 160 mtr verticals that I have spaced at 1/2 wave and am
using the ComTek PVS-2 system. It uses a three wire configuration to switch
three directions. Before I bought that, I was using a home brew phasing
system that gave me either an end fire or cross fire pattern (feeding in
phase or 180 out). The nice thing about the ComTek is it uses a 2.25:1 UNUN
for the in phase matching and an electric 90 degree phase shift to give gain
for either direction of the end fire.
Actually the best spacing for their system on 40M is 49 ft (more than a
quarter but less than a half). I use 1/2 because that gives me better
cross fire gain at the expense of some end fire gain; and my verticals are
on a NW/SE line (NE/SW would be better, but that wouldn't work at my QTH).
I have mono band antennas for all the bands and only run one coax and two
rotor cables into the shack. I designed and built a remote switching system
that uses +, -, 0, and AC down the coax along with a hard wire to the first
relay box that I use the same voltages to swith the one coax out to the
first four runs to additional switch boxes. The only reason I have two
rotor lines is I needed a seperate one for the Orion 2800. All the other
rotors are Hy-Gain and I remote switch them so I only have one CDE (Hy Gain)
rotor box in the shack.
You might look into control voltage down the coax; and if you run a single
wire out to a coax switch box (like the Ameritron RCS-4) you can switch 16
antennas with four additional boxes. I have three of the RCS-4s along with
a couple of MFJ-4712's to do all my switching. I called them up and bought
just the relay boxes, and then modified them as necessary to work as I
needed them to.
I will say that I have been very pleased with the ComTek PVS-2 on 160M.
Good luck
Dick K8ZTT
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