power is carried in the feedline. In an ideal system, you'd
have the
reactance at the antenna, so that the feedline is at 50
ohms, and all the
box needs to do is generate the right phases. Of course,
the matching
network at the antenna would then need to have multiple
values, since the
feedpoint impedance changes with the array steering
direction. And, it
would be quite "challenging" to tune up (broadcast antenna
engineers earn
their pennies doing this).>>
That is like a system I built for someone else.
Each outer antenna tower has a matching system for four
impedances. The common tower has a matching system for three
impedances (omni) (N E S W patterns) and (NE SE NW SW
patterns).
The ATU's always present a 50 ohm load to the lines, and the
main phasing box (about five feet tall and four feet wide)
in combination with the ATU's has about 35-40 edge wound
inductors, around one hundred capacitors, and probably 30 or
so relays. A partially completed photo at:
http://www.w8ji.com/images/W8JI%20site/phasor1.jpg
My own personal system is on plywood with copper overlay as
a ground plane, and uses transmission lines and T networks
for delay. Most of the components are just glued down.
_______________________________________________
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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