Your balanced feedline can also serve as your control lines.
With no voltage on the lines, one pair of wires is selected.
With +V on the lines, one of the relays is energized
With -V on the lines, the other relay is energized.
Use good quality RFC on both sides of the line at the shack and
antenna and you shouldn't have any problems.
Look at the diagrams in ARRL Antenna Handbook or ARRH Radio Handbook
for switching details.
I use this type scheme for switching relays in a phased array for 40m
and will do so, also, for 80m.
Quoting Gary Slagel <firstname.lastname@example.org>:
> Thanks everybody for the input. I feel myself getting
> ready for another one of my ill fated homebrew
> projects :) !! This SEEMS pretty straight forward but
> my homebrewing skill are pretty suspect so I'm going
> to ask for more help.
> I put a crude pencil drawing of what I'm trying to do
> with the relays here:
> I'm trying to implement a Cebik antenna idea he called
> a 'Y-doublet' (http://www.cebik.com/edz/wy.html).
> Basically 3 88' wires arranged in a Y spaced 120
> degrees from each other. By using 2 spdt relays I can
> select 2 of the 3 wires to make a 176' doublet which
> I'll feed with balanced line and tune from 10meters to
> 160meters. By selecting different combinations I can
> point 3 different directions. I'll put the relays in
> a box at the top of the tower and have one balanced
> line from there to the shack. I'll need 2 separate dc
> voltage control lines so I can control the relays
> independently of each other. I'll only run 100watts
> at first but want to run 1000W CW in the future. A
> couple questions:
>> From the feedback on this list I've got 3 different
> options for the relays and wondered which would be the
> most dependable: 1) Vacuum relays like the Jennings
> type RF1E-26N1137 on this page (
> ) 2) RF Open Frame relays like the Deltrol (KO)
> RNF100-SP on this page (
> http://www.surplussales.com/Relays/rfopen.html ) 3)
> Medium Amp Power Relays like the 7384k52 on this page
> ( search for part# 7384k52 at http://www.mcmaster.com/
> It was mentioned I'll need an rf choke on the dc
> control lines. Will that just be a ferrite core with
> the line wrapped around it a few times... or a ferrite
> core clipped on the line??
> Does this whole scheme look reasonable or am I doomed
> for another homebrew failure?
> Thanks to anyone taking the time to work through this
> thing with me!!
> Gary Slagel/N0SXX
> Lakewood, CO
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