Topband: Shunt feedint the tower

N2TK, Tony tony.kaz at
Tue Feb 21 12:48:31 EST 2006

Well, 160M seems to be working fine with shunt feeding the tower. I like the
increase I got in bandwidth by making a multi-wire array parallel to the
tower face for the shunt feed instead of just using a #12 wire.

I picked up a  UV resistant water tight plastic box to hold 3 vacuum
variable caps and a vacuum relay. This way I can switch what part of the
band I want to cover with a flick of the switch from the shack. I am using
an omega match.

I do have a few questions:
-          With the 26V line to the vacuum relay, should I add an inline
choke and caps across the two wires? What value choke would be fine? Any
other things I should do with the DC supply for the relay so as not to have
RF issues?
-          I will bring the coax into the box with a water tight connector.
Will hook up the shield of the coax to the ground side of the one cap. Plan
on running a #12 wire to the closest tower leg – about 1’. Using a zinc
ground clamp on the tower leg. Any reason I should use something other than
#12 wire for the ground?
-          The coax will go to the coax switch mounted below this box. I use
the remote switch for selecting 40, 80 and 160M antennas. The switch is
grounded to the tower leg. The coax will be about 3’ long, at most. Is there
any reason to put on several large ferrite cores that will slip over the
Buryflex between the cap and the coax switch?
-          Any other input?

N2TK, Tony

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