The Ameritron 4-pos antenna switch accomplishes this trick. It sends low DC
voltages down the coax to operate the antenna switching relays. I know it uses
some RF blocking capacitors, but I can't recall the values. It may also use at
least one RF choke. The schematic supplied with the unit clearly shows all of
this, and you should be able to use it to design your unit. Perhaps someone on
Tower Talk can send you a copy.
73, Dick, WC1M
From: Dale L. Martin . <firstname.lastname@example.org>
To: Tower Reflector . <email@example.com>
Date: Friday, December 19, 1997 2:04 AM
Subject: [TowerTalk] RF & DC coupling/decoupling
>I have checked my resources here in the shack (ARRL Handbook and ARRL
>Antenna Handbook and beaucoup issues of old QST's) and find nothing to help
>me in my quest to the following question:
>What components are needed to couple/decouple a DC control voltage (13.8v)
>on a coaxial cable which will also carry 500 W RF?
>Does anyone have a working system such as this? I've seen them
>referenced/described in the past, but now that I need it, I can't find any
>info on it.
>What component values of C1, L1, C2 and L2 work? Are there any other
>additional components used? If you have such a system, are you been
>satisfied with the performance?
>I have a marine vertical antenna and automatic antenna tuner at the end of a
>600 foot run of 7/8" hard-line. Rather than install a power supply in a
>nearby rooftop equipment room, I would like to see if coupling/decoupling
>the DC would work in it's place.
>Thanks in advance for any information.
>(apologies if this is not Tower related, but they won't let me put up a
>tower on the roof directly above the station).
>Dale Martin, KG5U
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