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[TowerTalk] relays

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Subject: [TowerTalk] relays
From: (Malcolm Clark)
Date: Fri, 10 Apr 1998 20:59:00 +0000
Barry Kutner wrote:


> I thought I'd put the relay at the end of the phone-band wire, and
> add 10 ft (or whatever it takes to resonate at CW) on the other side
> of the relay. Could control with a 12VDC line to the relay. Do you
> see a problem here?

I sure do.  For one thing the relays are going to have to be mounted to
or on something.  And that something is going to have to be supported
somehow.  If any of the support structure is anything but an excellent
insulator you will couple RF into it.  Even if you can get around that
problem, the control lines will be conductors which are going to be
coupled into to some degree.  If you come away from the sloper at a
right angle you will minimize the coupling but I expect you would still
get some detuning.

Perhaps you might be able to mount the relays directly to the sloper
wire itself, with a non-conducting jumper bridging around the relay to
provide the physical connection between the CW addition and the main
section .  The control lines, which would have to have excellent
insulation, might be tied tightly to the main radiators with chokes at
the feed point to decouple the RF.  That might do the trick.  I think
you would require four chokes--one on each half of each control pair.  I
would also twist the control pairs to minimize any RF difference of
potential across the relay coil.

The relays would have to be weather-proof with an adequate
rating--whatever it is.  The hermetically sealed variety comes to mind
as a potential candidate.

Good luck.

73 Malcolm KR4HP

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