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[Towertalk] Supressors that pass DC control V.

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Subject: [Towertalk] Supressors that pass DC control V.
From: (
Date: Fri, 27 Sep 2002 15:34:08 +0000
I think Jon's got it!  Place the DC bias tee on the 
tower side of the coax suppressor and then run the DC 
voltage wires into a Polyphaser or ICE rotator control 
wire suppressor.  Now everything should work and all 
cables into the shack are protected.  Phil  KB9CRY
> on 9/26/02 11:50 AM, at wrote:
> > I wrote Polyphaser and ICE and both indicated that they do not manufacture
> > a HF/KW rated surge supressor for coax, that passes DC (for coax switch
> > control).
> > 
> > I guess I'm going to have to pull some cable through the conduit and 
> > fabricate
> > another switching arrangement (and then shunt that DC path with some husky
> > MOVs)
> > to accomplish remote switching with a quality surge arrestor in line.
> It was interesting reading the Polyphaser rationale behind this and it makes
> sense.
> If your tower is hit, there will be lightning energy on both the outer
> shield of your coax and the inner conductor.  The energy on the shield will
> reach the suppressor first with the inner conductor being delayed because of
> the slower propagation velocity factor of the coax.  It will also be spread
> out in time.  This time delay will create a voltage potential between the
> shield and the center conductor.  If the center conductor has DC continuity
> through the suppressor, your equipment will see that potential.  That's the
> problem.
> What I would suggest you do is make yourself a pair of Bias Tees.  Put one
> on the radio side of your suppressor and one after the suppressor.  Connect
> the DC feeds together.  Now, you do have a DC continuity still, but if your
> inductor is large enough, it should look like an open circuit initially to
> the energy of a lightning strike.  Perhaps that still defeats the purpose of
> DC blocking in the suppressor.  Maybe someone more qualified can comment on
> that.
> Alternatively, just use one bias Tee in the antenna side.  Then you just
> need to run a DC control cable to wherever your suppressors are located and
> you don't need to worry about running a different line up your tower, etc.
> Hope this helps.
> 73,
> Jon
> NA9D
> -------------------------------------
> Jon Ogden
> NA9D (ex: KE9NA)
> Life Member: ARRL, NRA
> Member:  AMSAT, DXCC
> "A life lived in fear is a life half lived."
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