[TowerTalk] homebrew low voltage surge suppressors?

[Gary Schafer]

Go to Mouser or anyone else that sells large MOV's. Buy a bunch of them. Put
one to ground on each control line. That is ALL that there is in the
Polyphaser rotor protector box.

Keep in mind that the surge energy will be pretty much divided among all
control lines and coax by the time it gets to the shack. So any one line
will not be carrying a great amount of energy and the MOV's will easily
handle it.

If you have only a couple of lines to protect then you need a little more
sophisticated type unit consisting of a gas tube, inductance and MOV. But
with multiple lines the full energy is divided and no one line carries a
great amount of energy.
Also the long, I assume underground path, of the cables to the shack will
choke off a great deal of energy.

There is usually not a need for additional protection devices at the bottom
of the tower, only at the shack entrance at your single point ground plate.
But if you are going to run the lines in metal conduit to the shack then it
is a good idea to put a set of MOV's at the tower base also because you
don't want a large difference in potential between the lines and the conduit
as they may arc to the conduit and damage the cables.

The coax is no problem. No protectors needed at the tower base just ground
the shields at the base and ground the metal conduit to the shields if that
is what you are using to transport the cables to the shack. Again this is
done to prevent any difference in potential between the cable shield and the
conduit where it could arc and damage the cable. 

73
Gary  K4FMX


> -----Original Message-----
> From: towertalk-bounces at contesting.com [mailto:towertalk-
> bounces at contesting.com] On Behalf Of Dick Green WC1M
> Sent: Wednesday, September 27, 2006 9:36 AM
> To: Tower
> Subject: [TowerTalk] homebrew low voltage surge suppressors?
> 
> My new tower will have three 4-el SteppIRs, three TIC rings, a T2X, a
> stack
> match and an SO2R switch box. That comes to 96 control wires. Since the
> tower is over 200 feet from the shack, it's best to have a surge
> suppressor
> at both ends of each wire. I used Polyphaser RCT surge suppressors for my
> other tower, but the price has about doubled since I did that. I'm looking
> at close to $3,000 worth of RCT surge suppressors. Besides, the RCT
> mounting
> hardware is really designed to clamp to a tower leg and I'll be mounting
> the
> suppressors on ground panels inside metal NEMA boxes. I've done that
> before
> and wasn't real happy with the result. Even if I go with the ICE units,
> which have better mounting, the cost will be quite high.
> 
> So, I'm wondering if anyone has seen or designed a homebrew low voltage
> surge suppressor circuit? My understanding is that it takes more than just
> low voltage MOVs. You need series inductance and/or resistance and a
> diode.
> I haven't found anything appropriate on the web. Can someone point me to a
> schematic and/or tell me how they did it?
> 
> 73, Dick WC1M
> 
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