[TowerTalk] Lightning Arrestors

[Doug Rehman]

Let me preface this with INAE (I'm Not An Engineer...); the below is based
on my practical experience in both public safety and amateur communications.
It is also based on the commonly seen protectors from ICE and Polyphaser.

As to which is "best", there are a lot of factors to consider and what is
"best" for one application isn't for another. I use a mix of ICE and
Polyphasers.

I have far more Polyphasers in service since new ones are often available on
eBay for a steep discount.

In my previous life overseeing the communications system for a state law
enforcement agency in Florida, I had Polyphasers installed on all of our
feedlines (remote control phone circuits and power too). This reduced the
summertime lightning damage from taking out a station about every other week
or so to only one or two stations per year. 

At least in the US, Polyphasers are used far more than any other brand in
commercial/government VHF/UHF applications. 

Pay attention to the frequency and power ratings- you don't want to fire the
gas discharge tube with your RF. Also take into consideration the VSWR of
the antenna- an unmatched antenna could cause the voltage in the protector
to go high enough to fire the tube even though the transmitter output power
is under the rated maximum.

For antennas with the potential for induced static charges (wind, lightning,
etc.), I use ICE protectors since the center conductor is at DC ground.
Since the Polyphasers are not at DC ground, the static charge will build
until it crosses the threshold for the gas tube to fire. In an installation
where static charge is a significant problem, the life of the protector
could be diminished by the continual firing to dissipate the static charge.

If you're using anything that requires voltage on the coax (remote antenna
switch, preamp, etc.), you'll either have to get a protector that is
specifically designed to pass the voltage or come up with an alternate
wiring plan.

Don't forget protectors for other wires coming into the shack such as the
rotator cable. You can find commercial products or just put MOV's across
each line to ground. (All of the commercial protectors I have looked at are
simply using MOV's- you're paying for the nice packaging.)

If you're running high power at VHF/UHF the choice of a protector may be
very limited. My 1.2KW on 6 meters required an ICE protector- it is well
beyond the rating of the commonly available Polyphasers.

All this reminds me- I just added a 2 meter KW amp and better go check what
the max power for the protector is...

Doug
K4AC