Technician: Coax Lightning Protection

Which of these precautions should be taken when installing devices for lightning protection in a coaxial cable feed line?

A. Include a parallel bypass switch for each protector so that it can be switched out of the circuit when running high power
B. Include a series switch in the ground line of each protector to prevent RF overload from inadvertently damaging the protector
C. Keep the ground wires from each protector separate and connected to station ground
D. Mount all of the protectors on a metal plate that is in turn connected to an external ground rod

Let’s examine each of these potential answers and see what makes the most sense.  I don’t like this question because its throwing enough mumbo-jumbo at you to confuse you to the real meat of the question about coax lightning protection.

A.  Switching each protector out of the circuit makes no sense.  Additionally, they’re meant to take lightning hits, so running “high power” through them should have no effect at all.

B. Again, why would you concern yourself with protecting the protector?  That’s what its there to do!

C. This one could maybe work, but keeping the ground wires separate really has no bearing on anything, and is actually the opposite of what you want.

By elimination then, we’re left with D. Mount all of the protectors on a metal plate that is in turn connected to an external ground rod.

The typical and recommended installation of lightning arrestors is to mount them all so their grounds are connected to a common sheet of conductor, usually copper.  That is in turn connected by a strip of copper or a braid to your ground rod..  The reason for this is you want as much material as possible to take the brunt of a hit, not your equipment.  The flat copper sheets, straps and braid also keep RF at bay.

[T0A07] (This question is from the Technician pool that takes effect in July 2018)

(Image: https://commons.wikimedia.org/wiki/File:Polyphaser_(2400170454)_(2).jpg)

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