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I've seen ham radio antennas that slide over a vent stack. The usually way to connect them to the transceiver is to lay the feedline across the roof. However, the manufacturer provides instructions for hiding the feedline inside the vent. They suggest poking a hole in the existing vent and sealing it around the feedline.

I'd like to do something similar, except in my case I'd like to replace an abandoned weatherhead (which used to run to the load center) with a PVC pipe which looks like just another vent pipe. I'd check to make sure the weatherhead really is disconnected from the house wiring first. Then I'd put an antenna inside this PVC pipe. There are a few advantages to this:

  1. I can get rid of part of the ugly weatherhead.
  2. I don't have to re-do the flashing around the vent.
  3. I'll gain a 2m / 70cm antenna on the roof.
  4. Since the PVC pipe isn't really a vent at all, I'm free to run the feedline through it instead of across the top of the roof.

However, I'm concerned about proper lightning protection. I don't live in an area with much lightning, but what's preventing lightning from striking my PVC pipe antenna and traveling down the shield of my feedline inside the attic down to my transceiver? The Ventenna article I reference makes no mention of lightning protection. Is there something intrinsic about a PVC vent stack antenna that obviates the need for lightning protection on the feedline when the feedline goes inside the vent itself?

If I did want to provide some lightning protection on my feedline, how should I do that? I don't want sparks inside the attic. I might just end up with a smoldering fire in the 50-year old cellulose insulation that burns down the structure at a later date.

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Protecting equipment and property with an antenna such as this is no different than with any other antenna. See How can I protect equipment against a lightning strike?

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  • $\begingroup$ I guess I was looking for answers such as, "You can't run the feedline down the vent pipe. It needs to run exterior to the house until it gets to a grounded Polyphasor. The Ventanna company's instructions are bogus." OK. That's not quite the answer I'm looking for. I guess I'd like to see an answer pertaining to the specific case of a feedline entering the the structure in the middle of the roof instead of on the side near the ground rod. $\endgroup$
    – watkipet
    Commented Jul 9, 2020 at 13:42
  • $\begingroup$ @watkipet unless you have a ground rod in the middle of your house, how will you simultaneously run the feedline inside the house and end at a single point ground? $\endgroup$
    – Phil Frost - W8II
    Commented Jul 9, 2020 at 22:25
  • $\begingroup$ Frost--Good point. However, even if I did have a ground rod in the middle of my house--isn't that a bad place to dissipate energy from lightning? $\endgroup$
    – watkipet
    Commented Jul 9, 2020 at 23:35
  • $\begingroup$ @watkipet sounds like a new question to me. $\endgroup$
    – Phil Frost - W8II
    Commented Jul 10, 2020 at 4:34
  • $\begingroup$ Frost OK, I'll try and come up with a new question. $\endgroup$
    – watkipet
    Commented Jul 10, 2020 at 14:14

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