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I've been reading about grounding outdoor TV antennas but these terms seem to be used interchangeably by various articles on the internet.

For example, this article seems to make a distinction between (coaxial?) lightning arrestors and coaxial grounding blocks. It says:

  • "Mount the grounding block as close as possible to where the 75 ohm coaxial cable downlead enters the house"
  • "The antenna discharge unit (also called a “lightning arrestor”) is connected to the transmission line at a point close to where the transmission line enters the house"

So we should install both the grounding block and lightning arrestor near the place where the coax enters the house....

Ok, but what about this article: "To protect yourself from a direct strike, attach a lightening arrester (sic) to the antenna mast" (huh? I thought it goes near where the coax enters the house).

Lastly, this one says: "The coax cable itself can build up a static electric charge and in order to properly dissipate that charge an antenna discharge unit or grounding block can be used" (so now it seems an antenna discharge unit in fact isn't a lightening suppressor...)

This is all somewhat confusing to an antenna newbie like myself. Does anyone have a cogent explanation of these three items (and perhaps some indication of the ideal places they are installed)?

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Antennas can build up a sizeable static charge which needs to be dissipated. Unfortunately the obvious solution of grounding the antenna also removes the signal from the wire. A coaxial grounding block allows static charges to dissipate from the center conductor without interrupting the signal.

More elaborate devices are filled with a gas which is ionized by high voltage spikes to create a very low resistance connection to the ground. This allows lightning traveling through the cable to be arrested. Both grounding blocks and arrestors are discharge units, which dissipate the static charge from the antenna. Only the arrestor provides protection against lightning.

Ideally either would be installed as close to the point of entry as possible. The cable run itself has all the drawbacks of metal suspended in air. It can gather a static charge, and conduct lightning. Also, as the first article points out, you may need a second ground wire if the antenna is atop a metal mast. Though the mast can be connected directly to the ground, since signal loss isn't an issue.

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    That's mostly right, but grounding blocks connect the outer shield to ground, not the inner conductor. Grounding the inner conductor would be bad for passing signals, which is why lightning arrestors only ground the inner conductor when there's a high voltage on it.
    – mrog
    Nov 16, 2018 at 20:57
  • It seems you're saying if the antenna contains a pre-amplifier (or if we install one additionally), then we should use both a coaxial grounding block and coaxial lightening arrestor? Otherwise, we're probably good to go with just the coaxial grounding block?
    – orlando21
    Nov 17, 2018 at 6:36
  • You need one or the other (both are discharge units). The grounding block is likely cheaper, but you'll probably want a lightning arrestor if your home is at a high risk of lightning strikes. (Which depends on location, surroundings, etc.) There may not be a huge price difference though, arrestors are required on phone lines so it's hardly a new-fangled technology.
    – Matthew Gauthier
    Nov 18, 2018 at 12:07

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