Grounding antenna masts and coax cable - Page 5 - AVS Forum | Home Theater Discussions And Reviews
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post #121 of 124 Old 06-19-2019, 06:51 AM
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Actually,you should always ground a attic mounted antenna the same as one on the roof.
Lightning travels miles through open air so 3\4 inch of plywood and shingles won't stop it.
And even though the NEC has finally began to improve their grounding codes after decades of people like me complaining, they still have room for improvement on antenna grounding which may take another decade or two for them to finally change
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post #122 of 124 Old 06-19-2019, 07:01 AM
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Quote:
Originally Posted by J_ph View Post
What happened to my coax?

I have a CM4228hd antenna and CM7777 amp. There is a ground from the antenna and on the block that enters the house. This "burned" or corroded coax is at a coupling in the external coax cable. The black on the outside is just residue from electrical tape. It was sealed with the tape, and neither the tape or outer coax showed any signs of distress, just the inside. I've replaced the coupling and packed the connection with dielectric grease. Is this the result of water in the cable?

thanks in advance!
Water and current are a bad mix inside a connection.
And if you are using steel center conductor coax it makes it even worse.
Always seal coax connections with "coax seal" or similar butyl rubber coax wrap.
The connections atop every 400 foot cell tower are always sealed that way for good reason.
And they don't ever use grease in connectors.
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post #123 of 124 Old 06-21-2019, 11:06 AM
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Quote:
Originally Posted by old tv guy View Post
Actually,you should always ground a attic mounted antenna the same as one on the roof.
Lightning travels miles through open air so 3\4 inch of plywood and shingles won't stop it.
And even though the NEC has finally began to improve their grounding codes after decades of people like me complaining, they still have room for improvement on antenna grounding which may take another decade or two for them to finally change
???

I followed the evolution of the code from 1999 to 2011. Mast grounded with 10 gauge copper, 8 gauge aluminum or 17 gauge copper clad steel, to an 8' x 1/2" dia ground rod, bonded to the ground electrode system with 6 gauge copper wire.. Outer coax grounded to the ground electrode system as near as possible to the point where it enters the building with wire approximately equal in current carrying capacity as the shield itself.

They did prohibit using the copper water pipe for that ground I think in 2002, not because it was technically deficient, but rather, because it's ground path could be broached by subsequent plumbing repair with plastic pipe. I think that in 2011 they put a limit on how far the ground wire path of the mast ground could veer laterally from straight down, but that really wasn't an improvement because the purpose of that wire was to drain static discharge, not to draw the lightning current away from other paths.

An antenna in an attic doesn't tend to "attract" lightning because it is not the highest metallic object and is not subject to developing a static charge due to the wind blowing across its elements.

Last edited by AntAltMike; 06-24-2019 at 09:37 AM.
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post #124 of 124 Old 06-21-2019, 06:35 PM
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I was doing single point grounding years before the NEC finally woke up and corrected their grounding codes and i still feel they have plenty of room for improvement when it
comes to gounding of antennas.
While the NEC has completely different grounding codes for air terminals, they still havn't recognized that roof mounted antennas act just like air terminals when hit by lightning.
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