Grounding antenna masts and coax cable - Page 5 - AVS Forum | Home Theater Discussions And Reviews
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post #121 of 131 Old 06-19-2019, 07:51 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 131 Old 06-19-2019, 08:01 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 131 Old 06-21-2019, 12:06 PM
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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 10:37 AM.
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post #124 of 131 Old 06-21-2019, 07:35 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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post #125 of 131 Old 09-08-2019, 09:20 AM
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Quote:
Originally Posted by old tv guy View Post
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.
I'm late to the party but I didn't think the NEC (NFPA 70) addresses lightning, it is an electrical safety spec. Lightning protection is covered by NFPA 780.
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post #126 of 131 Old 10-09-2019, 05:52 PM
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I'm getting different NEC standards on this, so I nwated to ask on the forutm, syould you only run a ground to the mast and ground block / lightning artrestor, or should the mount also have a dedicated ground wire ran to it? Or only for certain types of mounts (if so, which m ount types require a dedicated ground wire)?
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post #127 of 131 Old 10-09-2019, 08:15 PM
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I realize the coax cable should be grounded by a ground block or lightning arresstor per NEC code and also the bottom of the mast should be grounded. What about the mount that holes the mast? I found a few old manuals that mention it, but everythign recent doesn't even mentioned also grounding the mount. Is it necessary?
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post #128 of 131 Old 10-10-2019, 08:28 AM
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Quote:
Originally Posted by scott55t View Post
I realize the coax cable should be grounded by a ground block or lightning arresstor per NEC code and also the bottom of the mast should be grounded. What about the mount that holes the mast? I found a few old manuals that mention it, but everythign recent doesn't even mentioned also grounding the mount. Is it necessary?
Hello, scott55t; welcome to the forum.

Quote:
NFPA 70®
National Electrical Code®
2014 Edition
810.15 Grounding. Masts and metal structures supporting
antennas shall be grounded in accordance with 810.21.

810.20 Antenna Discharge Units - Receiving Stations.
(C) Grounding. The antenna discharge unit shall be
grounded in accordance with 810.21.
The code is ambiguous. I'm not a code expert, but my interpretation is that you only need two grounding conductors, one for the grounding block (ADU) and one for the mast, because the mast is higher than the mount and the mount is already bonded to the mast. However, the interpretation by the AHJ (Authority Having Jurisdiction), who is usually the local electrical inspector, becomes the local law that is binding on you.

If the antenna is outside, the coax shield should be grounded with a grounding block that is connected to the house electrical system ground with 10 gauge copper wire for electrical safety and to reject interference. For further compliance with the electrical code (NEC), the mast should also be grounded in a similar manner to drain any buildup of static charge which will tend to discourage a strike, but the system will not survive a direct strike.


If you can not measure it, you can not improve it.
Lord Kelvin, 1883
www.megalithia.com/elect/aerialsite/dttpoorman.html
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post #129 of 131 Old 10-10-2019, 03:23 PM
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Outdoor channel master tv antenna grounding question

Hello all and thanks for having me. I need some advice and joined this forum hoping to be pointed in the right direction.

First off I am not an electrician and dont know the first thing about grounding or wiring. I will try to explain it the best I can.

I recently moved to Middle Tennessee in a very rural area. No cable tv or internet is currently available at the home we purchased with a few acres. Did I mention cell phones barely get a signal out here and only ar&t work we had to switch over upon moving here.

I bought a small indoor tv antenna and stuck it in the window and we were able to pull in only 4 channels. On some days if I rescan we can get 7 or 8 but can rarely watch them as they pixelize and disaapear.

I talked to a couple people at a local market who have old school tv antennas (not cheap modern chinese crap) and are picking up 50-70 channels from nashville and even some from Huntsville Alabama. I stopped by my nearest neighbors house to see his set up and he does in fact pull in far more channels than I imagined.

Out in my yard I have a antenna mast tower approx. 20 ft high with no antenna on it. Its heavy duty and in the perfect place on the property to pull in a signal from Nashville 60 miles away to the north. 100 ft from the antenna mast is my living room wall where our tv is located.

So I went to channelmaster and purchased the longest range outdoor antenna they had (after weeks of researching antennas) I will attach a photo of the antenna. Its rated at 100 miles, im aware its debatable if a vhf signal can reach an antenna at 100 miles but I wanted the best chance at doing so. The transmission towers im after are 60-70 miles and Im getting a few with a $20 walmart indoor antenna. Buying this big boy for outside and having it high up on a mast has to increase my chances to pick up the signals.

The antenna I purchased does not have a motorized rotor as I didnt want to run electricity to the mast. Just point it in the degrees of Nashville and bolt it down as my neighbors have done. I purchased the antenna and a pre amp booster suggested for my zip code by channel master. The pre amp does not require its own electric as it works by taking electric it receives from the coaxial cable it uses to attach to the antenna. Antenna and booster arriving tomorrow.

I then started thinking about the need for grounding the antenna and the coaxial cable so purchased a coax ground block and a spool of #10 solid copper grounding wire. I also purchased a 5 ft copper grounding rod to ground both the antenna mast and the coaxial cable at the mast and have 120 ft of burial coaxial cable running to the house under ground. I thought everything out carefully as fas as parts and supplies I would need. Today I went out and sunk the grounding rod into the soil near the mast leaving only the top 6" sticking up so I can attach my copper.

I came in the house and started reading a little about grounding to make sure I would do it right and now I am not confident that I am. Most articles I find pertain to antennas mounted on the roof of the home. And the antennas are grounded to the homes main ground under the electric panel outside of the house.

My antenna is going to be on a stand alone mast 100+ feet away from the house all by itself out in the field nowhere near the homes main ground. The electric panel and main ground for the house couldn't be any further away than they are, completely on the opposite end of the property's. Im talking polar opposites! I am also now reading that 8' ground rods are needed?


So keep in mind this antenna is on a stand alone mast and not powered. The little booster add on is powered but from the coaxial cable that carries a charge from inside the house where an ac adapter is plugged in that the coaxial cable runs through.

I had it all planned out for a clean neat install of an antenna that besides the coaxial just had 2 U clamps . Now this simple tv antenna is turning into a whole big thing.

Can someone tell me that its ok to ground the mast (pictured) and coax to its own grounding rod and not have to buy a country mile of copper wire and dig for a week to tie it in to the main ground of the home. I have to make sure this is safe and will work.

I know to an electrician this stuff sounds simple but again I am no electrician and I will appreciate whatever advice you can give me.

Also I would like to place the full blame for this project getting started on Eva Gabor. With only 4 channels I got hooked on Green Acres and devoloped a little crush on Miss Gabor. Now they switched networks and the new transmitter with green acres is a little further out. If you ever saw Miss Gabor you can understand my urgency.

Thanks to anyone who helps bring Eve Gabor back into my life
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post #130 of 131 Old 10-11-2019, 07:24 AM
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post #131 of 131 Old 10-11-2019, 10:22 AM
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Quote:
Originally Posted by Joev1983 View Post

Can someone tell me that its ok to ground the mast (pictured) and coax to its own grounding rod and not have to buy a country mile of copper wire and dig for a week to tie it in to the main ground of the home. I have to make sure this is safe and will work.

I know to an electrician this stuff sounds simple but again I am no electrician and I will appreciate whatever advice you can give me.
I'm sure others will chime in with additional info, but as I understand it, 8ft Ground rods are UL listed, while 4ft are not, although both are sold as ground rods and "can" be used ... If sticking with 4ft, you may want to put 2 or 3 in and bond them to each other ....
As far as the electrical ground being 58 thousand yards from the TV mast, there are many TV AC outlet "surge supressors/EMI filters" that also have an "F" coax in/out on them, that grounds your lead in coax to the outlet's/electrical system ground ... I'd probably do that, & combined with your separate grounding at the mast site of both the lead in coax and mast, you would be good to go ...
It's not 100% by the book, but by no means inadequate ...

Last edited by MeatChicken; 10-12-2019 at 09:38 AM.
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