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In Reply to: Grounding Antenna posted by jcmusic on January 24, 2007 at 10:22:23:
First, be aware that there are NEC rules that need to be followed when installing an antenna. The literature which came with your antenna should include some notes and an illustration showing a typical installation. But if you're not sure, it's best to consult the NEC or talk to an electrical inspector in your town.Do you know whether the ground rod was necessary in your case? If you can run the antenna feed such that it enters the house close to your existing electrical/cable/phone service entrance, then it is simpler and safer to ground everything there rather than to a separate ground rod. A new ground rod should only be necessary if you're bringing the antenna feed into the house a long way away from a suitable grounding point (I forget the distance limit but it's something like 30 feet).
Anyway, you need to install a coax cable grounding block at the point where the cable enters the house. Assuming the ground rod is necessary, it should be installed as close as possible to the grounding block. Then the ground wire from the mast and the ground wire from the grounding block should meet at the ground rod. The minimum wire sizes depend on the length of the runs; #8 or #10 for a typical rooftop to ground run. Last but not least, it is _critically_ important that you run another #6 or larger ground wire connecting the new ground rod to a suitable ground bonding point in the existing electrical system. Without this, ground potential differences due to a nearby lightning strike or ground fault may drive large currents through your tuner and house wiring.
When grounding the antenna mast, make sure the antenna boom, tripod and any additional bracketry (if applicable) are all grounded. In my case, this meant running an additional ground strap from the mast below the rotor to the mast above it. Finally, if you live in a lightning prone area, you may also want to consider running the antenna feed through a lightning arrestor.
Hope this helps,
Follow Ups:
Hi Dave,
As far as the antenna it is already up, the cable enters the house through the attic vent on the roof. I put the ground rod because I knew the mast had to be grounded, and it is not close to the house ground. So you see I just wanted to know if I could use the grounding block for the cable, and the ground on the mast together.
Are you trying to be code compliant or just trying to do something reasonable? I believe the distance between the coax grounding block and a suitable grounding point is supposed to be within a certain limit, like 20 or 30 ft., and I know the grounding block is supposed to be located where the cable enters the house. Depending on how high the attic vent is, you may or may not be able to simultaneously satisfy both requirements. But even if it's not NEC compliant, tying the grounding block to the mast ground seems reasonable in this case.The big issue is the ground rod. You can't just add another ground rod without connecting it to the existing grounding system - that's a major safety hazard. So you'll have to run another #6 or bigger ground wire from the ground rod to a suitable ground bonding point at the service entrance. A suitable bonding point includes the existing grounding electrode if it's accessible, a ground pigtail provided by the electrical utility at the meter can, metal conduit entering the service panel, or other options listed in the NEC. You _must_ do this for safety in the event of a nearby lightning strike or ground fault, and it should also help to prevent ground loop issues.
David I am not try to be in compliance, I am just trying to everything grounded so that nothing gets damaged in the event it takes a hit.
I think the important issues are 1) what is the right thing to do from a safety standpoint and 2) what will not give your insurance company a reason to not pay a claim in case there is a lightning hit with damage.
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