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Vertical Antenna on Metal Roof: DC Ground to the Electrical Service Mast?

May 27th 2012, 03:59

KF7K

Joined: Apr 7th 2003, 14:05
Total Topics: 0
Total Posts: 0
I'm thinking of putting a multi-band trap vertical antenna in the middle of my metal-shingled house. I'll use radials laid over the roof as the RF ground system, but I am considering using the electrical service mast, only 8-10 feet away from the vertical, as a DC ground for the feedline lightning arrestor (there is a second ground point at the bottom of the feedline, just before it enters the house-grounded into a ground rod).

Will my plan make the power company mad?
Is my plan just asking to pull household EMI into the antenna?
Will a ground at the antenna make my house-wide electrical ground act like one huge radial?

I guess my question, deep down, is the role of the coax shield--how do I tell if it has lots of RF voltage on it relative to the house ground? Both are grounded to a rod, just at different places, but I know RF doesn't act much like like DC, and sadly I think in terms of DC.
Jun 10th 2012, 18:36

KF5SQL

Joined: Apr 16th 2012, 17:47
Total Topics: 0
Total Posts: 0
Will it make the power company angry? Not likely, think about it the cable or satellite companies ground to the power box poles or anything metal that they can find. I have seen them ground to a gas pipe. (Needless to say I called the cable company and told them about the unsafe practices of grounding an RF charged cable that over long distance attracts static electricity and then grounds it to an explosive source.) Most common ground point for telecommunications is in fact a power pole.

EMI is a different story, you may not pull EMI into your antenna, however you could possibly feed EMI into your household power which could cause interference on televisions in your house.

The method I have used is a direct ground from antenna to the ground rod.
Jun 11th 2012, 18:24

WB1GCM

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
It appears that your antenna would be located near the power line that comes into your home. Please, do not mount an antenna at a place that if it fell over, could come in contact with a power line. Besides the deadly effects, the antenna laying across the power line will likely cause your house to burn down. An insurance company would never pay the claim.

Thanks for listening; be safe.

Bob Allison
WB1GCM
ARRL Test Engineer



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