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Old 23-Jul-2019, 3:52 PM   #30
GroundUrMast
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Join Date: Oct 2010
Location: Greater Seattle Area
Posts: 4,749
Quote:
Originally Posted by RMinNJ View Post
So the ground block for the coax should;

a.) Not be up by the antenna or in the house?
b.) Should not be in series with the the mast ground wire ?

What that means for me is running more coax from the antenna down near the grounding rod and where my cable TV input already has a ground block. I had always thought the best way was to put the coax directly into the house from the antenna and keep it short as possible.
There are often competing factors to deal with. Whether it's a family member that wants the antenna to be hidden from view or keeping costs under control...

While keeping coax length to a minimum makes sense in terms of signal quality, the safety of the installation may argue for a less than ideal length of coax.

To your points specifically,

I have concluded that placement of the coax ground block very near the electrical service ground makes very good sense in most cases. Should the coax be struck by lightning or get crossed up with power, I don't want the fault current to have to travel inside the building on it's way to the ground connection. Mounting the antenna away from power lines is an obvious step that will reduce the chance of ever getting crossed up with heavy power... But if that did occur one could expect the coax to act as a fuse which is why I would take steps to make that occur outside the building. After the ground connection, I want as little coax exposed to the outside as possible. The most likely source of fault current inside the building would be from electrical branch circuits which have a breaker or fuse to limit the time a high current fault can last.

I would keep the mast ground separate from the coax ground because the sources of fault current in contact with the mast are outdoors so likely not fused. If I connect the mast to my coax, the coax will be forced to conduct some of the current if a fault exists. I'd rather provide my mast a single path to ground, entirely outside the building and with no connection to the interior.

When the mast and coax grounds come together at the electrical service ground, there is a minimum amount of resistance between each part of the antenna system and ground... Therefor, if fault current flows the voltage drop will be as low as possible.
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Last edited by GroundUrMast; 26-Jul-2019 at 4:50 AM. Reason: sp.
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