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I am installing 2 antenna masts on one end of my house. The utility ground is on the far end of the house, and was buried under the asphalt driveway.

Working with my electrician, he suggests 2 ground rods by the 2 masts and 2 ground rods at the entry point for the coax to the house. the rods in the 2 groups will be spaced at least 8' apart.

The antennas will be ~60' from the house and the utility ground and the 2 new grounds by the house will be ~80' apart.

schematic

simulate this circuit – Schematic created using CircuitLab

Because of the distance, and being under the driveway, bonding the 2 sets of grounding rods together will be difficult. It would end up being approx 200' of wire to get around the house and then digging a trench in the driveway to find the ground rod, and then fixing the driveway.

What are the consequences of not bonding the new rods with the existing ground rod? Is there something else I can do to mitigate the issues?

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    $\begingroup$ Does the utility ground rod have a cable that appears next to the house? Can you make a simple sketch using the circuit diagram feature? $\endgroup$
    – tomnexus
    Sep 29 at 16:22
  • $\begingroup$ The only exposed wire i see is the ground from the cable companies coax. It goes down under the asphalt. It's a 10awg. $\endgroup$
    – mbond
    Sep 29 at 16:41
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    $\begingroup$ Running 200' of appropriately sized wire is a lot cheaper than your house burning down, or running the shack off a separate generator hooked into your antenna ground system. $\endgroup$
    – Jon Custer
    Sep 29 at 19:06

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Consequence 1: it's not up to code. A contractor shouldn't do it that way, and if you do it yourself, it might make it difficult for you to sell your house (if you don't take everything down beforehand), or make it difficult for you to recover from insurance if anything happens to your house. Worst case, your house burns down from a lightning strike and you end up with no house, no shack, and no money.

Consequence 2: ground potential rise. When there's a lightning strike nearby, the potential of "ground" at two points a few hundred feet apart can differ briefly by hundreds or thousands of volts. If your ground rods are bonded the way that they should be, the current that equalizes that voltage difference will mostly flow through the bonding conductors. If they aren't, then it will flow through any other path it can find, i.e. from the tower ground to your coax, from the coax to the chassis of your radio, from the chassis of the radio to the power supply ground, and from there to your utility grounding rod. This is bad because it goes through your radio, but it's also bad because it goes through your house, and you don't want it to go through your house.

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  • $\begingroup$ Doesn't sound like i'm going to be able to short cut this. thanks. $\endgroup$
    – mbond
    Sep 30 at 1:35

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