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Here is my situation. My antenna mast is on the opposite side of the house from my ham shack, same with the power service entrance. I have installed ground rods roughly every 16 feet with #6 wire bonding everything starting at my power service entrance, continuing to the mast, polyphasers on an SPGP of sorts, around to the ham shack.

My coax is buried from the mast to where the polyphasers are going in. My plan is to run the coax from the protected side of the polyphasers up through the soffit and through my attic over to the HAM shack. The shack ground will enter from the side wall. The reason I am planning on doing it this way is my walls are brick and concrete, and it is a lot easier to drill a small hole for the ground wire than to core out a hole big enough for the ground and coax. Is there anything wrong with this approach?

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I compliment you on the multiple ground rods, the wide spacing, and having them all bonded to the service entrance ground. This meets NEC requirements while providing an improved lightning ground system.

I think your system is quite good as described. My suggestions for possible improvements are:

  • Use exothermic bonding (e.g. Cadweld) for your ground wire to ground rod connections. This results in lower maintenance and lower resistance per connection.

  • Increase the gauge of the wire or use copper straps between the added ground rods. This lowers resistance and inductance between the rods.

  • Put another Polyphaser in your shack by your radio. This improves the lightning protection and provides redundancy in the event of a Polyphaser failure.

There is a new ARRL book by Ward Silver on grounding. I have not read it yet but it might give you some other pointers.

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  • $\begingroup$ What do you think of this suggested grounding layout by W8JI? $\endgroup$ – Mike Waters Aug 11 '17 at 20:15
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    $\begingroup$ I have seen that before and am still surprised at the lack of lightning arrestors at the house entrance or station. $\endgroup$ – Glenn W9IQ Aug 11 '17 at 20:29
  • $\begingroup$ That's an interesting thought, Glenn. If you mean Tom's page, whatever he is doing must be working, as he claims that he never unplugs a thing during a thunderstorm yet has never had anything in his shack damaged. (I believe him). That page may not fully describe what he does; I may have read something else by him somewhere else. The idea is to have everything in the house and shack rise to the same voltage during a direct strike. $\endgroup$ – Mike Waters Aug 11 '17 at 21:35
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    $\begingroup$ Almost all the strike current will travel on the shield: because it's bigger and has lower inductance, and because lightning is a common-mode surge and will tend to migrate to the outside of the coax. So the single point ground is where you get most of the protection, lightning arrestors or not. $\endgroup$ – Phil Frost - W8II Aug 12 '17 at 13:12
  • $\begingroup$ @PhilFrost-W8II Exactly! However, your surge protectors are still a good idea. $\endgroup$ – Mike Waters Aug 12 '17 at 19:45
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Your setup looks pretty good. Bonding the grounds together is a step often overlooked, and substantially reduces the risk of lightning damage. There are still improvements that could be made however, and you'll have to decide if they are worth the effort and cost, according to the value of your radios and probability of lightning strikes in your area.

The good news is I believe your installation satisfies most of the common building and fire codes, and your homeowner's insurance may cover damage if there is a strike. However I'm not a certified electrician, so having a professional check your work is not a bad idea. And some insurance policies may require a rider to cover lightning damage.


Consider that all your connections are made by wire which has a non-zero resistance, and which encircle a large area and thus have a non-zero inductance.

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Schematically, and simplified, you have this:

schematic

simulate this circuit – Schematic created using CircuitLab

R1 represents the non-zero resistance of the Earth. I1 is the strike current passing through it. It could be due to a strike on the power lines, the tower, or even a nearby strike on the ground or a tree.

L1 represents your connection between the grounds.

What's the voltage across the radio?

You can't move the ground rods closer, so you can't reduce L1. You could use wide copper strap to reduce the inductance to a point, although that can get quite expensive. You can't change the Earth, and you can't stop lightning.

Really the only solution here is to have only one connection to the radio. Then there can't be any voltage across it. So, one improvement to this scheme is to run all the cables to a single point ground. All the cables, including those not on your diagram, such as power cables. If your radios are connected to a computer, all the cables connected to that, also. And if you want to follow the highest standards of lightning protection, anything conductive within four feet, even if not directly connected. With the cables traversing the attic where there are likely other electrical wiring, and possibly HVAC ducting, this may be difficult.

Route all those cables together so the loop area between them is minimized: that will help keep their potentials the same.

If it makes things easier, you can probably do without the ground wire to the radio unless you are operating some antenna with strong common-mode currents, like a single long wire. If you can eliminate the common-mode currents (for example, put a balun on a dipole) then a separate ground beyond what's already provided by the coax shield and the power cable adds no particular value.

Since the power cables need to be part of this single point ground, perhaps you can move the feedline to enter where the power service does. If not, you can add a branch circuit which has a surge protective device at the same ground where your feedline enters. Don't ground the neutral at this point: that would create a serious safety hazard. Instead, install a surge protective device with ground-neutral protection.

Either way, ideally the feedline and the power line from that grounding point follow the same path to minimize loop inductance, so that probably involves running a new branch circuit that follows the feedline path.

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