[bars] Ground tester?

[William Smith]

Hi Tom,

Thanks for your reply, it's not clear where the lightning strike entered the house:

A) The power lines are all underground, so that's unlikely.

B) The VHF Radio antenna has a good (Polyphaser) lightning arrester on an 8-foot Shakespeare boat radio antenna at the roofline, and the radio is still working fine.

C) The internet node did fail, but it also has a lightning arrester on it, and they are notoriously fragile, and the RJ45 connector was all rusted(?), so they had to replace it, not sure if that just looked rusted because it was blown up by lightning, or if exposure to the hurricane-driven salt spray actually corroded it.

D) The house has lighting rods and big braided wire and big ground rods at each corner, but no-one is sure how they are connected.

The main first-floor electric panel (where the basement network rack is fed from) has a surge supressor, and the breaker for the rack was tripped.  It;s really unlikely that the lightning strike came in from the power lines, as they are all underground.

I've found a number of wiring anomalies, and I'd like to know if there's a way of using a ground tester to see if things really are grounded, and to get an idea of how good a ground (for the purposes of the lightning arresters) any and all of those grounds might be.

I've seen more "how to" discussions on lightning and RF grounding, but none on testing the resultant system to determine if it really does what it's supposed to.

Does that shed any light on my question?

73, Willie N1JBJ

> On Nov 6, 2022, at 10:43 AM, Tom Walsh <k1tw at comcast.net> wrote:
> 
> Willie,
> 
> I can't advise you on the test equipment but reading your message it is not clear to me how the lightning damaged the equipment or
> even entered the premise.  Was it via the electrical service, internet service, or radio antennas?
> 
> You mention internet connectivity parts being damaged.  Was the VHF Radio damaged too. What kind of antennas are used?
> 
> Perhaps the first consideration is whether the electric service has a surge protector  installed at the entry point?  That is
> something I recommend strongly.  That should help protect the internet and home entertainment gear (and radios too).
> 
> Tom
> 
> 
> 
> -----Original Message-----
> From: bars <bars-bounces at w1hh.org> On Behalf Of William Smith
> Sent: Friday, November 4, 2022 7:16 AM
> To: BARS Reflector <bars at w1hh.org>
> Cc: William Smith <wpns at geekho.com>
> Subject: [bars] Ground tester?
> 
> One of my neighbors in the Turks & Caicos appears to have taken a lightning strike which blew up a few thousand dollars worth of
> internet connectivity parts.
> 
> I'm in discussions with his electrician about what kinds of ground are appropriate for his VHF radio and Ethernet lightning
> arresters (big wires, short runs, no bends, loops, or coils, directly to the nearest ground), and I'm not sure he's even interested
> in making sense of the wiring mess that's extant, but I thought it might be instructive to use a ground tester (Earth Resistance
> Tester, Megger, etc) to see if the various grounds are even connected, much less good RF grounds.
> 
> Has anyone used something like https://www.amazon.com/Best-Sellers-Ground-Resistance-Meters/zgbs/industrial/5011685011 to test
> grounds, are they useful, and can they tell a good RF ground (as above) from a coil of wire that's electrically connected to ground?
> They seem to range in price from a few hundred to a few thousand, so I've sent out feelers about renting or borrowing one.
> 
> If this is the wrrong tool for measuring RF Ground Impedance, what is the right tool (or procedure) for doing so?
> 
> Thanks!
> 
> 73, Willie N1JBJ
> 
> 
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