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Please forgive the naive question, as I've been away from the hobby for too long, but want to make sure I do this right.

We just added an addition to our house, and I lost my usual mounting place for my X200a. I've never had this antenna mast connected to a ground rod for lightning protection before, but I'm wondering if in this new location, I should...

I'm wondering this because of a few reasons:

  1. The X200a will be several feet lower than it was before (rather than at the apex of my roof, it will be at the bottom of the soffit line right by the gutter, mounted off of a satellite radio mast).

  2. I'm in a very suburban area, near a water tower, and another ham down the street who has many more antennas on his roof, much higher than mine.

  3. Aside from #1 above (below the apex of the roof), we have several trees on our property which are 30-50 feet taller than the house. Yes, trees are not made of a conductive material, I understand that. Just another point of emphasis.

Yes, I know, lightning can strike anywhere and the "you should always ground everything to multiple ground stakes," etc., but I'm hoping for a productive, realistic answer from here as opposed to what I'd get on other ham forums.

Given the above - does the X200a really need to be grounded for lightning protection?

This is a duplicate question of...

No, it's not a duplicate. I've looked. I know how to properly ground my equipment. I'm asking if and why I should ground my equipment given the above conditions.

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  • $\begingroup$ Possible duplicate of How can I protect equipment against a lightning strike? $\endgroup$ – Phil Frost - W8II May 24 '16 at 16:25
  • $\begingroup$ Don't arbitrarily add ground rods: you'll likely make things worse. Don't think a strike must directly hit your antenna to damage equipment: the powerlines, or the ground anywhere in your neighborhood can be just as bad. See How can I protect equipment against a lightning strike? $\endgroup$ – Phil Frost - W8II May 24 '16 at 16:29
  • $\begingroup$ @PhilFrost This is not a duplicate. I'm not asking how - I'm asking if and why? $\endgroup$ – CDub May 24 '16 at 19:46
  • $\begingroup$ @PhilFrost Okay, so a better option than running ground ribbon to an earth ground from the antenna mast would be to unplug everything during a storm? I have everything on surge protectors, but I could unplug it if that's the best option. $\endgroup$ – CDub May 24 '16 at 19:47
  • $\begingroup$ You assert that you know how to properly ground your equipment, but I don't think you do, if by "properly" you mean in such a way that your equipment won't be fried by a strike in your neighborhood. Really, go read the other question, and see if you still need to ask this one. The answer to "if" is "yes", and "why" is already addressed in the other question. $\endgroup$ – Phil Frost - W8II May 25 '16 at 18:18
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You question seems to boil down to this: "Do I need to be concerned about lightning protection, even though my antenna isn't very high relative to its surroundings?"

The answer is yes. In fact you need to worry about lighting protection even if you have no antenna at all.

Say you have this:

schematic

simulate this circuit – Schematic created using CircuitLab

You have your radios and whatever connected to a great big ground rod near the station. Maybe you attach the ground to the chassis, or maybe it's part of the ground for your antennas. Maybe you even make all the connections with heavy copper strap. Maybe you even have a mesh mat under the floor and the desk. This station is really grounded.

And there isn't even an antenna. A lightning strike directly on your station is quite unlikely.

Safe, right? No. We have failed to model the finite conductivity of the soil between the two ground rods. The situation is more like this:

schematic

simulate this circuit

Soil conducts electricity, but not very well, represented by the resistors between the two grounds. Now when lightning strikes nearby, maybe on the ground, maybe a tree, or maybe it hits the power lines, all that charge transferred by the strike needs to go somewhere.

At the strike point, and at the instant the strike occurred, there's an excess of electric charge that was put there by the strike. Like charges repel, and so all this electric charge flies away from the strike point, until it's more or less evenly distributed over the surface of the Earth.

Where does it flow? Like all current, wherever it can. The lower the impedance of some path, the more the current will flow there. The soil is pretty resistive, and copper wires that run through your equipment is not. So you are providing the strike current a shortcut through the relatively poor soil conductor which goes through your equipment, probably resulting in damage.

Lightning arrestors won't help you at all with this particular problem. They are essentially spark gaps. Consider, the strike current is driven by a force strong enough to create an arc between the ground and the clouds. A little piece of metal isn't going to stop the current that needs to get from point A to point B.

This is why you must consider lightning protection, no matter what your antenna installation, or indeed, even if you have no antenna at all. You must make sure there is no path between two points in the ground which flows through your equipment. "Properly" grounding your antenna is likely to do exactly this.

See How can I protect equipment against a lightning strike? for a more detailed explanation of how to ground your station in such a way that lightning damage is unlikely.

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  • $\begingroup$ Thanks for the write up. What if I don't have my station grounded at all? So the "'proper' station ground" doesn't exist - the only point of entry would be through the house electrical service ground, right? $\endgroup$ – CDub May 27 '16 at 18:52
  • $\begingroup$ @CDub I wouldn't say a station that's plugged in is "not grounded". It's grounded through the power cable, and if you look by your electric meter there's a ground rod there (code requires it in the US, anyway). Anyway, don't think about a "point of entry" for lightning. Think about the entire circuit where the current flows. $\endgroup$ – Phil Frost - W8II May 31 '16 at 12:26
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Welcome back to ham radio, and to ham.stackexchange.com! I don't think your question is naïve at all. It is however very similar to a question that we just debated recently. Check out that discussion, and especially the earlier question How can I protect equipment against a lightning strike?

To answer your specific question, in my personal opinion having your antenna be lower down on the roof than it was before, and close to some tall trees, a water tower, and another ham's tall antennas, doesn't count for much protection. I think a good lightning arrestor connected to a good ground system would serve you much better, without costing too much. But it's your equipment and your health at stake, so do as you see fit. 73!

P.S. My dad had a station in the Chicago suburbs for 21 years. He didn't bother with much of a lightning protection system; his shack suffered lightning damage three times from nearby hits. He had a 40-foot tower though.

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  • $\begingroup$ Thanks for the awesome (and non-sarcastic, straightforward :-)) reply! I guess I just don't understand physics and electricity - lightning looks for the path of least resistance, right? If so, why is my antenna to 50+ feet of coax, to a rig, to my power supply, to my house electrical, to the house ground so vulnerable? $\endgroup$ – CDub May 24 '16 at 2:04
  • $\begingroup$ lighting goes via least resistance, ok. But we dont know where in air nature makes "low resistance channel" until lighting strikes. Look at cited here other threads, good info $\endgroup$ – Jacek Cz May 24 '16 at 8:46
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    $\begingroup$ @CDub I think you're looking at the problem in a narrow way. You're thinking about influencing the path of a lightning stroke. Consider what would happen if lightning did hit one of those nearby trees, and suddenly there's a massive electric field coupling thousands of volts into your antenna and coax, even though your station wasn't hit directly. The good news is that reasonable precautions can greatly reduce or eliminate damage from a nearby strike. $\endgroup$ – rclocher3 May 24 '16 at 15:30
  • $\begingroup$ So, by that logic, the water tower and my neighbor... The tree in the back yard... Anything in the area, really, would be in play for this problem, right? If there's a massive electric field generated near by coupling thousands of volts on anything that conducts electricity, pretty much every electrical component would be fried regardless of connections or not, correct? $\endgroup$ – CDub May 24 '16 at 19:49
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    $\begingroup$ @CDub It sounds like you're resisting the idea of a lightning arrestor. Most hams probably don't bother with them, honestly. But that's not good engineering, so most people on this site will say that you should have one. It would be interesting to see the results of a cost-benefit analysis to find out if spending the money is worth it, but I doubt such an analysis has ever been done. In the end the risk is yours and the money is yours, so you get to decide for yourself. $\endgroup$ – rclocher3 May 24 '16 at 20:21
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Polish professional antennas installation (police, firemen), antenna type 32812 similar in sizes to x200 are mounted like this (sorry, cant find with english description) odgromnik - arrestor odległość - distance długość - length

enter image description here

EDIT: I do not negate rest of discussion. Problem should be resolved in good, complex way - or not resolved all, i.e. problem of loop ground

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  • $\begingroup$ Hello Jacek and welcome to ham.stackexchange.com! Your picture is interesting, I don't think I've seen an antenna with a lightning rod attached to it. That must discourage a direct lightning hit. I wonder how the lightning rod changes the pattern or the impedance of the antenna? $\endgroup$ – rclocher3 May 24 '16 at 15:36
  • $\begingroup$ Agree, HAM way of thinking is full of care about every dB of signal. Maybe professional way is different? No-one from professional seller-installer have problem "oh no! 1.5dB lower!!!" Police, firemans units have limited service area $\endgroup$ – Jacek Cz May 24 '16 at 15:44
  • $\begingroup$ This is photo version, from firm selling in professional market dipol.com.pl/images/a074.jpg $\endgroup$ – Jacek Cz May 24 '16 at 15:49
  • $\begingroup$ I meet rule "distance > 0.5 lambda from metal mast is sufficient, 1 lambda happy", for pro freq 170MHz lamba (wave length) is .1.7m. Non-resonance distance probably is better??? $\endgroup$ – Jacek Cz May 24 '16 at 15:53

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