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Lightning and Grounding

from Michael S. Higgins, K6AER on April 2, 2018
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"Editor's Note: Due to the popularity of some of eHam's older articles, many of which you may not have read, the eHam.net team has decided to rerun some of the best articles that we have received since eHam's inception. These articles will be reprinted to add to the quality of eHam's content and in a show of appreciation to the authors of these articles." This article was originally published on: 03/30/2006





Lightning and Grounding

Well it is that time of the year when postings turn to grounding and lighting protection.

So much information has been posted on lightning protection in this fourm you could spend hours going through all the information listed and I would recommend doing so. Use the search engine in eHam and by all means forget the naysayers of grounding. Go to the PolyPhaser site and read their tutorials on lightning protection. Go to Lyncole, Hagar and ICE (Industrial Communications Engineers) and read their tutorials on grounding. There is no short cut to lighting protection. Your whole station and home needs to be addressed as a complete solution. Now if you live in the Northwest you can skip the rest of this article for your chances are very slim you would even see a thunderstorm. For the rest of the county this is an aspect of the hobby we have to deal with. This article is a reader's digest version of what must be done for surge protection and I hope it start you thinking about your home and station.

Every other year on average my station gets hit by lightning. This was not a problem when I lived in LA; I had a greater chance of being hit by stray bullets. I live in a very high lightning prone area called the Palmer divide in Colorado. June through August we have thunder storms every day with up to 40,000 strikes a day on average during those months. I am on my 3rd GP-9 antenna at the top of the tower. When a storm has gone by and I find what's left of a GP-9 in toasted shards all over the ranch, it doesn't take a rocket scientist to know what happened. I have lost no base station equipment to a lightning strikes but I have spent considerable time putting in proper grounding and surge protection on my station. As for the tower top fiberglass omni sticks, they're sacrificial and that just the cost of doing business where I live.

Proper grounding and surge protection works and works very well. The key is setting up low resistance grounding and the proper installation of grounding material. Disconnecting you equipment and putting it into a Faraday Shield box will work well but if you live in an area like my QTH you would be off the air for 3-4 months every year. Some hams like my self have more than one radio and going this route would mean my hobby is station assembly. I can't speak for most hams but after doing that a few times it looses its novelty.

The cell phone industry looses less then 20 sites a year to lightning. There are approximately 500,000 sites between Verizon, Nextel, Cingular, Sprint and others. Generally it is because the DSL line is struck and not the radio equipment. In the cell phone industry we ground at the top of the tower, base of the tower and where the cable goes into the facility. The facility has a ground halo inside and the all equipment is grounded to NEC code. Surge protectors are connected for all incoming and outgoing lines at the ground demarcation point. Site ground resistance is generally below 3 ohms. Four 20 foot deep ground rods is a grounding minimum. The AC entry panel has surge protectors (95% of all lightning damage comes in through the AC panel) and most importantly all the facility grounding is bonded together.

Power lines take by far the greatest hits and the pole flash-over-rods pass any surges below 10,000 volts. That still leaves a lot voltage coming down the power line. The primary and secondary portion of the pole transformer can arc over and your home is next in line. Your home AC panel should have a surge protectors connected to the panel. You worry about your ham equipment but what about your expensive entertainment and appliances not to mention the possibility of fire. You can protect your home and panel for under $100. Intermatic makes the Panel Gard model number IG1240RC surge protector for $60 not including the two additional circuit breakers. This unit has LED's to indicate the units status and wither you have taken a power surge. Installation is just three wires into the panel.

Did I mention lightning rods for the roof? Lightning is fickle and might miss your gorgeous tower and strike through the roof to the electrical wiring in the ceiling. The ground return in your home wiring connects to the master ground in your AC panel. Remember a lighting discharge is looking for the lowest impedance path to ground, i.e. earth. If your live in a highly lightning prone areas like Colorado, Florida and much of the mid west, lighting rods are a good investment. National Lightning Protection in Denver makes all the necessary material to install your lightning rod system. Their web site is a wealth of information.

In my own station, all grounding is bonded with a number “0” solid copper bonding wire. My ground resistance is less than 3 ohms. I have several deep (20ft. by 2 inch) ground rods for the tower, AC panel and shack location. I also have a surface ground field of 21 8ft. ground rods spaced 16 feet apart, spread out in radials from the tower. At the base of the tower is a lightning/surge protection panel for the coax, rotor cables and stepper motors on the beam. For the surge protection box I use 2 inch wide copper strap. Copper strap has much lower impedance than copper wire and much of lightning's energy is in the RF spectrum.

Coaxes are grounded at the top of the tower as well as the base. The AC panel has a commercial lightning protection panel to take care of incoming AC surges. The whole station is run on a pair of 3000 watt APC UPS systems to isolate the AC main from the equipment for minor surges. At the station, coaxes are terminated at a pair of grounded Alpha Delta coax switches and during storms the coax switches are in the grounded COM position. All equipment is grounded to a master ground buss bar on the back of the operating station. The master AC feed to the station has a commercial disconnect in the shack. I know many of you will this is excessive but proof is in the pudding. I have suffered no equipment losses due to lightning strikes.

Remember if the cell phone, radio, public service and computer industry disconnected equipment for every summer storm, you would not have communications coverage or internet service for five months every year. The communication industry is connected 24/7. As a result, proper lightning/surge protection with good grounding works. Is it 100 % full proof…NO, but it is infinitely more effective than sticking you head in the sand with denial. You don't plan on getting into an accident but you have car insurance. Lightning surge protection is an insurance policy and another tool in your station/home safety plan.

Many hams have their station and personal electronics insured but collecting and replacing equipment is tedious and would it not be easier to prevent the damage in the first place. Due the proper diligence and you'll sleep better at night.

Member Comments:
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Lightning and Grounding Reply
by KA4KOE on April 2, 2018 Mail this to a friend!
The kind reader is encouraged to consult NFPA 780, Lightning Protection Code, and on-line information distributed by LPI, the Lightning Protection Institute.

An improperly installed system is sometimes worse than the lack thereof.

Fleep
 
RE: Lightning and Grounding Reply
by K6AER on April 2, 2018 Mail this to a friend!
" An improperly installed system is sometimes worse than the lack thereof."

That is going to be hard to prove without an exact A/B test comparison.

I suppose you could theorize if the tower was grounded and the surge came in via the line feed to the home you equipment would be the fuse as the surge traveled from the unprotected panel through the ham equipment to the tower ground.

Now if the tower was ungrounded would the ham equipment be saved…probably not. Ground returns exist in the wall plug that are sufficient to cause a ground return to earth any way. Still the only effective way to mitigate surge potential is to do everything necessary. AC line feeds and proper station and antenna grounding need to be completed.
 
RE: Lightning and Grounding Reply
by KA4KOE on April 2, 2018 Mail this to a friend!
For instance, right angle sharp turns in grounding conductors carrying a lightning surge will encounter a high impedance. The surge will often side-flash "looking" for another path, often causing damage. Since lightning and grounding systems must be interconnected, improper installation is indeed documented to cause damage, at least from the point of view of those writing the codes and installation standards as well as insurance underwriters.

Dissimilar metal corrosion is another factor, ie aluminum/copper connections improperly joined, leading to failures in ground paths.

Here are a couple of links (there are many others):

http://lightning.org/consumer-alert-homeowners-warned-about-the-dangers-of-shoddy-lightning-protection-system-installations/

https://ecle.biz/wp-content/uploads/2015/01/Spring02ECENarticle.pdf

I agree that the comparison between "none" being better than "bad" is probably apocryphal. However, poor installations are likely to cause more problems than those they can are supposed to prevent.


 
RE: Lightning and Grounding Reply
by K6AER on April 2, 2018 Mail this to a friend!
“For instance, right angle sharp turns in grounding conductors carrying a lightning surge will encounter a high impedance. The surge will often side-flash "looking" for another path, often causing damage. Since lightning and grounding systems must be interconnected, improper installation is indeed documented to cause damage, at least from the point of view of those writing the codes and installation standards as well as insurance underwriters.”

Being 95% lightning RF energy is below 10 MHz how much inductance would a right angle turn on a number 6 copper present. The inductance would have effect above 1 GHz but not down below 100 MHz.

I attended the HAGAR lightning seminar for a week and that scenario came up. They laughed and said the reason the arc took place is there was probably a ground near by.

I have also heard that a direct strike on a car will vaporize the auto. Never seen a picture as proof. My airplane has been struck several times and it is still intact.
 
Lightning and Grounding Reply
by AC5WO on April 2, 2018 Mail this to a friend!
The most important concept of protecting electronic circuits from lighting damage is to keep the voltage difference between the different conductors entering the protected area low enough to avoid damage while having conductors large enough to survive the surge current. You want a common ground with short, wide conductors to minimize inductance with a common ground for all lightning protection hardware. It's physics, not magic, with the voltage over time across the conductor inductance = L (di/dt). That common ground is going to change potential with a lightning strike, but the electronic circuits survive as long as everything stays close enough to the same potential. I have some doubts about the cost effectiveness of 20 ft long ground rods, I'd probably install a larger number of 8 ft long ground rods connected by fat conductors, but soil resistance in Colorado may be different than what I'm used to.
 
RE: Lightning and Grounding Reply
by N8EKT on April 2, 2018 Mail this to a friend!
Are you still replacing GP9s or have you found something that doesn't explode? lol
 
RE: Lightning and Grounding Reply
by AF7ON on April 2, 2018 Mail this to a friend!
I did a theoretical and experimental study some years ago to try and put the myth of inductance at right-angle bends in lightning conductors to rest. It's pretty easy to demonstrate that the inductance is insignificant and although this "fact" was included in many international codes, as evidence proved its mythological origin, it's been gradually dropped until only the US Code still has it!

Many vehicles are struck by lightning, the results typically (but not always) being one or more blown tires and damage to electronic components. Modern cars will often die as the various microprocessors get fried by the induced surges in the wiring. I have seen more than one shattered windshield too. If the car doesn't crash as a result of the lightning strike (this does happen), serious injuries are rare. Motorcyclists are at more serious risk.

Mike
 
Lightning and Grounding Reply
by K5END on April 3, 2018 Mail this to a friend!
Excellent article. Thank you.
.
It may be worth emphasizing the spectrum width of lightning is very broad because of the short time duration of lightning pulses* (most lightning strikes are actually multiple strikes in rapid succession, which with high winds create the appearance of ribbon lightning.)

Polyphasers are necessary as the author mentioned.

*The bandwidth of a signal can be represented with the Fourier transform of the signal. I would think the Dirac delta function, a defined theoretical pulse infinitely high and infinitely brief pulse, is a somewhat fair comparison of a single strike. Of interest, this is why a lightning strike can be heard all across the AM broadcast band. It’s on the FM band too, but not audible.

Yes, sharp angles are bad for ground conductors. Any bend increases inductance which increases impedance.
 
Lightning and Grounding Reply
by K5END on April 3, 2018 Mail this to a friend!
A metal body car with a metal roof with the doors closed is a good emergency shelter from lightning, but you must keep your entire body inside the car and it’s a good idea to keep your hands off the dashboard, etc.
It’s a fair Faraday cage.
In lab experiments with high voltage simulating lightning, it arcs from the car axle to ground.
 
RE: Lightning and Grounding Reply
by K2JVI on April 4, 2018 Mail this to a friend!
I too have an extensive grounding and bonding system at my QTH(Quiz-what's the difference between grounding and bonding? answer to follow). Anyway I do have several ground rods around a portion of my house, and a few ground rods extending about 30' from my house in one direction. Also for every rooftop antenna(2meter,TV, satellite dish) I provide a straight as possible run on #6 copper from the antenna mast/hardware to its own ground rod which is BONDEDD to the rest of the grounding network, which is BONDED to my main electrical ground. So I have a 30' ground ring at the footing level of my addition, and a ring that is formed by several ground rods for the various roof antennas and the 30 straight run away from my house, again all bonded together and the entire network is bonded to the main electrical ground.Hope you caught the answer to the quiz question. In a nutshell-grounding is the active connection to a grounding electrode in contact with the earth,while bonding is the interconnection between grounding elements OR other metallic items(IE chassis,racks etc) to provide a low resistance connection...
73's
Bob
 
Great article. Thank you, Michael! Reply
by K6BRN on April 4, 2018 Mail this to a friend!
NT
 
Lightning and Grounding Reply
by KD8NGE on April 5, 2018 Mail this to a friend!
To quote the late Paul Harvey, "I am listening with both eyes!"
My station was hit by lightning, my lightning precautions were insufficient and I paid the price.
Ouch.
My piggy bank still hates me.
No fire but plenty of equipment loss.
Part of my personal plan was a low height antenna, no part was more than 8 feet off the ground ... Thor's hammer hit it anyway.
Local TV news station showed a viewer's vid of a lightning strike on a moving car ... the stroke ignored multiple spun-aluminum street lamp posts and hit the automobile, further illustrating that lightning hits where it will, and lightning protection -- effective lightning protection! -- is a very good idea!
 
Lightning and Grounding Reply
by VK2LEE on April 6, 2018 Mail this to a friend!
My Tower was hit about 8 years ago burning out all My new coaxial cable and causing some damage to My Yagis and antenna switches as the only GROUND I had at that time was inside My shack... NOT GOOD.... Luckily I had all of My equipment un-connected... I now have Ground rods outside connected to My coaxial cables before they go inside the house. I also have ground rods connected to My Tower. Every thing that was damaged was replaced by My insurance company, apart from taking the old Yagis off My tower and assembling My new yagis. I still disconnect all My coaxial cables when there is any lightning about. A VK Ham told Me recently He had been hit by lightning taking all His radio gear out plus other items plugged into the electrical sockets. I haven't thought about lightning coming thru the mains power sockets although I do use Surge protectors in most of My power sockets. Hopefully the new circuit breakers I have would trip before damage???
Lee VK2LEE
 
RE: Lightning and Grounding Reply
by N6JSX on April 11, 2018 Mail this to a friend!
What really makes you feel good about the hours of effort you GAVE eHAM is when they slight you over their favorite writers on a given topic.

What eHAM could do is add links at the end of the selected article to other relevant notable eHAM prior articles to give the reader a balance and more information to consider on that topic.

How about going back to 12/2000, and re-post:

http://www.eham.net/articles/1603

From the Ground UP
 
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