Here is how to correctly protect against lightning

Discussion in 'General Technical Questions and Answers' started by AI3V, Nov 6, 2019 at 6:13 PM.

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  1. K5EMG

    K5EMG XML Subscriber QRZ Page

    Well if calling someone stupid helps in avoiding a deadly mistake, then welcome. I don’t care about the messenger, but the message, and he’s right on this issue.
  2. WR2E

    WR2E Ham Member QRZ Page

    That's a fine thought, and if it works for you then great...

    but if he's going for a 'teachable moment', well, a condescending teacher that calls his 'students' stupid is not a good teacher. If the guy would lighten up a bit and lose the ego he'd be much more effective in getting his point across.
    W4PG likes this.
  3. KF5LJW

    KF5LJW Ham Member QRZ Page

    You are full of it. Extremely simple to do. Either you do not see what is going on, or you do not understand parallel circuit laws. Which is it I am giving you a way out, or rope.

    You are going to see part 2 which shows you have to remove all the loops leaving a SPG you do not understand. Look I am trying to help you and other hams. I do this professionally all to code for 40 years. Every commercial operator and wireless carrier does exactly what I am showing you. It is your problem and loss if you do not understand simple parallel circuit laws.

    Shucks why wait to embarrass you and prove it can be done real easily with some planning and understanding of the subject.

    Last edited: Nov 8, 2019 at 6:25 PM
  4. KV6O

    KV6O Ham Member QRZ Page

    Not sure why you think this. If you just follow the National Electric Code, Article 810 lays it out for you. This is the bare minimum you must do, there is more, but if some hams on here would just do this, their situation would be greatly improved.

    A mountain top site will take this a lot further out of necessity and the likelihood of many direct/nearby strikes. Your average house isn't subject to this. Disconnecting your feedlines everytime you turn off your radio isn't a listed option in the NEC. You can, but you still must comply with the code for your area. And honestly, you're more likely to get injured disconnecting your feedline outside in the dark with ice/snow etc. Just do it right, it's not that hard.
    Last edited: Nov 8, 2019 at 6:47 PM
  5. KF5LJW

    KF5LJW Ham Member QRZ Page

    Thank you for your support. You do know I am a Moderator on Mike's Forum right. I moderate the Ground and Bonding topics. Unlike here on a DIY forum, Mike Holts Forum is for professionals in the trade. On professional forums incorrect or dangerous recommendations are not tolerated. They will be corrected, edited, or deleted, and if a user continues giving bad advice is banned permanently.

    Everyone click that link as it clearly demonstrates SPG. See the Inter-System Bonding Bar under the electric meter. All services: CATV, TELCO, SATV, and Transmitting Coax all get bonded to a single point. Once the conductors go inside never see or come close to ground, thus isolated from outside.

    It is not hard and summed up this way. You Bond Everything outside below grade together and call it a Ground Electrode System. That includes ground rods, ground rings, water pipes, ufer foundation, water well, metal plates or tanks underground. All of it bonded together to make a Common Ground Electrode System as required by code.

    Then you bond everything together above ground.

    Last step is bond the two halves together at one Single Point. Code requires it W7ARK. Does not sound like your home was built to code or poorly laid out putting you and your family at risk. Might want to get that fixed.
    Last edited: Nov 8, 2019 at 6:54 PM
  6. N0TZU

    N0TZU Platinum Subscriber Platinum Subscriber QRZ Page

    I think that a large part of the confusion and disagreements involve the definition of a single point ground and where it applies.

    Looking at Dereck’s diagram above, there is a single ground for the RF Toys (the buss) and they are not in any loop. This means no lightning current will flow through them, great.

    But, there are multiple ground rods in the rest of the system, bonded together, with some loops in between. Clearly this is not a single point ground (single earth connection). Yet, it’s the correct way to connect all those items. Lightning current can flow between them, as intended, but will not damage any equipment. A bit confusing.
  7. K9STH

    K9STH Platinum Subscriber Volunteer Moderator Platinum Subscriber QRZ Page

    I will add my $2.00 (2-cents adjusted for inflation) to this discussion.

    Having been a telecommunications consultant for several decades with a couple of my specialties being lightning protection and grounding, I do have some opinions concerning this topic. My grounding methods have been adopted by various entities including several television transmitter manufacturers and the United States Navy War College. However, to use an old adage, there are more ways to skin a cat! There definitely are several different methods to achieve an excellent lightning protection system and I do not claim that "my way" is the "only way" to achieve such a system.

    My concept of a "single point ground" is to get all grounds, including all of the grounding electrodes, as near to the same electrical (voltage, etc.) level as possible with the reference point, according to NFPA NEC (National Electrical Code), being the grounding electrode for the AC mains entry point to the building. In theory, this means that every grounding electrode, every piece of equipment, and so forth, will be exactly the same. Of course, in the "real world", this is a practical impossibility. No matter how large the conductor between each item, there will be resistance and that means a different voltage. The whole idea is to get this voltage differential to the minimum possible level.

    NFPA NEC requires that the shield of every coaxial cable entering a structure be connected directly to ground. There are several reasons for this and all of those reasons are based on sound principles. This grounding electrode is required to be connected to the AC mains grounding electrode as are all other grounding electrodes in the system.

    Where a tower or mast is involved, the coaxial cable shield should be connected directly to that structure at the point nearest to the top (near the antenna) as possible and directly to that structure near the bottom at the point where the cable leaves the structure to enter the building. Then, another ground connection at the point where the cable actually enters the building (etc.). Where taller structures are involved, intermediate connections between the structure and the coaxial cable shield are recommended with a spacing of between 75-feet and 100-feet considered adequate.

    Good lightning protection grounds are seldom good r.f. grounds and good r.f. grounds are seldom good lightning protection grounds. However, both grounding systems do need to be connected together. In general, solid ground rods from 8-feet to 10-feet long are used for lightning protection. However, for r.f. grounds any rod over around 5-feet long is wasted. Where r.f. is concerned, over 90% of the effective ground occurs in the 1st 5-feet of the length of the rod.

    The "rule of thumb" for the spacing of ground rods is "twice the length of the rods". This is a reasonable figure. However, experimentation has shown that 2.4 times the length of the rods produces the maximum effective ground. Therefore, for 8-foot ground rods spacing them just over 19-feet apart, and for 10-foot ground rods spacing them 24-feet apart, produces the best effective ground. For r.f. grounding using 5-foot ground rods, spacing the rods 12-feet apart results in the best ground.

    For r.f. grounding using "chemical" ground rods usually work much better than solid ground rods. Such can be constructed from "hard drawn" copper pipe and then, after the rod is driven into the ground, filled with rock salt ("ice cream" salt). A diagram of how to make such appears on the last page of the document available at Grounding primer 3.pdf?ver=1570751570546

    Towers must have each leg connected to a separate ground rod and those rods connected to each other in a "ring" configuration. Then, those rods need to be connected to the remainder of the ground system.

    I am definitely a proponent of installing dissipation devices to greatly reduce the chances of taking a direct lightning strike. There are those "experts" who say that such are "snake oil". However, my professional experience is that they definitely work. In fact, at least when the Comanche Peak Nuclear Steam Electric Station was constructed, the Nuclear Regulatory Commission required that all towers, plus the containment buildings, have dissipation devices installed.

    Commercial dissipation devices are available from several different sources. However, they are pretty expensive. Fortunately, an amateur radio operator can build, or adapt, suitable devices at very economical levels. Building your own diagrams are found at the URL listed above or, much easier, stainless steel chimney cleaning brushes (available at home improvement centers) work very well as dissipation devices.

    The whole idea behind dissipation devices is to relieve the charge that builds up on the tower, or mast, before a "feeler" ("leader", etc.) is formed. Remember, a lightning strike starts from the ground and NOT from the sky. When the "feeler" gets long enough, it is met by the main charge coming from the sky. Basically, no "feeler", no lightning strike. Of course, there is nothing now known to man that can absolutely prevent a direct lightning strike. But, it is possible to reduce the chances of a "feeler" being formed and that reduces the chances of taking a direct strike.

    Horizontal antennas are much less likely to take a direct lightning strike especially when compared with a vertical antenna. This includes antennas from wires to Yagis.

    Commercial tower installations are, when proper grounding techniques are installed, capable of taking direct lightning strikes with a minimum, usually none, of damage to the equipment. With installation of dissipation devices the chances of taking a direct strike are greatly reduced. My professional experience with towers that were taking multiple strikes each year is that the strikes dropped to absolutely zero after the devices were installed. Of course, there is always the possibility that the acquired charge will overcome the ability of the dissipation devices to discharge this acquisition. But, having the devices installed definitely considerably reduce this possibility.

    Unfortunately, I have seen numerous grounding systems, installed by supposedly professional sources, that were just plain wrong! The installations were definitely "pretty" but were also definitely very inefficient. Frankly, good grounds are usually not pretty! Right angles in the grounding conductors are to be avoided as is a reversal in direction. Both things can result in a lightning strike actually leaving the conductor and going elsewhere.

    Lightning arrestors, when installed in coaxial cable lines, primarily get the coaxial cable shield grounded and there are other methods that achieve such at a considerably lower cost. Again, there are also lower cost methods of discharging static electricity imposed on the feed line. There is nothing wrong with installing arrestors but there are cheaper ways of doing the same thing.

    It is possible to take things from different grounding system recommendations to use in any particular system. My "feelings" are not hurt when some of my recommendations are taken while other things are not.

    Glen, K9STH
    K0UO and W4PG like this.
  8. KF5LJW

    KF5LJW Ham Member QRZ Page

    Thanks but hold the buss there for a moment. You got most of that correct, but there is a SPG. Stop and think for a second what a SPG definition really is. Again it is very simple. It is a Reference Point we call o-volt reference point. We can reference a SPG to a ham sandwich and it will work perfectly and immune to lightning because there is no connection top dirt. So lets define a Single Point Ground: A point in which is isolated and No Ground Appears beyond the Dmarc Point. So when any conductors is bonded outside before entering never sees any ground beyond that point All the ground wires from the point of entrance is an Open Circuit. No current can flow in the Single Point Ground Plane. It does not matter what happens before that point as any lop before that has no effect and our equipment never news or feels any disturbance.

    Otherwise you are spot on. We dont care what currents are flowing on the outside world. We cannot control what happens outside but we can control what happens inside. So we do not give the outside world a path through our kingdom, we route it around us outside and keep it there as designed and intended. FWIW there are good loops, and you fix bad loops with good loops like I have done.

    There are a lot of good Ground Loops. Example high rise building are built with steel frame structure with more Ground Loops than you can count going all the way to the roof. In a high rise building you use the steel frame of the building as Ground for your transformers. Transformers have to be installed every third floor to prevent horizontal ground rise potential from being felt. A transformer removes all common mode currents and establishes a new Ground Reference. They bond the transformer center tap to the building steel as their ground electrode connection. So now 0 volt reference on the top floor is on the top floor with the transformer. If you did not use building steel located on the floor serviced and rather ran a cable down to a ground rod would get someone killed during a thunderstorm. When lightning strikes, generates a huge pulse wave of current which requires extreme voltages into the 100's thousand of volts. So when lightning strikes a high rise building forms a VOLTAGE DIVIDER along the vertical length of the building. At the top say 100,000 on a 100 story building. You are on the 50th floor half way up so the voltage on the 50th floor is 50,000 volts above ground voltage. If you used a wire as the ground would be a Ground Level Potential of 0-volt reference. On the 5oth floor the building steel is at 50,000 volt higher voltage. So you are touching the microwave, on the phone, something that connects you to AC Ground coming from the basement and lightning strikes. You are between building steel and AC ground down stairs 500 feet away. You are a crispy critter. Its already happened long long ago and the fix is simple. A simple loop, a good loop the NEC requires you to make. You would be required to bond the Center tap of the Transformer to nearest Building Steel. You now have a SPG referenced to the 50th floor. Now when lightning strikes nothing happens, all the current is Shunted around you with no potential differences within reach.

    So yes you can easily implement SPG. You gotta know the bad loops from the good loops. Never ever put any equipment, I mean any electrical equipment in a Ground Loop. Fix it by Shunting with a Good Loop to make Single Point connection to the loop. No earth grounds beyond that point.
  9. KV6O

    KV6O Ham Member QRZ Page

    Glen -

    Here's a tower near a site I have equipment at with the "bottle brush" dissipation devices:


    None of the sites I manage have them, and we seem to do just fine. I am an R56 stickler, however... :cool:
  10. K9STH

    K9STH Platinum Subscriber Volunteer Moderator Platinum Subscriber QRZ Page


    My philosophy is to install the best grounding system possible to minimize damage from a lightning strike. Then, install dissipation devices to reduce the chances of even taking a lightning strike.

    There are companies that guarantee that you will never take a direct strike if you install their dissipation devices. Then, if you do happen to take a strike they claim that the devices were not properly installed! As I said before, there is nothing known, at this time, that can absolutely eliminate the chances of taking a direct strike. Reduce: Yes. Eliminate all possibilities: No.

    Glen, K9STH

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