Antenna and lightning ?

[mackmobile43]

A few years back, maybe ten I was in the finishing stages of having my home re-roofed with one of those fly by night storm chasing roofing crews(see how big an idiot mack was then) so me and the crew foreman were standing in the car doorway of my garage when this rouge summer storm came up while the roofing crew( all non engrish speaking) were putting the finishing touches on the ridge line.

There was a few intense lightning strikes around so I told the foreman maybe he should have his crew stop work and come down until the storm passed and his response was "awww day is jus abut duns"< he was cajun.lol

Well about that time a bolt struck the north goal post of the local highschool football field 150 feet across the street and that bolt arched from there to an old tv antenna on my roof which was not connected with a wire, luckily no one got hit but the resulting bang really got their attention and you never saw so many ( all non engrish speaking) roofers leave that roof without the use of a ladder.lol

I felt the hair stand on ends all over my body and felt like I had been hit in the chest with a good stiff punch but it wasn't due to the electrical portion of the strike but a concussion strike from the thunders result.

 

[RatsoW8]

Oh it was an amazing show here last night. I stoood outside and watched for about 20 minutes or so. All I saw was cloud to cloud discharges and it was non stop and very intense...I kept thinking about the new version of War of The Worlds...

 

[TonyV225]

The brain can also take bad hits from a close call or sideflash. Your body runs on electrical impulses from the brain and a closecall as mentioned can be catotrophic aswell depending on the indavididuals involved healthwise. Are bodies are like machines and not all built exact so you never know. Ive seen lightning hit within a few hundred yards leaving showers of sparks ETC and let me tell ya if the sight dont get you the after sound will

Im glad this fella and his family had a good outcome instead of what could have been. I disconnect all 6 antenna feed lines along with rotar line but also have extra grounding on my tower as mentioned but still disconnect and coax and 8 pin rotar line is tucked away outside away from the house in a dry place along with internal equipment grounds being disconnected. Equipment should also be unplugged although I for one do not always do this and if lightning were to hit there is a 75% chance that it will feed up through the ground and cause havoc so I need to start remembering this as everyone should

 

[BOOTY MONSTER]

well , i got questions .... as usual :laugh:

if lightning strikes the antenna its toast . irregardless of grounding methods all the equipment still needs to be disconnected from the antenna and ground rods in the event of a storm . so , with the exception of reduced noise on some installs whats the benefit of the grounding ? since none of the equipment will be adequately protected even with extreme non commercial methods/equipment , it kinda seems like a futile effort .

 

[Robb]

If the hair on your body should raise up; then you are in a 'ground field'. A strike is imminent. Crouch down into a ball with only the ball of your feet supporting you; this way you make yourself a much smaller target. Either that; or get back into your car if it is very close by, as it will behave as a "Faraday's Cage" so long as you touch nothing inside the vehicle that is attached to the chassis.

A "Ground Field" will shift constantly; one moment it is there and the next it is gone if it doesn't receive an opposite charge (read "strike") from the cloud. If you are in the house, you might notice your hair raising up there - too. Just remember, that the antenna doesn't CAUSE the strike; but it becomes an attractive nuisance for a strike IF the ground field current should rise up close by . . .

 

[TonyV225]

Booty thats a a good question and alot of people ask this very same thing. I have seen grounding make know difference on radio operation as far as noise Standing Wave Ratial ETC and I have also seen grounding help these very same things as Ive also seen grounding cause problem with these things.

Its crazy and at times unexplaatory but it is what it is and we never know until we try and look at the outcome. As far as lightning I will say that if its your day its just that (YOUR DAY) and your not stopping it but merely trying to control it the best you can with the least damage aftermath as possible.

I know a guy here in Wisconsin about 45 minutes or so from me that was on his radio in his seperate radio shack built onto his garage away from the house and a day after he put his tower up he was on the radio he was sitting back listening and wham!! he felt it heard it and seen it and this fella just knew he said uhhh ooohhhh!! He went and looked and he was lucky because he was using one freshly installed groundrod along with some flat copper ground strap.

Lucky for him it worked nothing as ironic as it sounds was damaged!! All he said was the clamps that were bolted to the tower holding the groundstrap blew apart and the strap was disconnected. He said those bolts were laying by his neighbors garage they flew and hit the garage and againg no damage to beam or anything!!

He lives right on a lake with lakefront propert so it a haven for lightning I would imagine. I told him I bet that was your one chance to have everything survive because getting hit is like winning the lottery and to have no damage to anything is not even imagiable so as weird as it is I can bet it wouldnt be like that again should he take a hit again.

I am baffled on the fact there was absolutely no damage to beam or radio equipment and it was all plugged in and in use!! It all goes with rthe fact that lightning is the most unpredictable thing and there are absolutely no guarantees on its outcome. Ive had 2 sideflashes that took out phones and computers so surviving a direct hit is simply just nuts and unexplainable!!

 

[RatsoW8]

well , i got questions .... as usual :laugh:

if lightning strikes the antenna its toast . irregardless of grounding methods all the equipment still needs to be disconnected from the antenna and ground rods in the event of a storm . so , with the exception of reduced noise on some installs whats the benefit of the grounding ? since none of the equipment will be adequately protected even with extreme non commercial methods/equipment , it kinda seems like a futile effort .

Booty, The question is; how do you make an antenna and tower less of a target for lightning? By grounding it to earth potential and making it more likely target for a strike? One thing I didn't do with my tower was make it the tallest structure around me. There were trees and other objects close to me that were taller and at earth potential. It was actually the power pole behind my tower that got hit but some of the charge ran down the outside of my tower.

Lightning is a very powerful force and no fancy arrestor or gadget is going to stop thousands of ampres of current if your structure is the most inviting to a charged up cloud. It's a game of chance we all play with the metal lightning rods we put into the sky and call antennas... When the lightning starts my coax goes out the window.

 

[TonyV225]

DITTO With the out the window but I usually watch the radar daily and if I hear thunder then everything geets disconnected and outside it goes. The problem is that when my kids wake me up at 3 in the morning to tell me its lighning or starting to storm I find myseld panicing and taking coax out when it not the propper tim (WHILE ITS LIGHNING )

I often b!+ch about it or having to do it but I tell myself that Im the one that loves the hobby and nobody forces me to stay in it so if im gonna play its part of the rules to the game

 

[Robb]

well , i got questions .... as usual :laugh:

if lightning strikes the antenna its toast . irregardless of grounding methods all the equipment still needs to be disconnected from the antenna and ground rods in the event of a storm . so , with the exception of reduced noise on some installs whats the benefit of the grounding ? since none of the equipment will be adequately protected even with extreme non commercial methods/equipment , it kinda seems like a futile effort .

The antenna isn't necessarily 'toast'.
Having the system set up to allow for little to no resistance of massive current to flow to ground is the point. Keeping the potential damage to the building is the reason. If there is too much resistance to the flow of current; then the items inline will heat up and get destroyed.

I can see an Imax, Gain Master, or A99 explode due to the fact that the conductor is on the inside - in which case any water inside will turn instantly into steam.
Makes a great case for an all-aluminum antenna unless lightning isn't a problem in your area..

Towers are supposed to have 3 or 4 ground rods with large gage braided cable; aren't they? If so; then the intent is to move the current flow without resistance and away from the house. Where fire can become a lighting caused disaster. Keeping out any part of the lightning flow within the house is the responsibility of the radio operator - Ham or CBer . . .

AS for home water pipes and electrical systems; they can be a problem if they weren't constructed to code.
That is another can of worms . . .

 

[BOOTY MONSTER]

"AS for home water pipes and electrical systems; they can be a problem if they weren't constructed to code."

up to code or not don't use them .


Special Publications | Technical Publication #32

Using Water Pipe & Service Joints For RF Grounding - Please Don't
It's probably done most often for the simple convenience of time and effort, but there's little to be gained and frequently a lot to lose by using cold water pipes, gas pipes, and electrical outlet box connections as RF or lightning protection grounds.

Good grounding is a critical and integral part of good telecommunication station design. Whether the application is receive only, transceiving, data delivery, or otherwise modern solid state equipment is internally delicate, and good grounding is a key factor in maintaining clean spectrum operating and overvoltage protection. Unfortunately, it is seen as a quick ten minute afterthought to many installations.

In their haste to finish ground connections are commonly made with a piece of "off the shelf" wire connecting radio equipment chassis to whatever is nearby that may eventually reach ground. But the most important factor in good neutral connections is length of lead from chassis to earth entry point -not the specific materials of wire sizes used. Here are a few guidelines to follow when installing ground connection systems:

Cold water pipes make poor grounds in most cases because the length of copper pipe to earth is often very long. Any lead over ten feet probably should be avoided for most applications. Additionally, pipes of this type connect through numerous solder-sweated joints, bends, and possibly even conversion to plastic pipe (a good insulator) before reaching ground. The fact that the pipe may have water inside is irrelevant. When such systems are used in transmitting service the piping becomes part of the radiating structure and ground level radiation will often be severe, causing interference to other services or neighbors.
Never, ever, ever use natural gas pipes for ground connections. In a lightning event a seem crack or rupture of a gas line can be explosive. Hot water lines used in conjunction with gas water heaters should be avoided for the same reason. Be sensible-stay well away from dangerous ignition sources!
When designing a telecommunication installation keep equipment at or below ground level if at all possible. Locate the equipment close to an outside wall where short grounding connections can be made. Or drive a ground rod through the floor downward into a crawl space if present where short distance ground can be found. Borrow or rent a hammer drill to drill a hole through concrete slabs or floors where a ground rod may be inserted. Ground underneath such places is nearly always moist and very conductive. If drilling through a slab be sure to avoid pipes that may be in the concrete! Consult the builder or house plans.
If the facility must be elevated off the ground run ground wire straight down to keep the distance as short as possible, and be sure to route all antenna leads, rotator wires, etc. to ground first (where lightning protection devices are installed), and then up to the equipment.
Electrical service box connections generally make poor grounds for the same reason as cold water pipes. The leads are lengthy, the wire size small, and the integrity of the earth connection is often compromised by age, poor initial installation, corrosion, dissimilar metal conversion, loose screws, etc.
The moral is simple - put some effort in good grounding. Keep leads short, wire size large, connections tight and weatherproof, and grounding electrodes wet. It will probably save you from more headaches than aspirin!

 

[Robb]

Yup.
The thing about plumbing and electrical as a 'can of worms'; is that if you use the sink to wash dishes, taking a bath, or taking a leak - can all be considered part of the ground path. People have been killed in the bath tub, or even talking on a land-line telephone. Or touching anything electrical at the moment lighting strikes. Happened before, and will doubtless happen again.

 

[Captain Kilowatt]

The most effective way to prevent damage from a direct strike is to disconnect your transmission lines. No connection = no current.

As for grounding,everything should be grounded at one common point. That is all grounds, lightning, RF, electrical safety, etc. should all be joined together at only one point and that is usually at the electrical entrance panel but not necessarily so. When disconnecting your transmission line you do not and should not disconnect any ground cables. if your ground is installed properly then nothing will happen to the gear connected to the ground. It is a good idea to unplug the gear from the AC outlet.

When grounding a tower it is good engineering practice to use at least three ground rods,each connected to a separate tower leg using wide solid flat copper strap. Heavy wire is acceptable as long as it is a bare minimum of 6 gauge and something like 1 gauge is even better. Braided flexible copper strap is only to be used as a last resort as it has a much higher inductance than wire or flat strap due to the weave. Properly done ($$$) a radio station can remain undamaged even if it takes a direct strike while nothing is disconnected but unless you have deep pockets you will have to decide how much inconvenience you are willing to put up with versus how much damage you are willing to accept.

A couple years ago I had the power line in front of the house take a direct hit. My coax cables were disconnected but not my rotator cables or the AC service. All my gear was fine but I lost a DVD player, a network card in my computer and a deep freeze compressor motor. I am sure that if the coax was connected the induced currents would have taken something out.

Many years ago I had a direct strike on my tower.All cables were disconnected but the grounds were still connected as was the AC power. The antenna at the time was a Wilson Shooting Star. I had no damage other than an overheated ground connection on one of the rods.

This year I plan to completely replace my entire entire antenna system from the ground up (no pun intended) and will pay special attention to my grounding techniques.

 

[Captain Kilowatt]

Forgot to add that some people think that adding a ground to your antenna or tower will make it attract lightning. That is 100% FALSE. The electrical charge that builds up on an object just before it gets hit is high voltage/very low current, essentially a static charge, and will happen even if that object is made of wood. Ever hear of a tree being hit by lightning? The idea of installing a good ground or lightning rod is that IF and WHEN that object gets hit there is a good low impedance path to ground to safely shunt the energy. Again, a ground and/or lightning rod DOES NOT ATTRACT LIGHTNING. It provides a safe path to ground IF lightning should hit.

I had an FM transmitter get hit four times one night while I watched it from a few miles away and God knows how many times before/after I left as it was not safe to enter the site. After the storm passed I went to the site expecting untold damage. All I had was a blown high voltage rectifier stack in the plate supply. All the associated VHF/UHF gear as well as all the audio gear was working 100%. We used four inch wide copper flat copper strap for grounding EVERYTHING. I had the local sheet metal shop cut up a sheet of copper into four inch wide by eight foot long strips. Back then in 2003 it cost less than $200 but today......$$$

 

[RatsoW8]

Forgot to add that some people think that adding a ground to your antenna or tower will make it attract lightning. That is 100% FALSE. The electrical charge that builds up on an object just before it gets hit is high voltage/very low current, essentially a static charge, and will happen even if that object is made of wood. Ever hear of a tree being hit by lightning? The idea of installing a good ground or lightning rod is that IF and WHEN that object gets hit there is a good low impedance path to ground to safely shunt the energy. Again, a ground and/or lightning rod DOES NOT ATTRACT LIGHTNING. It provides a safe path to ground IF lightning should hit.

I had an FM transmitter get hit four times one night while I watched it from a few miles away and God knows how many times before/after I left as it was not safe to enter the site. After the storm passed I went to the site expecting untold damage. All I had was a blown high voltage rectifier stack in the plate supply. All the associated VHF/UHF gear as well as all the audio gear was working 100%. We used four inch wide copper flat copper strap for grounding EVERYTHING. I had the local sheet metal shop cut up a sheet of copper into four inch wide by eight foot long strips. Back then in 2003 it cost less than $200 but today......$$$

Capt. K,

This is what I'm saying. That commercial radio tower might as well have had a sign on top saying "Truckers and Lightning Welcome"...it was a prime target for s strike. High profile and low resistance path to earth, which is really what lightning is looking for right? And it was professionally grounded, bonded, etc. to provide a path to earth while doing minimal damage to station equipment. But heck, I wouldn't have wanted to be within 100 yards of that installation when it was taking lightning hits.

I don't want my antennas at home being struck multiple times either so I believe I have a very low profile and low potential for a strike. Well..I know I do now because I use dipoles but, I did when I had a tower and yagi up in the air.

So, since I'm not putting up a 1000 foot lightning rod that is bound to get hit and require elaborate expensive grounding systems to dissapate said hits...I choose to make my antennas as uninviting to lightning as possible.

I do however, ground (RF) my station equipment seperatly.

No one even brought up he most likely way your going to lose equipment to lightning. I've lost electronics to indirect strikes and power line hits but never radio gear. So, before you toss your coax out the window unplug all your equipment from the walls too. I also disconnect my cable modem and tv's. Lickily we have underground utilities so my only worry is a nearby strike.

 

[trailboss]

The only time my coax is connected is when I am using that antenna, if not it is disconnected at the feed through to the shack.

Towers grounded, fed through grounded.

Lightning strikes are catastrophic, knock on wood I have not lost any gear due to lightning, antennas is a different story, Lightning capitol of the world here in Florida.

If you are not using the rig, unplug it and disconnect the coax and get the coax out of the building. Lightning will jump from the coax to the nearest ground inside the building (radio chassis) so just disconnecting the coax is not enough.

Probably not a bad practice, you never know when you might be called away on a moments notice, or not be able to get to the house ahead of the storm.

I would hate to be this guy...who says lightning doesn't strike twice?

http://www.youtube.com/watch?v=53uSiTbVDVc&feature=player_embedded

It looks like he had the piss zapped out of him!