Worse Case Scenario - Lightning Strike?

[Captain Kilowatt]

IMO that 10 ga wire will act like a fuse in the event of a strike. I am surprised the NEC allows such a small wire. Up here EVERYTHING requires a minimum of 6 ga wire for grounding. Even your satellite dish has to be grounded with 6 ga.

 

[BOOTY MONSTER]

this is just my opinion ...... and i have no problem being corrected if im wrong since im here to learn ...


it seems to me ........ that since metal is a excellent conductor that if the ground is charged to attract lightning that having a metal pole sticking high up out of it and having the antenna sticking up even higher (and grounded to earth) carries that charge up even higher and then concentrates it to a small point at the tip of the antenna making it essentially a lightning rod . my thinking is that insulating/isolating the mast from ground contact and the antenna from mast and ground contact reduces the likely hood of them attracting lightning . and as i said i disconnect the coax in the house if im away long or notice bad weather coming in .

 

[Robb]

this is just my opinion ...... and i have no problem being corrected if im wrong since im here to learn ...


it seems to me ........ that since metal is a excellent conductor that if the ground is charged to attract lightning that having a metal pole sticking high up out of it and having the antenna sticking up even higher (and grounded to earth) carries that charge up even higher and then concentrates it to a small point at the tip of the antenna making it essentially a lightning rod . my thinking is that insulating/isolating the mast from ground contact and the antenna from mast and ground contact reduces the likely hood of them attracting lightning . and as i said i disconnect the coax in the house if im away long or notice bad weather coming in .

Mostly right...Except for allowing the lightning from making a direct path - this would just allow it to pass thru too many other paths/things (like your house - perhaps) instead of going straight to ground. If it is going to come down near you - because the Earth potential charge is great enough - you can't stop it. Which would you rather have? Better grounded antennas have a better chance of survival if they pass the current - rather than resisting it. I don't think any of us can afford to do it the way broadcast stations do it. I could b wrong about the method/cost .

 

[The Jerk]

The whole idea behind the 10ga wire isn't to discharge energy from a strike, but to dissipate and prevent the STATIC CHARGE (caused by wind friction) from building up on the antenna...that is what caused the lightning to be attracted to a particular thing. Being "insulated" from the ground makes that charge stay on the antenna, and not dissipate to somewhere else.

As previously noted, 6ga wire will not handle the current from a lightning strike. I believe the reason 6ga wire is specified for electric panels and such is the fact your *could* have as much current as you have service electric passing though it in a direct short...in other words 200A in most cases. Its not really there to protect from lightning strikes. There's no high amperage "electrical" connection to your antenna, therefore; you don't need the heavier wire to carry a lot of amperage away in the case of a direct short.

Ground the antenna isn't to survive a direct strike, but merely dissipate energy build up to HELP prevent the strike from occurring. As we all know, lightning is unpredictable.

And don't get me wrong, this is just what I have read on the net over the last day or so...and this is how I understand things.

 

[The Jerk]

And although out-of-date slightly...my father is bringing down his copy of the 2008 National Electric Code (NEC) tomorrow...so I should be able to read through that and at least be "up to code".

 

[bamacj]

I deal with the "nec " at work and it can mis-lead you. The nec recomendations are the very least required to do the job, not the max.

Forget about a direct hit, thats usually a total loss. As stated by "the jerk" grounding and bonding is to disipate the static charge from your tower and to try and direct a hit to ground without going through your equipment.

 

[ROADTRAIN]

I a little late to this tread..... lightening arrestor AR-10 from claysradioshop.com it can be used for both Mobil and base, however the base application is allot like ppl are describing here. Go to the site and check it out in accessories section. For $ 5.95 it may be some really cheap insurance.....

ROADTRAIN

 

[Captain Kilowatt]

this is just my opinion ...... and i have no problem being corrected if im wrong since im here to learn ...


it seems to me ........ that since metal is a excellent conductor that if the ground is charged to attract lightning that having a metal pole sticking high up out of it and having the antenna sticking up even higher (and grounded to earth) carries that charge up even higher and then concentrates it to a small point at the tip of the antenna making it essentially a lightning rod . my thinking is that insulating/isolating the mast from ground contact and the antenna from mast and ground contact reduces the likely hood of them attracting lightning . and as i said i disconnect the coax in the house if im away long or notice bad weather coming in .

Since that static charge can span thousands of feet in the air do you really think you can effectively isolate the antenna from ground a few inches away? WHEN lightning hits the antenna you WILL want a ground path other than the feedline that comes into the house. I know a fellow that had an A99 mounted on the peak of his house without any grounding at all other than the coax shield. His radio was in the kitchen. He took a hit and the lightning burned the coax cable all along the cable run, actually blew the cabinets off the kitchen wall as the cable was run behind them, totally destroyed his radio and set fire to the house all because lightning was looking for a path to ground and couldn't find one. As for the A99, well we never did find anything other than a couple fiberglass splinters.

The whole idea behind the 10ga wire isn't to discharge energy from a strike, but to dissipate and prevent the STATIC CHARGE (caused by wind friction) from building up on the antenna...that is what caused the lightning to be attracted to a particular thing. Being "insulated" from the ground makes that charge stay on the antenna, and not dissipate to somewhere else.

As previously noted, 6ga wire will not handle the current from a lightning strike. I believe the reason 6ga wire is specified for electric panels and such is the fact your *could* have as much current as you have service electric passing though it in a direct short...in other words 200A in most cases. Its not really there to protect from lightning strikes. There's no high amperage "electrical" connection to your antenna, therefore; you don't need the heavier wire to carry a lot of amperage away in the case of a direct short.

Ground the antenna isn't to survive a direct strike, but merely dissipate energy build up to HELP prevent the strike from occurring. As we all know, lightning is unpredictable.

And don't get me wrong, this is just what I have read on the net over the last day or so...and this is how I understand things.

Trust me,I spent 22 years in the broadcast business and had FM and VHF/UHF antennas on 300 foot towers atop very high hills as well as many AM broadcast towers to protect. You DO use a heavy ground connection to protect the antennas and connected equipment in the event of a lightning strike. We used copper strap two or three inches wide and sometimes four inches wide for the main ground buss connecting to the TX chassis and main feedline coming into the building.In the case of tall AM towers you also use static drain chokes and spark gaps in addition to heavy ground connections. Properly grounded the lightning should follow a path around the equipment and safely be dissapated to ground. In most cases lightning can strike a commercial installation amnd the most that happens is the TX pops off the air for a few seconds due to detecting a high SWR and then resets itself. The TX'ers see the voltage from a strike as a high SWR situation. The VHF/UHF stuff just keeps on working through a strike.

I a little late to this tread..... lightening arrestor AR-10 from claysradioshop.com it can be used for both Mobil and base, however the base application is allot like ppl are describing here. Go to the site and check it out in accessories section. For $ 5.95 it may be some really cheap insurance.....

ROADTRAIN

I wouldn't put a lot of faith in those AR-10 arrestors. The breakdown voltage is too high and will allow the static to build up to a damaging level before they fire. In the event of a direct strike they offer very little protection. Often the weak link is the small attachment screw meant to connect it to ground.

 

[TonyV225]

CK Im with ya here I am a true believer that if its your day to take that one in a millon chances of a hit then its your day and theres nothing a person can do because its gonna happen your taking the hit reguardless what you do and unless you spend what broadcast stations do with the same effectivness then all a person can do is what I do disconnect and get the coax the hell out of the house.

Lightning is so unpredictable on what its actually going to do or destroy on its hit that we just cant map out exactly what do do. All we can do is take the precautions and hope hope hope for the best out of what we do to protect. There are hundreds of bits and pieces of advice one can get but how it all works in the end is the truth in the matter because we can do all we can but there is no testing it we have to see how effective everything was or is in that very strike we hoped wouldnt happen but we setup for.

I know people that setup with lightning protection that costed $1,000 and theres always something that still gets hammered being a TV or another device or several for that matter. You also have to take into consideration that for radio equipment it can really be a touchy subject because all it takes in most cases is a simple side flash from lightning to ruin the day hell static build up can do it alone if theres no bleed off. I went through that here with a tube amplifire lastyear when it was extremely windy but thats a whole nother conversation.

All in all you need to think about whats most important your house family equipment ETC and thats where you focus on thats why my Coax goes outside and tucked away in its dry box away fom the house.

 

[jazzsinger]

CK Im with ya here I am a true believer that if its your day to take that one in a millon chances of a hit then its your day and theres nothing a person can do because its gonna happen your taking the hit reguardless what you do and unless you spend what broadcast stations do with the same effectivness then all a person can do is what I do disconnect and get the coax the hell out of the house.

i think it might be safer getting your ass out the house more than your coax,lol.

just had a flashback to the movie scream when the reporter cried "White folks is dead, we getting the fuck outta here! "

got me thinking this guys philosophy could be equally applied to lightning.One smart cookie,i had tears streaming down my face at that one.

 

[Robb]

I deal with the "nec " at work and it can mis-lead you. The nec recomendations are the very least required to do the job, not the max.

Forget about a direct hit, thats usually a total loss. As stated by "the jerk" grounding and bonding is to disipate the static charge from your tower and to try and direct a hit to ground without going through your equipment.

Just a reminder here concerning lightning.
You only have one chance to get it right - should your station be struck.
Do what you can to make a direct path from the antenna to a well-established ground. Use braided wire - the largest gauge that you can use/get and at least three ground rods - especially if you have a tower and live in areas that are lightning prone (See ARRL recommendations 03 ). Remember to remove/unplug your gear from wall sockets and disconnect antennas when an electrical storm is approaching, as per ARRL recommendations.
Doing so can save your life, home, and property.

We are talking about hundreds of thousands of amps in a multi-discharge event. Never should lightning be treated lightly or an afterthought in your station layout.
:bdh:

 

[BOOTY MONSTER]

static charge/buildup on the antenna from being up in the air question ...


so will the ground through the coax then radio then house electrical system/ground allow that to dissipate ? if not would using one of these "Lightning Arrestors" at the radio or panel in the window with a meduim heavy gauge wire going to a ground rod be enough just for a static drain for the antenna ? i realy dont want to have the mast possibly radiating and bleeding into my or other folks electronics .

SkyThumper Lightning Arrestor

 

[Captain Kilowatt]

Booty, most of the time those lightning arrestors fail especially if they are the only path for lightning to take. They just cannot pass that 100,000 amps or so of discharge. The lightning will follow the cable into the house and you do not want that at all. The best step is the first step and that is to GROUND the antenna or tower base properly and that will shunt most of the energy to ground before it has a chance to follow the cable. Remember, lightning is lazy and looks for the easiest path to ground and if that happens to be your coax cable shield then that is tha path it will take.

Here is an interesting item that has been proven to drastically reduce the chances of a direct strike. We all know that a static charge must first build up on an object before lightning will strike it so the best thing to do is provide a means to safely bleed off that static quickly before it has a chance to build up. QWe also know that static will bleed off from a sharp point much easier than from a flat surface and the more sharp points tha better. Believe it or not but for a given height and location a multi-element beam is less likely to take a hit than an A-99 or similar antenna because the beam has more sharp points and element ends than the single element vertical. The devices shown below in the linl allow the static to bleed off quickly because of the number of steel spines. I have made a few using stainless steel aircraft cable and so far so good. Two year ago lightning struck the power line in front of the house but not the tower in the yard. May I was luck but maybe they helped. I do know I'll be making more of them for the next tower install.


http://www.lightningmaster.com/Adobe-Pdf/LM-PP-1.PDF

 

[BOOTY MONSTER]

CK i didnt mean to imply that i thought it would help with a actual lightning strike , im %100 it wouldnt i was wondering if it might help to reduce a static charge to reduce the likely hood of a lightning strike .

dont little pointy thinks on antennas attract and cause noise ?

 

[W5LZ]

And just for grins...
If you happen to know of any 'chimney sweeps' (chimney cleaners), or anyone connected with the oil field pipe cleaners, both use a 8 - 12" steel brush to clean chimneys and pipes. They usually have several old ones too worn to use. If you happen to catch them before they throw them away, they make fine static dissipaters. Had a neighbor for a while that did the oil field thingy, got several from him. I've seen several attached to towers and masts, doesn't have to be on the top, off to one side works fine.
I seriously doubt if I ever use them, come get'em or pay shipping and you can have them. I've even got boxes they'll fit into... Don't expect pretty! They ain't.
- 'Doc