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#41
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On Sun, 15 Feb 2004 15:58:03 -0500, w_tom wrote:
A person who so poorly protected his own home as to suffer completely unnecessary computer and TV damage will now teach me? One who even posted the classic urban myth about concrete damage to prove Ufer grounding does not work? You just realized something: someone on the other side does have a few decades of experience and engineering degrees. If you had one, then the concept of resistance and impedance would have been correctly posted. However someone even did read 'tower talk' - and posted citations from 'tower talk' in direct contradiction to your posted myths. Well at least you are not posting personal attacks this time. The world can get better. In the meantime this is a discussion about the OPs antenna mast; not a forum for personal attacks. The OP must earth his antenna mast both for lightning protection AND as required by the National Electrical Code. That answers his question. Please feel free to address the purpose of this thread - the Original Poster's original request for information - Zeeeeeeee3 originally posted: It has several times, which you have chosen to ignore. Use proper grounds and disconnect his equipment from the antenna and mains. Your answer is use proper grounds, but don't disconnect any equipment. Now which one makes more sense? Which one would better protect his equipment? Which one offers more protection? |
#42
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In , Lancer
wrote: On Sun, 15 Feb 2004 15:58:03 -0500, w_tom wrote: A person who so poorly protected his own home as to suffer completely unnecessary computer and TV damage will now teach me? One who even posted the classic urban myth about concrete damage to prove Ufer grounding does not work? You just realized something: someone on the other side does have a few decades of experience and engineering degrees. If you had one, then the concept of resistance and impedance would have been correctly posted. However someone even did read 'tower talk' - and posted citations from 'tower talk' in direct contradiction to your posted myths. Well at least you are not posting personal attacks this time. The world can get better. In the meantime this is a discussion about the OPs antenna mast; not a forum for personal attacks. The OP must earth his antenna mast both for lightning protection AND as required by the National Electrical Code. That answers his question. Please feel free to address the purpose of this thread - the Original Poster's original request for information - Zeeeeeeee3 originally posted: It has several times, which you have chosen to ignore. Use proper grounds and disconnect his equipment from the antenna and mains. Your answer is use proper grounds, but don't disconnect any equipment. Now which one makes more sense? Which one would better protect his equipment? Which one offers more protection? Hey Lancer, don't make it too simple. It's all about "impedance", don'cha know? -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
#43
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On Sun, 15 Feb 2004 15:04:05 -0800, Frank Gilliland
wrote: In , Lancer wrote: On Sun, 15 Feb 2004 15:58:03 -0500, w_tom wrote: A person who so poorly protected his own home as to suffer completely unnecessary computer and TV damage will now teach me? One who even posted the classic urban myth about concrete damage to prove Ufer grounding does not work? You just realized something: someone on the other side does have a few decades of experience and engineering degrees. If you had one, then the concept of resistance and impedance would have been correctly posted. However someone even did read 'tower talk' - and posted citations from 'tower talk' in direct contradiction to your posted myths. Well at least you are not posting personal attacks this time. The world can get better. In the meantime this is a discussion about the OPs antenna mast; not a forum for personal attacks. The OP must earth his antenna mast both for lightning protection AND as required by the National Electrical Code. That answers his question. Please feel free to address the purpose of this thread - the Original Poster's original request for information - Zeeeeeeee3 originally posted: It has several times, which you have chosen to ignore. Use proper grounds and disconnect his equipment from the antenna and mains. Your answer is use proper grounds, but don't disconnect any equipment. Now which one makes more sense? Which one would better protect his equipment? Which one offers more protection? Hey Lancer, don't make it too simple. It's all about "impedance", don'cha know? Couldn't I get a correct impedance match with a 1/4 wave of bus bar? Now what did he say the frequency of lightning was? |
#44
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In , Lancer
wrote: On Sun, 15 Feb 2004 15:04:05 -0800, Frank Gilliland wrote: In , Lancer wrote: On Sun, 15 Feb 2004 15:58:03 -0500, w_tom wrote: A person who so poorly protected his own home as to suffer completely unnecessary computer and TV damage will now teach me? One who even posted the classic urban myth about concrete damage to prove Ufer grounding does not work? You just realized something: someone on the other side does have a few decades of experience and engineering degrees. If you had one, then the concept of resistance and impedance would have been correctly posted. However someone even did read 'tower talk' - and posted citations from 'tower talk' in direct contradiction to your posted myths. Well at least you are not posting personal attacks this time. The world can get better. In the meantime this is a discussion about the OPs antenna mast; not a forum for personal attacks. The OP must earth his antenna mast both for lightning protection AND as required by the National Electrical Code. That answers his question. Please feel free to address the purpose of this thread - the Original Poster's original request for information - Zeeeeeeee3 originally posted: It has several times, which you have chosen to ignore. Use proper grounds and disconnect his equipment from the antenna and mains. Your answer is use proper grounds, but don't disconnect any equipment. Now which one makes more sense? Which one would better protect his equipment? Which one offers more protection? Hey Lancer, don't make it too simple. It's all about "impedance", don'cha know? Couldn't I get a correct impedance match with a 1/4 wave of bus bar? Now what did he say the frequency of lightning was? I don't think he did, but if you post an arbitrary value I'm sure he will provide you with the correct information. I -do- know that lightning is monitored by listening to the Schumann (sp?) resonance, which is a constantly changing frequency down around 8 Hz. So let's see, we would need a ground strap that is resonant over a frequency range of, say, around 1 to 20 Hz..... so how much money are you willing to spend on this little project? Because the only way I see of doing this is with a megawatt negative impedance converter! -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
#45
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Frank Gilliland wrote:
In , Lancer wrote: On Sun, 15 Feb 2004 15:04:05 -0800, Frank Gilliland wrote: In , Lancer wrote: On Sun, 15 Feb 2004 15:58:03 -0500, w_tom wrote: A person who so poorly protected his own home as to suffer completely unnecessary computer and TV damage will now teach me? One who even posted the classic urban myth about concrete damage to prove Ufer grounding does not work? You just realized something: someone on the other side does have a few decades of experience and engineering degrees. If you had one, then the concept of resistance and impedance would have been correctly posted. However someone even did read 'tower talk' - and posted citations from 'tower talk' in direct contradiction to your posted myths. Well at least you are not posting personal attacks this time. The world can get better. In the meantime this is a discussion about the OPs antenna mast; not a forum for personal attacks. The OP must earth his antenna mast both for lightning protection AND as required by the National Electrical Code. That answers his question. Please feel free to address the purpose of this thread - the Original Poster's original request for information - Zeeeeeeee3 originally posted: It has several times, which you have chosen to ignore. Use proper grounds and disconnect his equipment from the antenna and mains. Your answer is use proper grounds, but don't disconnect any equipment. Now which one makes more sense? Which one would better protect his equipment? Which one offers more protection? Hey Lancer, don't make it too simple. It's all about "impedance", don'cha know? Couldn't I get a correct impedance match with a 1/4 wave of bus bar? Now what did he say the frequency of lightning was? I don't think he did, but if you post an arbitrary value I'm sure he will provide you with the correct information. I -do- know that lightning is monitored by listening to the Schumann (sp?) resonance, which is a constantly changing frequency down around 8 Hz. So let's see, we would need a ground strap that is resonant over a frequency range of, say, around 1 to 20 Hz..... so how much money are you willing to spend on this little project? Because the only way I see of doing this is with a megawatt negative impedance converter! You guys are all over this topic and it's really blowing my hair back. Can you guy's condense it to your opinion of the best/cheapest way to ground lets say..an omni on a roof-top or tower? Best being a relative term. I'm sure the advice will save at least one person from getting blasted, and make people aware that you can't just put a hunk of metal in the air without considering lightning. Thx. -- Go 40 42 12 |
#47
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Frank Gilliland wrote:
First, sink a ground rod at the point where the coax will enter the house. If you have a basement next to the ground rod, sink a couple more rods so they are separated by ten feet or more and in the path of the coax. Some people like to prep the ground by soaking with sal****er, but in my experience that makes the rod corrode before its time, then the salt leeches away into the ground water, leaving a very poor ground in a very short time. I use galvanized pipe as opposed to copper rods because they have a larger diameter (more rod-to-ground contact = lower resistance), and they last longer. You can also thread the pipe for a super-neat installation of a waterproof box...... Next is the coax installation. Run the coax down the mast or side of the house to the ground rod. Don't run the coax near any wiring inside the house. You can detect house wiring with a cheap metal detector. Avoid sharp turns as much as possible. At the ground rod it helps to have a waterproof box because you need to cut the coax, ground the shield, and shunt the center conductor to ground with a choke (as per the diagram I made yesterday). About the choke: This serves two purposes. First, it shunts static electricity from the antenna to ground. Second, it provides a path for lightning if it should strike. Since the lightning will arc across every loop in the choke, the inductance value isn't critical just as long as it is high enough to block your RF (about 1 mH or larger for HF and above), and the wire size is large enough to handle some current (#14 or larger should be fine). One of those heavy-duty hash chokes for ignition noise is ok, or you can wind your own -- use a large iron bolt for a core and wind about 50 turns of #10 or #12 house wire. If you aren't running much power, you can slit the insulation along the length of the coil so it will arc at a lower voltage. Then run the coax up into the house along side the grounding strap. Tie them together with cable-ties if you want. Again, it's important that you run these so they don't come close to any house wiring, and they should enter at a location that is clear of easily combustible stuff. Terminate the ground strap with a really big alligator clip, jumper cable clamp, or whatever you have that makes a really good connection and can be easily disconnected. The ground clamp from an arc welder is almost ideal. Above the point where the coax and grounding strap enter the house, make a hook or post where you can hang both when not being used. Remember that if lightning hits, it's very possible that these will jump straight out from the wall and dance around like a water hose, so make sure they are held securely in place. Inside the house, make yourself a grounding bus bar of copper or aluminum. Put this on the back of your bench and use it to ground all your equipment. To this you clamp on your grounding strap. When not using your bench, unhook the grounding strap along with the coax and stow it away. Also, to protect the coax, use an appropriate socket and short it out before you stow it. When should you unhook your antenna? There is a thing called the 30-30 rule: If you hear thunder less than 30 seconds after you see the lightning, unplug. Don't plug in again until 30 minutes after the last thunder. That's pretty safe. You can even improve on that by building a lightning detector, many of which will indicate lightning even before you can hear the thunder. How's that? Oh, I almost forgot..... coax length!!!!! The low impedance of the ground will be reflected at the radio when the length of the coax & ground strap, from the ground rod to the radio, are 1/2 wavelength. This means 1/2 wavelength -without- consideration of velocity factor because we want a low impedance -ground-. And this means -- you guessed it -- 18 feet of coax! Very informative Frank, make sure we can reference that. Dunno if average joe will completely comply, but he can't say you didn't worn him! We pushed poles in the ground with the bobcat and post hole digger, mostly for lightning. Out here where I live, by the time the fire dept gets here with the tanker (no hydrants)you're toast. Ground is good. (like you said) -- Go 40 42 12 |
#48
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"w_tom" wrote in message ... Cited was an industry professional who demonstrate simple protection even for amateur radio installations. He discussed protection without damage for *all* radios, including repeaters. You think effective earthing requires what commercial broadcasters install? Yes, some so deny the power of earthing. Very little protects radios from most direct lightning strikes. However some will cry that such earthing cannot protect from the rare 1%. If earthing is only 99% effective, then no money should be spent - all earthing is useless? Reality, effective protection from direct lightning strikes is about simple and inexpensive earthing. Frank Gilliland has even posted unrealistic and fictional numbers, and then denies the power of earthing - a concept well proven in virtually every town throughout the world. BTW Frank, to correct your post: low *resistance* (not impedance) ground is fine for AC line protection. A low *impedance* ground is necessary for lightning protection. One must know the difference to understand simple earthing concepts - and why earthing is so effective. How can you be so critical of earthing and not even know the most basic of basics - impedance verse resistance? Even basic numbers such as the typical pulse width are silly speculation. Typical lightning strike is a classic 8/20 usec. That is microseconds - not 0.1 seconds - which is why lightning does not have the energy content of myth. Furthermore, 1,000,000 volts does not appear at that lightning strike. In fact a major destructive direct strike to the building is well defined in research papers - as to not exceed 6,000 volts. One should first learn the science. Basic electrical circuit theory makes it obvious why the millions of volts up there don't appear down here. Either those millions of volts must be up there or down here - cannot exist in both locations. Again, first semester circuit theory that every graduate of West Point and Annapolis has learned. Please first learn that basic circuit theory before disputing IEEE papers, other well proven research, and NEC requirements. Correctly noted is that most people don't climb trees to search for lightning damage to trees. But then researchers such as Alan Taylor of the US Forestry Service are not just most people. Lightning has such low energy that most every tree directly struck has no appreciative damage. Speculate all you want. He did the work and wrote the paper. Using your reasoning for why earth cannot conduct the electricity even in a badly polluted salt marsh: then obviously lightning could never conduct miles across the sky and obviously lightning does not strike a non conductive earth. Why does air conduct miles of lightning that only contains millions of volts? First learn the many stages of how air and earth become such excellent conductors. Does a cloud strike 5 miles diagonal to connect cloud to charges on earth? Of course not. Lightning travels 3 miles straight down and then 4 miles through earth to complete a circuit. Lightning takes a more conductive path via air and earth rather than an electrically longer 5 mile path only through air. Conductive earth is also why earthing a direct strike (the single point earth ground) is such effective protection from a direct strike. Because even simple concepts of impedance verses resistance are not understood, then even safety grounds (third prong in wall receptacle) are confused with earth ground. Safety ground is different from motherboard ground is different from chassis ground is different from automobile ground is different from breaker box ground is different from power plant ground is different from earth ground. Most all are interconnected, but are still electrically different. Learn about impedance. No earth ground is found in wall receptacles because the wire length - and therefore impedance - of that third prong wire is just too far from earth ground. Again, one must first understand impedance to appreciate what world renown experts (some quoted here) have said about earthing. It takes but a few milliamps to kill a human. Does that prove lightning must be a high energy event - because it too kills? Learn how easy a human can be killed before posting such assumptions. Even posted is that a buried coax is protected from lightning transients. That is ridiculous as even made bluntly obvious in a Polyphaser application note about damage to an improperly earthed telephone exchange; transient damage via buried wires. Obvious in that long reply - even basic electrical concepts are not understood. Real world professionals and generations of scientific experience prove basic earthing is effective protection. Even the NEC requires OP to earth ground his antenna also for human safety. Basic electrical knowledge - impedance verses resistance - was not even understood and still Frank said everyone is wrong about earthing. Frank Gilliland wrote: CB radio antennas are not commercial station towers. The latter are verticals that have a direct connection to ground and the ground radials. Actually, an AM broadcast tower is almost a perfect lightning rod by design because it not only shunts the lightning directly to ground, but also distributes the power from the strike over the whole counterpoise field. So the tower stays at a relatively low potential even during a direct strike. And what -does- manage to sneak onto the line has to deal with some rather expensive protection devices. Antennas mounted seperately on towers (FM/TV BC, cell, commercial, etc) have the same problems as any other antenna, but those problems are usually minimized by the use of coax. More below. Let's start with his numbers. Millions of volts? Yes. But same voltage does not appear everywhere in a circuit - basic circuit theory. Those millions of voltage are in the sky. Surge protection is about making those millions of voltage appear elsewhere which is why industry professionals discuss impedance. A low impedance connection to earth means no millions of volts. A low impedance ground is fine for AC line protection, but it doesn't guarantee lightning protection. We have all heard that lightning takes the shortest path to ground, but that's not really true since electricity will take EVERY path to ground available. Lightning creates it's own conduit from the clouds, but once it hits a conductor on the ground it behaves just like any other form of electricity -- almost. The fact is that wire has resistance, and the resistance of copper increases with temperature, which is what happens when it passes the current from a lightning strike. When that happens it will continue it's path to ground (assuming the wire doesn't fuse), but other paths will share more of the load. And because there is a resistance, there will also be a voltage potential across that resistance. If that voltage potential is high enough it will happily arc over to another ground path, and frequently does. More below. Millions of amps? Only in dreams. Most lightning is below 20,000 amps and of such short duration as to not be high energy. Lightning typically so low energy at the strike location (not to be confused with what is miles above) that well over 90% of all trees struck leave no indication of that strike. Let's take your figure of 20,000.... no, let's go even lower. Let's say only 1000 amps @ 1,000,000 volts. And let's say this is an unusual strike in that it only hits once, not multiple times like a normal strike. And let's say the duration of the hit is 1/10 of a second. This will be a pathetic bolt of lightning to be sure! Ok, so let's do some numbers: 1,000,000 Volts x 1000 Amps = 1,000,000,000 Watts 1,000,000,000 Watts x 0.1 sec = 1,000,000 Watt/sec One million joules is "low energy"? Get a grip. Trees struck by lightning usually -do- leave an indication of being struck, but most people don't climb them to search for the point of contact, which is typically nothing more than a spot about one or two cm in diameter that has been charred. And while the reason trees are able to survive direct lightning strikes is still the subject of debate, the reason they make good lightning rods (efficiently conducting the strike to ground) shouldn't be so suprising when you take a look at a cross-section of the root structure -- interesting how it resembles an electrical discharge, isn't it? Ok, back to your low impedance ground. A ground rod is used to make an electrical connection to the earth. But the impedance of that connection can be anywhere from a few ohms to a few hundred ohms, depending on the type of rod and the conditions of the soil. Let's just say we have a ground with an unbelievable impedance of 1 ohm (a solid-silver rod in a heavily mineralized salt-water marsh that was recently used for dumping copper turnings from a very poorly run machine shop)..... 1000 amps x 1 ohm = 1000 volts So with an almost impossibly good ground and a puny bolt of lightning you -still- have 1000 volts at the top of your ground rod. So a more typical ground impedance of 50 ohms (not coincidence) and a more typical lightning strike of 10,000 amps will put 500,000 volts on your grounding strap.....YIKES!!!!! This is a fact, and it certainly doesn't seem to jibe with your statement that the voltage at the bottom is insignificant! How big need a wire be to shunt (earth) lightning? Even the US Army training manual TM5-690 requires 10 AWG wire to conduct the direct lightning strike without damage. Ever hear the term "military intelligence"? Same wire found in 20 or 30 amp AC electric boxes because lightning is not the millions of amps so often claimed in urban myths. Unlike Frank, numbers are provided by multiple, reliable sources. The ground wire in house wiring is intended for fault protection, not lightning strikes. For example, if the hot wire in your vintage all-metal Craftsman drill suddenly comes loose and shorts to the case, since the case is grounded it will shunt the majority of the current to ground through the ground wire, not through the person using the drill. And if your breakers and wiring are up to code (neutral grounded at the box), that current lasts only for a very short time, limiting any damage to the person and the drill. Therefore, the ground wire in your house doesn't need to be as thick as the main wires, and it isn't. Next time you visit your local hardware store, look at the specs on a spool of house wire -- hot and neutral may be #10 while ground will be #12. Another spool may have a pair of #12 wires and #14 for ground. If this ground wire was intended for lightning protection, wouldn't it all be the same size? Fact: the NEC doesn't define ground wire size based on it's ability (or inability) to protect against lightning. Another who does this for a living: From Colin Baliss "Transmission & Distribution Electrical Engineering": Although lightning strikes have impressive voltage and current values (typically hundreds to thousands of kV and 10-100 kA) the energy content of the discharge is relatively low ... Relative to what? or Martin A Uman in All About Lightning Most of the energy available to the lightning is converted along the lightning channel to thunder, heat, light, and radio waves, leaving only a fraction available at the channel base for immediate use or storage. Then I guess all the people that have been killed by lightning didn't die from the power in the lightning, did they? And all the damage to electrical equipment caused by lightning wasn't from the lightning at all, was it? And that pro golfer that was knocked flat on the links by a nearby strike must have been hit in the head with a ball at the exact same time, huh? No, no and no..... .... It's obvious that you have no experience in the real world with lightning damage. Get some. While this pains me, Frank's right. You can go on with your babble, but there's no reasonably priced grounding system that will protect you as good as unplugging everything from the wall and antenna. Landshark -- Hard things are put in our way, not to stop us, but to call out our courage and strength. |
#49
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In ,
wrote: ..... We pushed poles in the ground with the bobcat and post hole digger, mostly for lightning. Out here where I live, by the time the fire dept gets here with the tanker (no hydrants)you're toast. Here's a little trick if you use a pipe for a ground rod: Thread both ends of the pipe. On the top put a fitting that will accept a garden hose. On the bottom put a reduction fitting (to be used as a nozzle). Hold the pipe vertical, turn on the water full blast, then let the water drill the hole. When you are done just unscrew the top fitting, and PRESTO!!! A great ground rod without a lot of fuss. BTW, this doesn't work very well in areas where there are a lot of large rocks in the ground..... -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
#50
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Frank Gilliland wrote:
In , wrote: ..... We pushed poles in the ground with the bobcat and post hole digger, mostly for lightning. Out here where I live, by the time the fire dept gets here with the tanker (no hydrants)you're toast. Here's a little trick if you use a pipe for a ground rod: Thread both ends of the pipe. On the top put a fitting that will accept a garden hose. On the bottom put a reduction fitting (to be used as a nozzle). Hold the pipe vertical, turn on the water full blast, then let the water drill the hole. When you are done just unscrew the top fitting, and PRESTO!!! A great ground rod without a lot of fuss. BTW, this doesn't work very well in areas where there are a lot of large rocks in the ground..... That's a slick idea, we're sandy loam and clay around here. Next time I sink a ground rod I'll remember the water. -- Go 40 42 12 |
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