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Ground antenna?
Was talking with someone the other day and mentioned that I had just
grounded the antenna (the mast, actually) to protect against lightning strikes, and they said that was not such a good idea because lightning is more likely to strike a path that goes straight to ground. Now I am not sure what to do. Anyone have any input on this topic? Ideas are gratefully received... Thanks, Dave |
Ground antenna?
On Thu, 15 Oct 2009 08:42:05 -0500, "Dave" wrote:
they said that was not such a good idea because lightning is more likely to strike a path that goes straight to ground. Hi Dave, Did they happen to mention what a great deal it was for that lightning to go directly to your radio instead? I suppose their next argument is that lightning won't strike an "insulated" antenna.... 73's Richard Clark, KB7QHC |
Ground antenna?
In message , Richard Clark
writes On Thu, 15 Oct 2009 08:42:05 -0500, "Dave" wrote: they said that was not such a good idea because lightning is more likely to strike a path that goes straight to ground. Hi Dave, Did they happen to mention what a great deal it was for that lightning to go directly to your radio instead? I suppose their next argument is that lightning won't strike an "insulated" antenna.... One reason for lightning conductors (and for grounding elevated conductors, like radio antennas) is that it helps to stop a high electrostatic charge from accumulating in the air immediately above them. The intention is to PREVENT a direct lightning strike, rather than conduct a strike to ground. Of course, if a direct strike DOES occur, an antenna (and even a stout lightning conductor) may be seriously damaged. -- Ian |
Ground antenna?
On Oct 15, 10:54*am, Ian Jackson
wrote: One reason for lightning conductors (and for grounding elevated conductors, like radio antennas) is that it helps to stop a high electrostatic charge from accumulating in the air immediately above them. The intention is to PREVENT a direct lightning strike, rather than conduct a strike to ground. Of course, if a direct strike DOES occur, an antenna (and even a stout lightning conductor) may be seriously damaged. -- Ian The only problem with that is that the charge is so quickly replenished that I think trying to bleed off the charge is a waste of time. Note the "brush" type conductors that supposedly dissipate the charge to avoid a strike. They don't really work too well, and when they do get struck, often you have blobs of molten metal flying about. The way I see it, the only way to really prevent a strike, and even then I think it's iffy, is to provide a shape that does not stream well. And then have a lightning rod which does stream well to take the strike vs the object that does not stream well. IE: a rounded ball on top of a mast does not stream as well as a sharp tip. This is why most flag poles have a ball on top. To reduce the likelihood of streaming. And even those can still be struck under some conditions. So I think trying to avoid a strike using such methods is more wishful thinking than anything. I look at it in a different way. I expect it to be struck, and it will if it's any decent amount of distance above the surrounding objects. It might take 6 months, or it might take 6 years, but it will be struck some day. Count on it. A strike does not know where it's going to hit until about the last 150 yards or so. Then the streamers from the ground are all pointing towards the down leader trying to entice it. Usually the strongest streamer in the area will attract the strike. And even that is never a sure thing. :/ So the best way to deal with lightning is to expect it to strike sooner or later, and to provide the most efficient path to ground when it happens. A well grounded mast DOES NOT attract lightning any better than a non grounded mast at the same location. That's horse caca, and the OP can tell his friend I said so. They will stream the same, and I consider the chances of a direct strike about equal. It's when you actually take a strike is when the differences in grounding show up. The well grounded mast will take the charge to ground in an orderly military manner, and in most cases no damage will occur. The non grounded mast does not provide an orderly path to ground, so the strike takes whatever path has the least resistance. And even that path is likely to be fairly high resistance and fireworks are likely to occur. Houston, we have a problem.. :/ The OP did the proper thing by grounding his mast. If properly grounded, if he does take a strike, the mast will direct the charge to ground and little damage should occur. This does not mean you want a radio hooked up though. That takes extra measures like suppressors, ground window, star grounding, etc.. But at least he won't have to worry about burning the house down. I've had my mast directly struck more than once, and I had no damage at all. Period. But my feed lines were all grounded to my bulkhead outside the shack. I don't leave them connected as I use no suppressors. Two of those strikes were with me sitting in this chair 15 feet away from the base of the mast. You can actually hear the difference between a strike to a well grounded mast, and a strike to a poorly grounded object. The strike to the well grounded mast will be very quiet. Just an arc sound like throwing a light bulb on the ground. A strike to something poorly grounded like say a tree will be much louder. More like a crack from a shotgun. :( This is not to be confused with the overhead sonic boom which both types of strikes will make. I'm just talking about the local sound. Anyway, that's my $12.47 worth from someone that lives in lightning country and has taken multiple direct strikes though the years. If the OP wants some good lightning info, try searching for Gary Coffman and lightning on google. I don't know if his past posts are still archived, but they should be. He had a lot of good posts on various aspects of lightning protection. |
Ground antenna?
Dave wrote:
Was talking with someone the other day and mentioned that I had just grounded the antenna (the mast, actually) to protect against lightning strikes, and they said that was not such a good idea because lightning is more likely to strike a path that goes straight to ground. Like many things, "it depends".. what else is near the antenna? From an electric field standpoint, whether it's actually physically connected to the ground isn't all that important. It's that it's a conductor sticking up, and that causes the field to change. As the surrounding E-field changes over a time span of milliseconds, a mast connected to the ground vs isolated will have a slightly different voltage distribution over time, but over long times, it's not much different. Now I am not sure what to do. Anyone have any input on this topic? Ideas are gratefully received... Thanks, Dave |
Ground antenna?
A well grounded mast DOES NOT attract lightning any
better than a non grounded mast at the same location. actually it does. both the ieee and cigre have been using lightning statistics data collected mostly from tall masts for many years. There are well known formulas used to calculate the number of strokes to a pole or power line, both include the height, and as height increases so does the number of strokes to the object. The height also skews the current distribution with higher structures more likely to get more high current strokes. |
Ground antenna?
Dave wrote:
A well grounded mast DOES NOT attract lightning any better than a non grounded mast at the same location. actually it does. both the ieee and cigre have been using lightning statistics data collected mostly from tall masts for many years. There are well known formulas used to calculate the number of strokes to a pole or power line, both include the height, and as height increases so does the number of strokes to the object. The height also skews the current distribution with higher structures more likely to get more high current strokes. But, is there a difference in strike rate between grounded and ungrounded towers of the same height. I would think that the difference would be very small, and smaller as the height gets bigger. Since the vast majority of commercial masts,towers,buildings used to collect the stats are probably grounded (Because the code requires it...), it might be hard to find decent data for "ungrounded" things. (for one thing, the equipment used to collect the strike data, until recently, probably measured the current spike on the grounding wire.. these days, you could use the RF lightning detection systems, and match up strike locations against structure locations) Maybe wooden poles? (which are only "sort of grounded") |
Ground antenna?
On Oct 16, 5:13*pm, Jim Lux wrote:
Dave wrote: A well grounded mast DOES NOT attract lightning any better than a non grounded mast at the same location. actually it does. *both the ieee and cigre have been using lightning statistics data collected mostly from tall masts for many years. There are well known formulas used to calculate the number of strokes to a pole or power line, both include the height, and as height increases so does the number of strokes to the object. *The height also skews the current distribution with higher structures more likely to get more high current strokes. But, is there a difference in strike rate between grounded and ungrounded towers of the same height. *I would think that the difference would be very small, and smaller as the height gets bigger. Since the vast majority of commercial masts,towers,buildings used to collect the stats are probably grounded (Because the code requires it...), it might be hard to find decent data for "ungrounded" things. (for one thing, the equipment used to collect the strike data, until recently, probably measured the current spike on the grounding wire.. these days, you could use the RF lightning detection systems, and match up strike locations against structure locations) Maybe wooden poles? (which are only "sort of grounded") 'sort of grounded' is as good as grounded. The current that builds up the charge to initiate the upward streamer is relatively small, that can be seen in the use of the high value resistors commonly used to 'bleed off' charge from antennas. instead of bleeding it off they are actually just equalizing it with the local ground potential, the same as happens on a 'properly' grounded tower/vertical. in most cases you won't find an amateur tower that isn't grounded one way or another anyway, even if a specific ground rod or other system isn't supplied at the base there is still a decent ground through the foundation. and if not then there is through any cable going up the tower that connects to a rotor or most antennas. it takes real work to really insulate a tower from ground in such a way that it would not allow charge attracted to the area under a downward leader from moving up the tower... the large rf isolators and tower lighting isolators used on base insulated AM broadcast towers are a good example... and even on those types of towers you will hear reports of 'lots of snapping and popping' before a stroke, those sounds are small flashovers of the guy wire insulators as the charge flows up them toward the tower. So to do it right would mean using insulating guys also. Then, even if you got that far a tower of any height would end up going into corona at the bottom and top anyway due to the high vertical electric fields under a storm cloud... even if the corona didn't reach nearby ground conductors it would still collect/dissipate charge on the conducting vertical section which may still initiate a streamer. So the short answer is that i have not seen any comparison between grounded and ungrounded vertical structures. |
Ground antenna?
On Oct 16, 12:13*pm, Jim Lux wrote:
Dave wrote: A well grounded mast DOES NOT attract lightning any better than a non grounded mast at the same location. actually it does. *both the ieee and cigre have been using lightning statistics data collected mostly from tall masts for many years. There are well known formulas used to calculate the number of strokes to a pole or power line, both include the height, and as height increases so does the number of strokes to the object. *The height also skews the current distribution with higher structures more likely to get more high current strokes. But, is there a difference in strike rate between grounded and ungrounded towers of the same height. *I would think that the difference would be very small, and smaller as the height gets bigger. That's what I'm thinking. I know my well grounded mast is not a lightning magnet. Some years I get no strikes to it. In fact, I think it's been a few since the last one. Well, unless it was hit when I was not at home. I'm still of the opinion that the ability of an object to stream means more than if it's grounded or not. Airplanes are not grounded, and they get popped all the time. Trees are poorly grounded, and they get popped all the time. I've known quite a few people over the years that stuck a vertical on their roof and didn't ground it, and they got popped. Blew the ungrounded antenna to smithereens too.. Many golfers get popped on the golf course and they are not really grounded too well unless they are wearing spikes on their shoes. :/ I think the height of the object relative to it's surroundings, and it's ability to stream mean more than anything. Trees are a target lightning pick probably as much as anything, and most are fairly poorly grounded due to being wood with some moisture to helps things a bit. I think the trees ability to stream well is why they get picked on so often. The pointy ends of a leaf stream well, much like the pointy hairs on the head of a golfer. And when you have hundreds of leaves on a tree... :( But lets say a grounded mast does get struck slightly more than an ungrounded mast. That would not a logical reason to avoid grounding it, when the act of grounding the mast pretty much negates the likelihood of a strike doing much damage to the mast or the building next to, or under it. A wooden mast would act much the same as a tree if it did not have any kind of ground wire running along it's length. That's why I never use wood masts here. I'd rather have a grounded mast struck every 5 years with no damage, vs an ungrounded mast struck every 10 years that led to heavy damage or even burned the house down. So worrying about that is kind of silly I think, when you know an ungrounded mast is big trouble if it ever does get hit. |
Ground antenna?
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Ground antenna?
wrote in message ... On Oct 15, 10:54 am, Ian Jackson wrote: One reason for lightning conductors (and for grounding elevated conductors, like radio antennas) is that it helps to stop a high electrostatic charge from accumulating in the air immediately above them. The intention is to PREVENT a direct lightning strike, rather than conduct a strike to ground. Of course, if a direct strike DOES occur, an antenna (and even a stout lightning conductor) may be seriously damaged. -- Ian "The only problem with that is that the charge is so quickly replenished that I think trying to bleed off the charge is a waste of time." The turn of the century genius, Testla, patented some lighting protection devices based on having an insulated "cap" at the highest object on the protected property. The "cap" would rise thousands of volts above the protected structure and this would reduce the tendency of lightning to strike. Seems to me that the federal government has lots and lots of buildings and would relatively inexpensively conduct definitive experiments to see what works and what doesn't in the area of lightning protection. So far as I know, the feds have done no such thing. |
Ground antenna?
On Oct 16, 8:55*pm, "John Gilmer" wrote:
wrote in message ... On Oct 15, 10:54 am, Ian Jackson wrote: One reason for lightning conductors (and for grounding elevated conductors, like radio antennas) is that it helps to stop a high electrostatic charge from accumulating in the air immediately above them. The intention is to PREVENT a direct lightning strike, rather than conduct a strike to ground. Of course, if a direct strike DOES occur, an antenna (and even a stout lightning conductor) may be seriously damaged.. -- Ian "The only problem with that is that the charge is so quickly replenished that I think trying to bleed off the charge is a waste of time." The turn of the century genius, Testla, patented some lighting protection devices based on having an insulated "cap" at the highest object on the protected property. * The "cap" would rise thousands of volts above the protected structure and this would reduce the tendency of lightning to strike. Seems to me that the federal government has lots and lots of buildings and would relatively inexpensively conduct definitive experiments to see what works and what doesn't in the area of lightning protection. So far as I know, the feds have done no such thing. yes, they have, not that i believe everything the government has said, but this stuff i do. this presentation lists several reports by the navy and faa among other agencies: http://www.docstoc.com/docs/4177489/...-Abdul-M-Mousa the nfpa and others are quoted here, even though the author is skeptical: http://www.straightdope.com/columns/...-strikes-again this one again quotes the onr, nasa, and air force studies as well as others. http://lightning-protection-institut...ct-fallacy.htm as far as tesla's stuff, i file it with most of the other experiments with lightning protection and prevention, if it really worked it would be used all over the place. the only system that has stood the test of time is the old franklin rod system, it doesn't prevent strikes, but it does try to provide a safe route to ground besides through the protected structure. much of the success of it depends on the quality of the installer, mostly how well they bond the various wires and how well they take it to ground. |
Ground antenna?
John Gilmer wrote:
wrote in message ... On Oct 15, 10:54 am, Ian Jackson wrote: One reason for lightning conductors (and for grounding elevated conductors, like radio antennas) is that it helps to stop a high electrostatic charge from accumulating in the air immediately above them. The intention is to PREVENT a direct lightning strike, rather than conduct a strike to ground. Of course, if a direct strike DOES occur, an antenna (and even a stout lightning conductor) may be seriously damaged. -- Ian "The only problem with that is that the charge is so quickly replenished that I think trying to bleed off the charge is a waste of time." The turn of the century genius, Testla, patented some lighting protection devices based on having an insulated "cap" at the highest object on the protected property. The "cap" would rise thousands of volts above the protected structure and this would reduce the tendency of lightning to strike. This is done in some HV test laboratories to avoid flashover to the ceiling and to make the field more representative of "outdoors".. they hang a semiconductive curtain in a horizontal plane above the apparatus which charges up and makes what's above look less like "ground" There's also the whole thing of surrounding a valuable structure (e.g. ammunition storage bunker, rocket launch pad) with an array of high towers with grounded wires from the tops of the towers. While no guarantee that lightning won't strike elsewhere, it definitely ups the odds of the protective structure taking the hit. here's a pictu http://commons.wikimedia.org/wiki/Fi...launch_pad.jpg |
Ground antenna?
On Oct 16, 10:43*pm, Jim Lux wrote:
John Gilmer wrote: wrote in message ... On Oct 15, 10:54 am, Ian Jackson wrote: One reason for lightning conductors (and for grounding elevated conductors, like radio antennas) is that it helps to stop a high electrostatic charge from accumulating in the air immediately above them. The intention is to PREVENT a direct lightning strike, rather than conduct a strike to ground. Of course, if a direct strike DOES occur, an antenna (and even a stout lightning conductor) may be seriously damaged. -- Ian "The only problem with that is that the charge is so quickly replenished that I think trying to bleed off the charge is a waste of time." The turn of the century genius, Testla, patented some lighting protection devices based on having an insulated "cap" at the highest object on the protected property. * The "cap" would rise thousands of volts above the protected structure and this would reduce the tendency of lightning to strike. This is done in some HV test laboratories to avoid flashover to the ceiling and to make the field more representative of "outdoors".. they hang a semiconductive curtain in a horizontal plane above the apparatus which charges up and makes what's above look less like "ground" There's also the whole thing of surrounding a valuable structure (e.g. ammunition storage bunker, rocket launch pad) with an array of high towers with grounded wires from the tops of the towers. *While no guarantee that lightning won't strike elsewhere, it definitely ups the odds of the protective structure taking the hit. here's a pictuhttp://commons.wikimedia.org/wiki/Fi...aunch_pad.jpg- Hide quoted text - - Show quoted text - yeah, the nasa pads have towers and long sloped wires to try to catch lightning also. for hv work we mostly do it outside or in a very tall building (the octagonal one just left of center in the top picture is open inside and about 80' tall. http://www.ewh.ieee.org/r1/schenecta...2007_lenox.pdf |
Ground antenna?
"Richard Clark" wrote ... On Fri, 16 Oct 2009 12:27:02 -0700 (PDT), wrote: I think the height of the object relative to it's surroundings, and it's ability to stream mean more than anything. Hi Mark, There's another angle to be observed here. Globally, there is a potential difference between earth and sky that runs to several hundred volts per meter, The Earth has the excess of electrons. The Earth produce the electric field about one hundred volts per meter. In a suuny day the electrons migrate up with the heavy ions (aggregates of H2O molecukes). with a current flow on the order of femtoAmperes per square cM. Not much locally, but for the full surface area of earth it is the electron conveyor belt charging the clouds through dust migration. This "electron conveyor belt" charge the air. Next the air becomes cooler and the condensation take place. Clouds appear. The condensation cause the voltage rise. All types of sparks jump. Under clouds the electric field has the opposite direction and thousands volts per meter. At this potential and current, absolutely everything is a short circuit that penetrates the voltage isoclines raising earth towards the clouds. The high voltagi in the clouds is lowered by the "electron conveyor belt" and the lightning. The "electron conveyor belt" is more effective if the Earth have many sharp needle. So there are the two possibilities: 1. If "The intention is to PREVENT a direct lightning strike," - many sharp needle is used, 2. If the intention is to CATCH a direct lightning strike and conduct a strike to ground - a polished big ball is used. S* |
Ground antenna?
In message , Szczepan Bialek
writes "Richard Clark" wrote .. . On Fri, 16 Oct 2009 12:27:02 -0700 (PDT), wrote: I think the height of the object relative to it's surroundings, and it's ability to stream mean more than anything. Hi Mark, There's another angle to be observed here. Globally, there is a potential difference between earth and sky that runs to several hundred volts per meter, The Earth has the excess of electrons. The Earth produce the electric field about one hundred volts per meter. In a suuny day the electrons migrate up with the heavy ions (aggregates of H2O molecukes). with a current flow on the order of femtoAmperes per square cM. Not much locally, but for the full surface area of earth it is the electron conveyor belt charging the clouds through dust migration. This "electron conveyor belt" charge the air. Next the air becomes cooler and the condensation take place. Clouds appear. The condensation cause the voltage rise. All types of sparks jump. Under clouds the electric field has the opposite direction and thousands volts per meter. At this potential and current, absolutely everything is a short circuit that penetrates the voltage isoclines raising earth towards the clouds. The high voltagi in the clouds is lowered by the "electron conveyor belt" and the lightning. The "electron conveyor belt" is more effective if the Earth have many sharp needle. So there are the two possibilities: 1. If "The intention is to PREVENT a direct lightning strike," - many sharp needle is used, 2. If the intention is to CATCH a direct lightning strike and conduct a strike to ground - a polished big ball is used. S* In the early days of lightning conductors, I believe that the French didn't like the nasty pointy things which the British had installed. Instead, they decorated theirs with fancy balls at the top - with sometimes disastrous results. -- Ian |
Ground antenna?
"Ian Jackson" wrote ... In message , Szczepan Bialek writes "Richard Clark" wrote . .. On Fri, 16 Oct 2009 12:27:02 -0700 (PDT), wrote: I think the height of the object relative to it's surroundings, and it's ability to stream mean more than anything. Hi Mark, There's another angle to be observed here. Globally, there is a potential difference between earth and sky that runs to several hundred volts per meter, The Earth has the excess of electrons. The Earth produce the electric field about one hundred volts per meter. In a suuny day the electrons migrate up with the heavy ions (aggregates of H2O molecukes). with a current flow on the order of femtoAmperes per square cM. Not much locally, but for the full surface area of earth it is the electron conveyor belt charging the clouds through dust migration. This "electron conveyor belt" charge the air. Next the air becomes cooler and the condensation take place. Clouds appear. The condensation cause the voltage rise. All types of sparks jump. Under clouds the electric field has the opposite direction and thousands volts per meter. At this potential and current, absolutely everything is a short circuit that penetrates the voltage isoclines raising earth towards the clouds. The high voltagi in the clouds is lowered by the "electron conveyor belt" and the lightning. The "electron conveyor belt" is more effective if the Earth have many sharp needle. So there are the two possibilities: 1. If "The intention is to PREVENT a direct lightning strike," - many sharp needle is used, 2. If the intention is to CATCH a direct lightning strike and conduct a strike to ground - a polished big ball is used. S* In the early days of lightning conductors, I believe that the French didn't like the nasty pointy things which the British had installed. Instead, they decorated theirs with fancy balls at the top - with sometimes disastrous results. Now everywhere are "the nasty pointy things" but most people do not know why and if they PREVENT or CATCH. S* |
Ground antenna?
On Oct 21, 2:49*am, "Szczepan Bialek" wrote:
1. If *"The intention is to PREVENT a direct lightning strike," - many sharp needle is used, Good luck. 2. If the intention is to CATCH a direct lightning strike and *conduct a strike to ground - a polished big ball is used. S* Good luck. |
Ground antenna?
wrote ... On Oct 21, 2:49 am, "Szczepan Bialek" wrote: 1. If "The intention is to PREVENT a direct lightning strike," - many sharp needle is used, Good luck. 2. If the intention is to CATCH a direct lightning strike and conduct a strike to ground - a polished big ball is used. S* Good luck. The above apply to grounded tower. For: " But, is there a difference in strike rate between grounded and ungrounded towers of the same height. I would think that the difference would be very small, and smaller as the height gets bigger." You wrote: "I'd rather have a grounded mast struck every 5 years with no damage, vs an ungrounded mast struck every 10 years that led to heavy damage or even burned the house down. So worrying about that is kind of silly I think, when you know an ungrounded mast is big trouble if it ever does get hit." The grounded tower catch the electrons in form of "electron conveyer belt" and lightning. If the "belt" is efective enough no lightnings. All local exces of electrons from the cloud flow without lightning. If no the lightning appears but it is weak (the sum of electrons is the same). The strike in the ungrouded tower is always strong. So You are right. S* |
Ground antenna?
On Oct 22, 8:40*am, "Szczepan Bialek" wrote:
... On Oct 21, 2:49 am, "Szczepan Bialek" wrote: 1. If "The intention is to PREVENT a direct lightning strike," - many sharp needle is used, Good luck. 2. If the intention is to CATCH a direct lightning strike and conduct a strike to ground - a polished big ball is used. S* Good luck. The above apply to grounded tower. For: " But, is there a difference in strike rate between grounded and ungrounded towers of the same height. I would think that the difference would be very small, and smaller as the height gets bigger." You wrote: "I'd rather have a grounded mast struck every 5 years with no damage, vs an ungrounded mast struck every 10 years that led to heavy damage or even burned the house down. So worrying about that is kind of silly I think, when you know an ungrounded mast is big trouble if it ever does get hit." The grounded tower catch the electrons in form of "electron conveyer belt" and lightning. If the "belt" is efective enough no lightnings. All local exces of electrons from the cloud flow without lightning. If no the lightning appears but it is weak (the sum of electrons is the same). The strike in the ungrouded tower is always strong. So You are right. S* no, that is not right. a grounded tower can not dissipate enough charge to reduce the stroke intensity. towers actually attract MORE high current strokes than the surrounding ground. |
Ground antenna?
Dave wrote:
On Oct 22, 8:40 am, "Szczepan Bialek" wrote: You wrote: "I'd rather have a grounded mast struck every 5 years with no damage, vs an ungrounded mast struck every 10 years that led to heavy damage or even burned the house down. So worrying about that is kind of silly I think, when you know an ungrounded mast is big trouble if it ever does get hit." The grounded tower catch the electrons in form of "electron conveyer belt" and lightning. If the "belt" is efective enough no lightnings. All local exces of electrons from the cloud flow without lightning. If no the lightning appears but it is weak (the sum of electrons is the same). The strike in the ungrouded tower is always strong. So You are right. S* no, that is not right. a grounded tower can not dissipate enough charge to reduce the stroke intensity. towers actually attract MORE high current strokes than the surrounding ground. Well, Szechuan obviously hasn't figured out which way the belt is pumping electrons, so it's not surprising he's wrong. He also doesn't understand anything of the physics involved, either, so none of his nonsensical answers should be a surprise. tom K0TAR* |
Ground antenna?
"Dave" wrote ... On Oct 22, 8:40 am, "Szczepan Bialek" wrote: ... On Oct 21, 2:49 am, "Szczepan Bialek" wrote: 1. If "The intention is to PREVENT a direct lightning strike," - many sharp needle is used, Good luck. 2. If the intention is to CATCH a direct lightning strike and conduct a strike to ground - a polished big ball is used. S* Good luck. The above apply to grounded tower. For: " But, is there a difference in strike rate between grounded and ungrounded towers of the same height. I would think that the difference would be very small, and smaller as the height gets bigger." You wrote: "I'd rather have a grounded mast struck every 5 years with no damage, vs an ungrounded mast struck every 10 years that led to heavy damage or even burned the house down. So worrying about that is kind of silly I think, when you know an ungrounded mast is big trouble if it ever does get hit." The grounded tower catch the electrons in form of "electron conveyer belt" and lightning. If the "belt" is efective enough no lightnings. All local excess of electrons from the cloud flow without lightning. If no, the lightning appears but it is weak (the sum of electrons is the same). The strike in the ungrouded tower is always strong. So You are right. S* no, that is not right. a grounded tower can not dissipate enough charge to reduce the stroke intensity. towers actually attract MORE high current strokes than the surrounding ground. Grounded towers with the many spikes dissipate more charge then the simmilar towers with the polished big ball. That with the many spikes PREVENT (or minimalise), that with the balls CATCH (high current strokes). |
Ground antenna?
"tom" wrote . net... Dave wrote: On Oct 22, 8:40 am, "Szczepan Bialek" wrote: You wrote: "I'd rather have a grounded mast struck every 5 years with no damage, vs an ungrounded mast struck every 10 years that led to heavy damage or even burned the house down. So worrying about that is kind of silly I think, when you know an ungrounded mast is big trouble if it ever does get hit." The grounded tower catch the electrons in form of "electron conveyer belt" and lightning. If the "belt" is efective enough no lightnings. All local excess of electrons from the cloud flow without lightning. If no, the lightning appears but it is weak (the sum of electrons is the same). The strike in the ungrouded tower is always strong. So You are right. S* no, that is not right. a grounded tower can not dissipate enough charge to reduce the stroke intensity. towers actually attract MORE high current strokes than the surrounding ground. Well, Szechuan obviously hasn't figured out which way the belt is pumping electrons, so it's not surprising he's wrong. He also doesn't understand anything of the physics involved, either, so none of his nonsensical answers should be a surprise. The atmospheric electricity was described in XIX century. At that time Armstrong and Kelvin build the High Voltage Generators (steam and drop). Also the way how the spikes work. Have you the old books? S* S* |
Ground antenna?
In article ,
"Szczepan Bialek" wrote: "Dave" wrote ... On Oct 22, 8:40 am, "Szczepan Bialek" wrote: . .. On Oct 21, 2:49 am, "Szczepan Bialek" wrote: 1. If "The intention is to PREVENT a direct lightning strike," - many sharp needle is used, Good luck. 2. If the intention is to CATCH a direct lightning strike and conduct a strike to ground - a polished big ball is used. S* Good luck. The above apply to grounded tower. For: " But, is there a difference in strike rate between grounded and ungrounded towers of the same height. I would think that the difference would be very small, and smaller as the height gets bigger." You wrote: "I'd rather have a grounded mast struck every 5 years with no damage, vs an ungrounded mast struck every 10 years that led to heavy damage or even burned the house down. So worrying about that is kind of silly I think, when you know an ungrounded mast is big trouble if it ever does get hit." The grounded tower catch the electrons in form of "electron conveyer belt" and lightning. If the "belt" is efective enough no lightnings. All local excess of electrons from the cloud flow without lightning. If no, the lightning appears but it is weak (the sum of electrons is the same). The strike in the ungrouded tower is always strong. So You are right. S* no, that is not right. a grounded tower can not dissipate enough charge to reduce the stroke intensity. towers actually attract MORE high current strokes than the surrounding ground. Grounded towers with the many spikes dissipate more charge then the simmilar towers with the polished big ball. That with the many spikes PREVENT (or minimalise), that with the balls CATCH (high current strokes). Much of this is speculation. With 10 million volts; currents of 10,000 amperes and strokes that can travel 30 miles: whether you have a ball or a spike on top of a roof isn't going to make much difference. It has been shown that a properly installed lightning rod system; and UL rated materials connected to low resistance grounds will increase the odds of protecting lives and property substantially. (The TV stations on top the Sears tower in Chicago continue to transmit even as they are being struck.) |
Ground antenna?
On Oct 23, 8:03*am, "Szczepan Bialek" wrote:
"tom" ouse.net... Dave wrote: On Oct 22, 8:40 am, "Szczepan Bialek" wrote: You wrote: "I'd rather have a grounded mast struck every 5 years with no damage, vs an ungrounded mast struck every 10 years that led to heavy damage or even burned the house down. So worrying about that is kind of silly I think, when you know an ungrounded mast is big trouble if it ever does get hit." The grounded tower catch the electrons in form of "electron conveyer belt" and lightning. If the "belt" is efective enough no lightnings. All local excess of electrons from the cloud flow without lightning. If no, the lightning appears but it is weak (the sum of electrons is the same). The strike in the ungrouded tower is always strong. So You are right. S* no, that is not right. *a grounded tower can not dissipate enough charge to reduce the stroke intensity. *towers actually attract MORE high current strokes than the surrounding ground. Well, Szechuan obviously hasn't figured out which way the belt is pumping electrons, so it's not surprising he's wrong. *He also doesn't understand anything of the physics involved, either, so none of his nonsensical answers should be a surprise. The atmospheric electricity was described in XIX century. At that time Armstrong and Kelvin build the High Voltage Generators (steam and drop). Also the way how the spikes work. Have you the old books? S* S*- Hide quoted text - - Show quoted text - I find that the new books have the good information that has been well proved over the last 100 years or so. There were lots of theories in those old books that have been proved false over the years. It also helps to work in the field, at the hv lab i work at we can run 3 phase 765kv, +/- 1Mv dc, and about 5Mv pulses. one of my personal jobs is writing software for lightning protection design on hv power lines, so i have been through this stuff many times. |
Ground antenna?
wrote ... In article , "Szczepan Bialek" wrote: Grounded towers with the many spikes dissipate more charge then the simmilar towers with the polished big ball. That with the many spikes PREVENT (or minimalise), that with the balls CATCH (high current strokes). Much of this is speculation. It is a history: "In the early days of lightning conductors, I believe that the French didn't like the nasty pointy things which the British had installed. Instead, they decorated theirs with fancy balls at the top - with sometimes disastrous results. -- Ian" With 10 million volts; currents of 10,000 amperes and strokes that can travel 30 miles: whether you have a ball or a spike on top of a roof isn't going to make much difference. The volts appear when no chance to dissipation. To have it on the roof must be multiplicity of spikes (not one). It has been shown that a properly installed lightning rod system; and UL rated materials connected to low resistance grounds will increase the odds of protecting lives and property substantially. (The TV stations on top the Sears tower in Chicago continue to transmit even as they are being struck.) All is true. I only wanted to add something about the spikes and balls. It was nice that Ian support me with the funny anecdote. S* |
Ground antenna?
"Dave" wrote ... On Oct 23, 8:03 am, "Szczepan Bialek" wrote: The atmospheric electricity was described in XIX century. At that time Armstrong and Kelvin build the High Voltage Generators (steam and drop). Also the way how the spikes work. Have you the old books? S* - Show quoted text - I find that the new books have the good information that has been well proved over the last 100 years or so. There were lots of theories in those old books that have been proved false over the years. It also helps to work in the field, at the hv lab i work at we can run 3 phase 765kv, +/- 1Mv dc, and about 5Mv pulses. one of my personal jobs is writing software for lightning protection design on hv power lines, so i have been through this stuff many times. Tell us than what do you use: Plenty of spikes or balls? S* |
Ground antenna?
Szczepan Białek wrote:
It is a history: "In the early days of lightning conductors, I believe that the French didn't like the nasty pointy things which the British had installed. Instead, they decorated theirs with fancy balls at the top - with sometimes disastrous results. I assume a certain biased reporting of anecdotal evidence.:-) A ball at the top hat of a Tesla coil allows a greater amplitude of voltage to build up before arcing than does a point at the top. Therefo Points should result in more lightning strikes at lower voltages. Balls should result in fewer lightning strikes at lower voltages. Can't think of any valid reason why either design should be able to avoid the really big one. -- 73, Cecil, IEEE, OOTC, http://www.w5dxp.com |
Ground antenna?
In message , Cecil Moore
writes Szczepan Białek wrote: It is a history: "In the early days of lightning conductors, I believe that the French didn't like the nasty pointy things which the British had installed. Instead, they decorated theirs with fancy balls at the top - with sometimes disastrous results. I assume a certain biased reporting of anecdotal evidence.:-) A ball at the top hat of a Tesla coil allows a greater amplitude of voltage to build up before arcing than does a point at the top. Therefo Points should result in more lightning strikes at lower voltages. Balls should result in fewer lightning strikes at lower voltages. Did you mean 'higher'? Can't think of any valid reason why either design should be able to avoid the really big one. Surely, when lightning is about, points allow an essentially continuous discharge at a low current, while balls allow the voltage to build up and up, until there is a big 'splat'? -- Ian |
Ground antenna?
Ian Jackson wrote:
Cecil Moore writes Balls should result in fewer lightning strikes at lower voltages. Did you mean 'higher'? Two people separated by a common language? :-) Allow me to rephrase: When the voltages are low, the ball will tend to discourage the lightning strikes because the voltage may be too low to achieve the ionizing threshold potential surrounding the ball. -- 73, Cecil, IEEE, OOTC, http://www.w5dxp.com |
Ground antenna?
On Oct 23, 2:48*pm, Ian Jackson
wrote: In message , Cecil Moore writes Szczepan Białek wrote: It is a history: "In the early days of lightning conductors, I believe that the French didn't like the nasty pointy things which the British had installed. Instead, they decorated theirs with fancy balls at the top - with sometimes disastrous results. I assume a certain biased reporting of anecdotal evidence.:-) A ball at the top hat of a Tesla coil allows a greater amplitude of voltage to build up before arcing than does a point at the top. Therefo Points should result in more lightning strikes at lower voltages. Balls should result in fewer lightning strikes at lower voltages. Did you mean 'higher'? Can't think of any valid reason why either design should be able to avoid the really big one. Surely, when lightning is about, points allow an essentially continuous discharge at a low current, while balls allow the voltage to build up and up, until there is a big 'splat'? -- Ian In the end, that's about the way I see it, but I consider any discharge by either to really be fairly irrelevant. Trying to avoid strikes by discharge is like whizzing in a whirlwind. :/ The sharp point streams much easier than the ball, so the chances of streaming and connected to a down leader are much greater than with a ball which will resists streaming at those same potentials. If you had a spike next to a ball, I would think the spike would be struck most of the time. You need a good streamer going to lure a down leader. But a ball can still stream if the potential cranks up high enough, and the resulting strike can often be a a stout one if it can overcome the poor streaming of the smooth ball. Both masts should be well grounded. It's not an accident that most lightning rods have a sharp point, the same way as most flag poles have a round ball on top. One is designed to stream as well as possible in order to become a more likely target than what it protects, and the other is designed to stream poorly to resist strikes compared to the other better streaming objects near it. No streamer, no cloud to ground lightning at that point on the earth. BTW, I've got pictures of streamers. You can see them at night, and they bend and point to the down leader as it approaches the earth. The first one it can connect to forms the final path to ground, and I think this is in the last 150 yards or so if I remember right. The leader traveling in appx 150 yard or so steps through the sky. |
Ground antenna?
wrote ... On Oct 23, 2:48 pm, Ian Jackson wrote: In message , Cecil Moore writes Szczepan Białek wrote: It is a history: "In the early days of lightning conductors, I believe that the French didn't like the nasty pointy things which the British had installed. Instead, they decorated theirs with fancy balls at the top - with sometimes disastrous results. I assume a certain biased reporting of anecdotal evidence.:-) A ball at the top hat of a Tesla coil allows a greater amplitude of voltage to build up before arcing than does a point at the top. Therefo Points should result in more lightning strikes at lower voltages. Balls should result in fewer lightning strikes at lower voltages. Did you mean 'higher'? Can't think of any valid reason why either design should be able to avoid the really big one. Surely, when lightning is about, points allow an essentially continuous discharge at a low current, while balls allow the voltage to build up and up, until there is a big 'splat'? -- Ian In the end, that's about the way I see it, but I consider any discharge by either to really be fairly irrelevant. Trying to avoid strikes by discharge is like whizzing in a whirlwind. :/ The sharp point streams much easier than the ball, so the chances of streaming and connected to a down leader No down lider. Excess of electrons is in the stormcloud and they jumps if the difference of voltage exists. At first they jump inside cloud. Next they jump in the all directions outside cloud. But the all jumps are in form of oscillations. Lightnings produce LW. are much greater than with a ball which will resists streaming at those same potentials. If you had a spike next to a ball, I would think the spike would be struck most of the time. We need here the experimental data. Does anybody know? You need a good streamer going to lure a down leader. But a ball can still stream if the potential cranks up high enough, and the resulting strike can often be a a stout one if it can overcome the poor streaming of the smooth ball. The only cause for spark jump is the voltage difference. Spikes decrease it. Both masts should be well grounded. It's not an accident that most lightning rods have a sharp point, the same way as most flag poles have a round ball on top. Is the ball grounded? One is designed to stream as well as possible in order to become a more likely target than what it protects, and the other is designed to stream poorly to resist strikes compared to the other better streaming objects near it. Lightning (electrons) strike the Earth. Grounded ball has the voltage like the Earth. Nongrounded like the air. Such are neutral. Does not prevent and not catch. But may be attacked like all. No streamer, no cloud to ground lightning at that point on the earth. BTW, I've got pictures of streamers. You can see them at night, and they bend and point to the down leader as it approaches the earth. The first one it can connect to forms the final path to ground, and I think this is in the last 150 yards or so if I remember right. The leader traveling in appx 150 yard or so steps through the sky. The oscilations start from very short in all directions and the last steps are longest. S* |
Ground antenna?
On Oct 23, 6:23*pm, "Szczepan Bialek" wrote:
*"Dave" ... On Oct 23, 8:03 am, "Szczepan Bialek" wrote: The atmospheric electricity was described in XIX century. At that time Armstrong and Kelvin build the High Voltage Generators (steam and drop).. Also the way how the spikes work. Have you the old books? S* - Show quoted text - I find that the new books have the good information that has been well proved over the last 100 years or so. *There were lots of theories in those old books that have been proved false over the years. *It also helps to work in the field, at the hv lab i work at we can run 3 phase 765kv, +/- 1Mv dc, and about 5Mv pulses. *one of my personal jobs is writing software for lightning protection design on hv power lines, so i have been through this stuff many times. Tell us than what do you use: Plenty of spikes or balls? S* tall towers, well grounded. |
Ground antenna?
On Oct 24, 8:49*am, "Szczepan Bialek" wrote:
... On Oct 23, 2:48 pm, Ian Jackson wrote: In message , Cecil Moore writes Szczepan Białek wrote: It is a history: "In the early days of lightning conductors, I believe that the French didn't like the nasty pointy things which the British had installed. Instead, they decorated theirs with fancy balls at the top - with sometimes disastrous results. I assume a certain biased reporting of anecdotal evidence.:-) A ball at the top hat of a Tesla coil allows a greater amplitude of voltage to build up before arcing than does a point at the top. Therefo Points should result in more lightning strikes at lower voltages. Balls should result in fewer lightning strikes at lower voltages. Did you mean 'higher'? Can't think of any valid reason why either design should be able to avoid the really big one. Surely, when lightning is about, points allow an essentially continuous discharge at a low current, while balls allow the voltage to build up and up, until there is a big 'splat'? -- Ian In the end, that's about the way I see it, but I consider any discharge by either to really be fairly irrelevant. Trying to avoid strikes by discharge is like whizzing in a whirlwind. *:/ The sharp point streams much easier than the ball, so the chances of streaming and connected to a down leader No down lider. Excess of electrons is in the stormcloud and they jumps if the difference of voltage exists. At first they jump inside cloud. Next they jump in the all directions outside cloud. But the all jumps are in form of oscillations. Lightnings produce LW. yes, there are downward leaders. these can be tracked either by their radio noise or by radar. the size and step process has been well known for many years. are much greater than with a ball which will resists streaming at those same potentials. If you had a spike next to a ball, I would think the spike would be struck most of the time. and you think wrong. We need here the experimental data. Does anybody know? yes, but not you. You need a good streamer going to lure a down leader. But a ball can still stream if the potential cranks up high enough, and the resulting strike can often be a a stout one if it can overcome the poor streaming of the smooth ball. The only cause for spark jump is the voltage difference. Spikes decrease it. no they don't. they provide a better place for streamers to start because the sharp point increases the voltage gradient helping it to stream sooner. The oscilations start from very short in all directions and the last steps are longest. there are no oscillation in the step process. and there is no evidence that the steps change length in any report i have seen. |
Ground antenna?
"Dave" napisal w wiadomosci ... On Oct 24, 8:49 am, "Szczepan Bialek" wrote: ... The sharp point streams much easier than the ball, so the chances of streaming and connected to a down leader No down lider. Excess of electrons is in the stormcloud and they jumps if the difference of voltage exists. At first they jump inside cloud. Next they jump in the all directions outside cloud. But the all jumps are in form of oscillations. Lightnings produce LW. yes, there are downward leaders. these can be tracked either by their radio noise or by radar. the size and step process has been well known for many years. But the upwards liders are also possible. If downward lider oscillate close the high metal tower the electrons in the metal also oscillate and can jump out. But that are details. are much greater than with a ball which will resists streaming at those same potentials. If you had a spike next to a ball, I would think the spike would be struck most of the time. and you think wrong. We need here the experimental data. Does anybody know? yes, but not you. But I agre with you. Nm5k wrote the above: : "I would think the spike would be struck most of the time." You need a good streamer going to lure a down leader. But a ball can still stream if the potential cranks up high enough, and the resulting strike can often be a a stout one if it can overcome the poor streaming of the smooth ball. The only cause for spark jump is the voltage difference. Spikes decrease it. no they don't. they provide a better place for streamers to start because the sharp point increases the voltage gradient helping it to stream sooner. One sharp point provide a better place for streamers to start, but the plenty of them decrease the voltage. The oscilations start from very short in all directions and the last steps are longest. there are no oscillation in the step process. and there is no evidence that the steps change length in any report i have seen. But it is obvious. Each spark is in form of oscillations. No matter if the "electrods" are steady or the distance is increasing. It was discovered by observing the tissue punched by the spark (XIX century). In nowadays reports no obvious thinks. S* |
Ground antenna?
Szczepan Bialek wrote:
Excess of electrons is in the stormcloud and they jumps if the difference of voltage exists. http://www.sleepingearthed.com/pdf/E...lecSurface.pdf -- 73, Cecil, IEEE, OOTC, http://www.w5dxp.com |
Ground antenna?
On Oct 24, 5:12*pm, "Szczepan Bialek" wrote:
*"Dave" napisal w ... On Oct 24, 8:49 am, "Szczepan Bialek" wrote: ... The sharp point streams much easier than the ball, so the chances of streaming and connected to a down leader No down lider. Excess of electrons is in the stormcloud and they jumps if the difference of voltage exists. At first they jump inside cloud. Next they jump in the all directions outside cloud. But the all jumps are in form of oscillations. Lightnings produce LW. yes, there are downward leaders. *these can be tracked either by their radio noise or by radar. *the size and step process has been well known for many years. But the upwards liders are also possible. If downward lider oscillate close the high metal tower the electrons in the metal also oscillate and can jump out. But that are details. are much greater than with a ball which will resists streaming at those same potentials. If you had a spike next to a ball, I would think the spike would be struck most of the time. and you think wrong. We need here the experimental data. Does anybody know? yes, but not you. But I agre with you. Nm5k wrote the above: : "I would think the spike *would be struck most of the time." You need a good streamer going to lure a down leader. But a ball can still stream if the potential cranks up high enough, and the resulting strike can often be a a stout one if it can overcome the poor streaming of the smooth ball. The only cause for spark jump is the voltage difference. Spikes decrease it. no they don't. *they provide a better place for streamers to start because the sharp point increases the voltage gradient helping it to stream sooner. One sharp point provide a better place for streamers to start, but the plenty of them decrease the voltage. The oscilations start from very short in all directions and the last steps are longest. there are no oscillation in the step process. *and there is no evidence that the steps change length in any report i have seen. But it is obvious. Each spark is in form of oscillations. No matter if the "electrods" are steady or the distance is increasing. It was discovered by observing the tissue punched by the spark (XIX century). In nowadays reports no obvious thinks. S* it may be obvious to you, but that doesn't make it true. a spark is not a form of oscillation. and leaders are not sparks. sparks are a very specific phenomenon that is a very short lived breakdown over a short distance. leaders and streamers are long term conductive channels caused by a channel of charge accumulated in them and are progressive breakdowns over long distances. The physics are very different, but in neither are there oscillations. again you go back to ancient history, it is time you updated your reading list. |
Ground antenna?
"Cecil Moore" napisal w wiadomosci ... Szczepan Bialek wrote: Excess of electrons is in the stormcloud and they jumps if the difference of voltage exists. http://www.sleepingearthed.com/pdf/E...lecSurface.pdf This is with the full agreement with me (in fundamentals). It is not easy to read, with the understanding, the electric schemes (diagrams). Look at the page 3. The arrows represent the currents. So the electrons flow in opposite direction. So in sunny day they migrate up. Very up (18 km at equator). The next symbols are the "+" and "-". What they means on this scheme. Electrons migrate very up, but always on the droplets of water (heavy ions), so in the air is the excess of electrons if there are the heavy ions. But what the voltage is there? You remember: small drops - smal voltage (Kelvin's drops generator). Next cooling and condensation take place and larger droplets fall down. But on the larger drops the voltage is higher. The "+" and "-" on electric schemes are use to indicate the direction of the current flow. Electrons flow from "-" to "+". No matter how many electrons is. But that everywhere in the atmosphere is excess of electrons should be obvious for you now. You know that on the surface of the Earth is also always the excess of electrons. But the current flow " if the difference of voltage exists". Not elecricians think that "-" indicate the excess of electrons and "+" the deficit. Such is in physics. The scheme on the page 3 was drawn by electricians. Do you agree? (Richard asks: get it?) S* |
Ground antenna?
"Dave" wrote ... On Oct 24, 5:12 pm, "Szczepan Bialek" wrote: Lightnings produce LW. yes, there are downward leaders. these can be tracked either by their radio noise or by radar. the size and step process has been well known for many years. The oscilations start from very short in all directions and the last steps are longest. there are no oscillation in the step process. and there is no evidence that the steps change length in any report i have seen. But it is obvious. Each spark is in form of oscillations. No matter if the "electrods" are steady or the distance is increasing. It was discovered by observing the tissue punched by the spark (XIX century). In nowadays reports no obvious thinks. S* it may be obvious to you, but that doesn't make it true. a spark is not a form of oscillation. and leaders are not sparks. sparks are a very specific phenomenon that is a very short lived breakdown over a short distance. leaders and streamers are long term conductive channels caused by a channel of charge accumulated in them and are progressive breakdowns over long distances. The physics are very different, but in neither are there oscillations. again you go back to ancient history, it is time you updated your reading list. All breakdown are made by oscillating electrons. They work like the pneumatic hammer. When electron oscillate (like in the Kundt's tube) at the end the voltage is doubled and the next distance is progressed. " Lightnings produce LW. yes, there are downward leaders. these can be tracked either by their radio noise or by radar. the size and step process has been well known for many years" In ECM such initial oscillations are detected and the power is shut down before full breakdown. The electrons have mass and charge - they like oscyllate. They oscillate before the full breakdown and after to dissipate the full energy. In the channel are better conditions to oscillations than in the conductor. S* |
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