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Is lighting nuts?
I HAD a tower up on the north side of the house for about 15 years, it
, top out at about 100feet. I built a 'tilt over' that is 52 feet tall with a mast of about 25, = 77 give or take. been 'up' about 1.5 years and lighting has 'hit' it twice. One was higher, never hit, this one is lower, hit is there anything I can do to 'fix this'? Lost antennas, need to do 'something'. thanks in advance. cl 73 |
"CIL" wrote in message ... I HAD a tower up on the north side of the house for about 15 years, it , top out at about 100feet. I built a 'tilt over' that is 52 feet tall with a mast of about 25, = 77 give or take. been 'up' about 1.5 years and lighting has 'hit' it twice. One was higher, never hit, this one is lower, hit is there anything I can do to 'fix this'? Lost antennas, need to do 'something'. thanks in advance. cl 73 Lightning is Female. 20 million volts & 100 thousand Amps will do as it damm well pleases! |
Hi CIL
Where lightning will hit, if it hits, can almost be calculated with a fair degree of accuracy. We did a small project in a college class and made a scale model of a small city. We knew from past history some of the structures that were hit and where. From this knowledge we made balls of certain sizes so they would touch if sitting on the ground the place that was actually hit. We ended up with only 4 such balls, each a similar size factor to the others. On our scale model town we outlined in red lines the most likely places lightning would hit if it did hit in that area. Every strike since that time, up until the project was abandoned, has hit somewhere on the red lines we have drawn. One such line was on a small single story U-Stor-It building between two very tall radio station towers, that was assumed to be lightning proof due to it's location. It was hit and hit hard when neither tower was hit. We also indicated that if those towers were ever hit, the location on those towers where the lightning would hit them. Neither location was near the top either. Two small strikes to one of the towers were both within 1 foot of where our red line was indicated on the scale model. We were so successful in our project we thought for sure some agency would pick it up and make use of it. But long after I was at school there, the project was abandoned with something like a record of 94% accuracy on pinpointing areas where lightning can hit. TTUL Gary |
CIL wrote:
"---is there anything I can do to fix this?" Broadcasters have towers that are often struck by lightning. AM towers sit on base insulators which makes them vulnerable to static buildup too. Wind carries a static charge which falls out on the tower even when no lightning is present. The shape and positions of charged clouds are constantly changing, so lightning strikes can come from anywhere. The broadcaster starts his lightning protection at the tower top with a small lightning rod extending above and beyond the beacon to take the hit and avoid expensive repairs at the tower top. Tower guy insulators are doubled and tripled where they connect to the tower so that static breakdown occurs to the earth instead of at the tower. An air gap is installed across the base insulator to bypass a lightning hit to earth. Often a turn or two is made in the feed to the tower. This discourages lightning on the feedline and encourages breakdown of the gap across the insulator. A static drain choke is often added if needed to provide a d-c path between the tower and the earth. It is used to bleed off charge which might build to dangerous levels. "Lightning elimination" is a name given to mounting a large number of sharp points around a protected area in an attempt to drain the atmosphere of charge. The reviews are mixed. I`ve worked in several broadcast stations hit by lightning nearly every time a charged cloud passed by. None ever caused significant damage. Al of the stations had lighted towers but their tower lighting chokes kept lightning off the a-c power source. Berst regards, Richard Harrison, KB5WZI |
I HAD a tower up on the north side of the house for about 15 years, it , top out at about 100feet. I built a 'tilt over' that is 52 feet tall with a mast of about 25, = 77 give or take. been 'up' about 1.5 years and lighting has 'hit' it twice. One was higher, never hit, this one is lower, hit is there anything I can do to 'fix this'? Lost antennas, need to do 'something'. thanks in advance. cl 73 Can you describe how each tower was configured at the top and how it was grounded? What is important to know if the top ended up with sharp point (mast, VHF vertical antenna, etc.) or Yagi type antenna, like tribander etc. without anything pointy protruding above. Yuri, K3BU |
I would suspect a poor grounding system on the tower. If the ground is a
rod driven into the Earth, then the impedance needs to be as low as possible. Once the ground system takes a surge, glass crystalls will form in the dirt on and around the rod. The impedance then climbs and the number of strikes to the tower increase. The amount of impedance in your ground network determines the amount of static charge that can build on the tower and how fast the charge can bleed. The formula for calculating the bleed rate is 5 times (Resistance times Capacitance). The resistance is the ground impedance and the capacitance is the amount of surface area of the tower relative to the air flow over it (think of two plates on a capacitor with a dielectric between them). Any charge above that of the Earth makes that point more likely to get hit by lightning. The tower is only one item to concern yourself about because a floating antenna can be just as bad. Ground everything on the tower during a storm if it is not in operation such as a repeater. Surge arrestors on the antenna feeds then become imparative for repeater installations. A very large grounding system is required to mitigate the potential for lightning strikes on a tower. If a strike does occur, then the grounding structure needs to be able to dissipate the charge back into the Earth very quickly or the ground will be lost until the voltage on the ground falls. Again, R x C for the Earth. Good Luck, Frank N1SIF wrote in message ... I HAD a tower up on the north side of the house for about 15 years, it , top out at about 100feet. I built a 'tilt over' that is 52 feet tall with a mast of about 25, = 77 give or take. been 'up' about 1.5 years and lighting has 'hit' it twice. One was higher, never hit, this one is lower, hit is there anything I can do to 'fix this'? Lost antennas, need to do 'something'. thanks in advance. cl 73 |
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I would suspect a poor grounding system on the tower. If the ground is a rod driven into the Earth, then the impedance needs to be as low as possible. Once the ground system takes a surge, glass (( (crystalls?))) will formin the dirt on and around the rod. The impedance then climbs and the numberof strikes to the tower increase. The amount of impedance in your groundnetwork determines the amount of static charge that can build on the towerand how fast the charge can bleed. (((The tower sites are only about 100 feet apart, ground substance is the same, clay/rocks, 1st foot then clay…… The first tower ground, is a 4 ft hole, with ¾" rebar then driven deeper,1.5ft, w/ horz bars 1ft on center from bottom of hole to top, where a ¾ steel plate was welded to vertical bars, and to the plate, strong hinge plate connected to 25 rohn tower. The 'other site', is two 4" pipe, 5ft, in the ground, and welded to fence. Fence is 2"2/8 upset tubing that goes around property/everything welded. ((fence is 5 foot tall) and as stated part of the 'gournding system',,,? The first 'site' was not connected to the primenter fence,,problem???)) If you are familur with the ''bird tilting over and drinking from the cup", you can picture in your minds eye, my 'tilting tower'. It is about 75ft tall, with a uhf/vhf duel band at top of mast, four ft. below that is a two meter horz omni ground plane.))) Can you describe how each tower was configured at the top and how it was grounded? What is important to know if the top ended up with sharp point (mast, VHF vertical antenna, etc.) or Yagi type antenna, like tribander etc. without anything pointy protruding above. Yuri, K3BU ((( Both towers carried almost the same 'items', vhf/uhf , and 4 ft below that, clover leaf horz ground plane.))) but their tower lighting chokes kept lightning off the a-c power source. ((( What do you call these chokes, I know I have read about, but at the moment I am blank.))) The broadcaster starts his lightning protection at the tower top with a small lightning rod extending above and beyond the beacon to take the hit and avoid expensive repairs at the tower top. ((( Is this something like the antennas I have seen that have a 'center core' copper rod???))) Tower guy insulators are doubled and tripled where they connect to the tower so that static breakdown occurs to the earth instead of at the tower. ((( Where do I 'see/read' about this??))) One such line was on a small single story U-Stor-It building between two very tall radio station towers, that was assumed to be lightning proof due to it's location. It was hit and hit hard when neither tower was hit ……"How did your team "know" what was struck? """…my question was and is,,,, why? (((((((((((((((((((This statement is the one that makes the most sense to me))))))))))))))) Lightning is Female. 20 million volts & 100 thousand Amps will do as it damm well pleases! ((((Last, but not least,,,,,,, thank you, WILL implement input, cl&73)))) |
Sorry for the spelling error crystalls should be crystals. When lightning
hits the Earth, the heat it generates is enough to make glass which is an insulator. The ground rod becomes isolated from the Earth. If you spread out the contact area with the Earth as with the fence around the perimeter of the property, then the energy is not concentrated to one spot. The over all impedance is also much lower. I would install a ring grounding system around the tower. A 32ft. diameter ring would do nicely in a clay/rocky soil. Place 8ft. ground rods in the ground every 16 ft along the 32 ft. diameter circle (approx. 6 rods). Each rod is then connected to the tower base with a multistrand 00 copper wire and a ring of 00 copper to connect each rod together. The connections should be cad welded or at least treated with a deoxit coating to prevent corrosion. I have had excellent luck with this approach, no lightning hits and my tower sits up at 870ft. ASL or 650 ft. above average terrain. Note: the tower has a strike counter hooked up to it so I know no hits have happened. Go to this link to read more http://www.polyphaser.com/ppc_pen_home.asp . Frank N1SIF "CIL" wrote in message ... I would suspect a poor grounding system on the tower. If the ground is a rod driven into the Earth, then the impedance needs to be as low as possible. Once the ground system takes a surge, glass (( (crystalls?))) will formin the dirt on and around the rod. The impedance then climbs and the numberof strikes to the tower increase. The amount of impedance in your groundnetwork determines the amount of static charge that can build on the towerand how fast the charge can bleed. (((The tower sites are only about 100 feet apart, ground substance is the same, clay/rocks, 1st foot then clay.. The first tower ground, is a 4 ft hole, with ¾" rebar then driven deeper,1.5ft, w/ horz bars 1ft on center from bottom of hole to top, where a ¾ steel plate was welded to vertical bars, and to the plate, strong hinge plate connected to 25 rohn tower. The 'other site', is two 4" pipe, 5ft, in the ground, and welded to fence. Fence is 2"2/8 upset tubing that goes around property/everything welded. ((fence is 5 foot tall) and as stated part of the 'gournding system',,,? The first 'site' was not connected to the primenter fence,,problem???)) If you are familur with the ''bird tilting over and drinking from the cup", you can picture in your minds eye, my 'tilting tower'. It is about 75ft tall, with a uhf/vhf duel band at top of mast, four ft. below that is a two meter horz omni ground plane.))) Can you describe how each tower was configured at the top and how it was grounded? What is important to know if the top ended up with sharp point (mast, VHF vertical antenna, etc.) or Yagi type antenna, like tribander etc. without anything pointy protruding above. Yuri, K3BU ((( Both towers carried almost the same 'items', vhf/uhf , and 4 ft below that, clover leaf horz ground plane.))) but their tower lighting chokes kept lightning off the a-c power source. ((( What do you call these chokes, I know I have read about, but at the moment I am blank.))) The broadcaster starts his lightning protection at the tower top with a small lightning rod extending above and beyond the beacon to take the hit and avoid expensive repairs at the tower top. ((( Is this something like the antennas I have seen that have a 'center core' copper rod???))) Tower guy insulators are doubled and tripled where they connect to the tower so that static breakdown occurs to the earth instead of at the tower. ((( Where do I 'see/read' about this??))) One such line was on a small single story U-Stor-It building between two very tall radio station towers, that was assumed to be lightning proof due to it's location. It was hit and hit hard when neither tower was hit .."How did your team "know" what was struck? """.my question was and is,,,, why? (((((((((((((((((((This statement is the one that makes the most sense to me))))))))))))))) Lightning is Female. 20 million volts & 100 thousand Amps will do as it damm well pleases! ((((Last, but not least,,,,,,, thank you, WILL implement input, cl&73)))) |
The broadcaster starts his lightning protection at the tower top with a small lightning rod extending above and beyond the beacon to take the hit and avoid expensive repairs at the tower top. An air gap is installed across the base insulator to bypass a lightning hit to earth. Often a turn or two is made in the feed to the tower. This discourages lightning on the feedline and encourages breakdown of the gap across the insulator. We used to call em "johnny balls" at the base of the AM towers. One station I was chief engineer of was hit constantly without any damage. NOT fun to be in the transmitter room when lightning was hitting tho! I felt like Dr. Frankenstein in my lab during the storms, when I had to go into the xmitter room. A static drain choke is often added if needed to provide a d-c path between the tower and the earth. It is used to bleed off charge which might build to dangerous levels. A static drain choke is an EXCELLENT idea, I have used it on my ham antennas in the past. 73 WB7FFI |
"Gary V. Deutschmann, Sr." wrote Where lightning will hit, if it hits, can almost be calculated with a fair degree of accuracy. Gary, there is no nice way to say this, but I mean no disrespect to your experience. Unfortunately, what you wrote is absolutely incorrect, and flies in the face of thousands of lightning experts all over the world, who agree only that a 300' sphere rolled over a surface will indicate (by touching) the most likely points of attachment. This means that no taller object escapes the likelihood of being a point of attachment, period. It doesn't mean anything below it is free from side attachments and flashovers. Everything else you followed with was erroneous, based on misconceptions or complete falsehoods. Places you think lightning "struck", were more likely the opposite, the point(s) where it *left* a structure. Every once and awhile a new theory arrives claiming to predict or prevent lightning, and these have all been discredited, especially the CTS (Charge Transfer System) of lightning dissipators. There have been and there is no evidence whatsover that a point of attachment can be either predicted or prevented. This is even when the best lightning air terminal is in place at the highest point on a structure. Take your old notes and paper the bird cage, they offer only false predictions that cannot be replicated or withstand the studies that have tried this a hundred similar ways. You have left at your disposal, the ability to make it as easy as possible for a lightning attachment or near field effect from same, to be absorbed and routed via capable grounding and surge protection systems. There is nothing else newsworthy about it. We did a small project in a college class and made a scale model of a small city. We knew from past history some of the structures that were hit and where. From this knowledge we made balls of certain sizes so they would touch if sitting on the ground the place that was actually hit. We ended up with only 4 such balls, each a similar size factor to the others. On our scale model town we outlined in red lines the most likely places lightning would hit if it did hit in that area. Every strike since that time, up until the project was abandoned, has hit somewhere on the red lines we have drawn. One such line was on a small single story U-Stor-It building between two very tall radio station towers, that was assumed to be lightning proof due to it's location. It was hit and hit hard when neither tower was hit. We also indicated that if those towers were ever hit, the location on those towers where the lightning would hit them. Neither location was near the top either. Two small strikes to one of the towers were both within 1 foot of where our red line was indicated on the scale model. We were so successful in our project we thought for sure some agency would pick it up and make use of it. But long after I was at school there, the project was abandoned with something like a record of 94% accuracy on pinpointing areas where lightning can hit. TTUL Gary Jack Painter Virginia Beach VA http://members.cox.net/pc-usa/grounding.htm |
"CIL" wrote in message ... but their tower lighting chokes kept lightning off the a-c power source. ((( What do you call these chokes, I know I have read about, but at the moment I am blank.))) Perhaps you are thinking of an Austin Ring transformer to couple the power to the beacon lights........... |
CIL wrote:
"What do you call these chokes?" Tower lighting chokes. Every a-c power wire on most AM broadcast towers is fed through through a high-current r-f choke, beacon, side lights, and neutral. It avoids shorting out the tower at its base for the r-f signal. Another device is used at some stations for the same purpose. It is called an Austin transformer and consists linked loops to transfer a-c power while providing little r-f coupling. Tower lighting chokes must provide better performance for the price because they seem more prevalent. Tower lighting chokes may all be wraped around one form or on separate forms. They not only provide good r-f isolation, but they provide almost complete lightning isolation. They really keep lightning out of the a-c power circuits on the ground when used with appropriate bypass capacitors and arresters. Best regards, Richard Harrison, KB5WZI |
Grounding a tower does not help prevent it from getting hit by
lightning. It does however help route the charge safely to ground when hit. A tower may actually be a little less likely to be hit if not grounded but that is not a good thing to do. Placing ground rods out in a radius like the spokes of a wheel around a tower is a good thing. Placing a connecting wire between rods on the circle is a waste of wire. It would be better to use that additional wire for additional radials. The current will travel out away from the tower. Each ground lead going away from the tower will share the current. There is no significant current difference between the ground rods so the ring connection does no good. First a few ground rods should be placed as close to the tower as possible to have the shortest lead length from the tower. Additional ground rods placed on the "spokes" going out away from the tower at distances twice the rod lengths along each spoke. Having the connecting wires buried going to the other ground rods will increase the ground system effectiveness also. Not being struck because you have a good ground system is not proof that the ground system prevented it. 73 Gary K4FMX On Tue, 19 Oct 2004 16:15:04 -0400, "leaf" wrote: Sorry for the spelling error crystalls should be crystals. When lightning hits the Earth, the heat it generates is enough to make glass which is an insulator. The ground rod becomes isolated from the Earth. If you spread out the contact area with the Earth as with the fence around the perimeter of the property, then the energy is not concentrated to one spot. The over all impedance is also much lower. I would install a ring grounding system around the tower. A 32ft. diameter ring would do nicely in a clay/rocky soil. Place 8ft. ground rods in the ground every 16 ft along the 32 ft. diameter circle (approx. 6 rods). Each rod is then connected to the tower base with a multistrand 00 copper wire and a ring of 00 copper to connect each rod together. The connections should be cad welded or at least treated with a deoxit coating to prevent corrosion. I have had excellent luck with this approach, no lightning hits and my tower sits up at 870ft. ASL or 650 ft. above average terrain. Note: the tower has a strike counter hooked up to it so I know no hits have happened. Go to this link to read more http://www.polyphaser.com/ppc_pen_home.asp . Frank N1SIF "CIL" wrote in message .. . I would suspect a poor grounding system on the tower. If the ground is a rod driven into the Earth, then the impedance needs to be as low as possible. Once the ground system takes a surge, glass (( (crystalls?))) will formin the dirt on and around the rod. The impedance then climbs and the numberof strikes to the tower increase. The amount of impedance in your groundnetwork determines the amount of static charge that can build on the towerand how fast the charge can bleed. (((The tower sites are only about 100 feet apart, ground substance is the same, clay/rocks, 1st foot then clay.. The first tower ground, is a 4 ft hole, with ¾" rebar then driven deeper,1.5ft, w/ horz bars 1ft on center from bottom of hole to top, where a ¾ steel plate was welded to vertical bars, and to the plate, strong hinge plate connected to 25 rohn tower. The 'other site', is two 4" pipe, 5ft, in the ground, and welded to fence. Fence is 2"2/8 upset tubing that goes around property/everything welded. ((fence is 5 foot tall) and as stated part of the 'gournding system',,,? The first 'site' was not connected to the primenter fence,,problem???)) If you are familur with the ''bird tilting over and drinking from the cup", you can picture in your minds eye, my 'tilting tower'. It is about 75ft tall, with a uhf/vhf duel band at top of mast, four ft. below that is a two meter horz omni ground plane.))) Can you describe how each tower was configured at the top and how it was grounded? What is important to know if the top ended up with sharp point (mast, VHF vertical antenna, etc.) or Yagi type antenna, like tribander etc. without anything pointy protruding above. Yuri, K3BU ((( Both towers carried almost the same 'items', vhf/uhf , and 4 ft below that, clover leaf horz ground plane.))) but their tower lighting chokes kept lightning off the a-c power source. ((( What do you call these chokes, I know I have read about, but at the moment I am blank.))) The broadcaster starts his lightning protection at the tower top with a small lightning rod extending above and beyond the beacon to take the hit and avoid expensive repairs at the tower top. ((( Is this something like the antennas I have seen that have a 'center core' copper rod???))) Tower guy insulators are doubled and tripled where they connect to the tower so that static breakdown occurs to the earth instead of at the tower. ((( Where do I 'see/read' about this??))) One such line was on a small single story U-Stor-It building between two very tall radio station towers, that was assumed to be lightning proof due to it's location. It was hit and hit hard when neither tower was hit .."How did your team "know" what was struck? """.my question was and is,,,, why? (((((((((((((((((((This statement is the one that makes the most sense to me))))))))))))))) Lightning is Female. 20 million volts & 100 thousand Amps will do as it damm well pleases! ((((Last, but not least,,,,,,, thank you, WILL implement input, cl&73)))) |
Hi Jack
That is probably true and the reason the project was abandoned! Step Leaders can form and reach up from almost any grounded source, but more often than not, the eventual discharge causes no appreciable harm. The small study I helped with was some 25 or 30 years ago and I really don't remember too much of the details about it, other than apparent physical damage was almost always within our red zones. I don't think the spheres we were using were anywhere near 300 feet in diameter, if I recall they were like 36 feet, 72 feet and 108 feet. Regardless of the size of the ball, on most structures the red zone was in the same place. Only on very tall structures would the red zones be more than one zone at varying heights along the structure. I do remember our accuracy for the town we modeled was very high over 90%, but then too, we had a LOT of red zones as well since we were using like 5 different sizes of balls to mark these zones. You also have to remember, back when I was in Skewl, the correct answer to a question was considered WRONG. And the wrong answer correct. EG: Number of Elements, the WRONG answer the skewl demanded as correct was 45 Elements NO MORE NO LESS, and you had better not forget the NO MORE NO LESS phrase! There are 92 Natural Elements and about 114 Elements Maybe More. But if you put that on your exam, you were graded as the answer being WRONG. MOST of the stuff I learned in skewl was Erroneous in Real Life, I don't doubt that our lightning experiments were also! TTUL Gary |
Hi Richard
If you recall, I lost a tower to a lightning strike. Took us forever to figure out why it came down, but we finally did. Water built up in the leg of the tower, the lighting turned the water to steam causing the leg to explode. In some minor cases we found the places where lightning struck through burn and/or pit marks combined with visual observations of bystanders! Other times, the foot long melted out section of guttering was a dead giveaway along with the distortion of the rest of the guttering to ground. TTUL Gary |
"Gary V. Deutschmann, Sr." wrote Hi Jack That is probably true and the reason the project was abandoned! Step Leaders can form and reach up from almost any grounded source, but more often than not, the eventual discharge causes no appreciable harm. TTUL Gary Hi Gary, I understand completely. Lightning attaching to an object is not where the damage comes from, it's the way the damn stuff *leaves* that causes the problems! ;-) Notwithstanding your hopefully unique experience where water in a tower leg was superheated. Some private company specifications call for an air terminal and grounding electrode conductors on all their towers, including at each fixture (antenna) attachment point.. Even most tower manufacturers call this unnecessary, recommending bonding of air terminals (if used) to the tower legs only. But I suppose that a grounding electrode conductor from tower-top to ground *could* have prevented your loss, by reducing some of the current in the tower legs in favor of the heavy GEC coming down alongside them. Best regards, Jack |
These guys http://www.harger.com/ are the big boys in the lightning
protection business... Get this http://www.harger.com/equipcat.htm it will answer alot of questions. Also, see www.polyphaser.com I have towers at work that the tower crews say the air terminal is kept shiny from so many hits. N2QEW |
Gary Deutschmann wrote:
"If you recall, I lost a tower to a lightning strike." Yes. I was saddened by Gary`s misfortune.. My recollection of the event is that the tower was aluminum. It seems there may have been a poor electrical connection between tower sections which generated first great heat. There was a lightning induced failure of one of the tower legs, if I remember. The commercial towers erected by one of the companies I worked for, all had a copper cable about like a welding or jumper cable riunning the length of the tower, connecting the top plate to the ground system for the tower. Deep ground rods were connected to each tower leg. I encountered these towers upon joining the company. I would not have so specified those tower-length cables in those big steel towers, but it must have worked as we never had any lightning damage to the towers. In Gary`s case, such a cable might have prevented a melt-down. Best regards, Richard Harrison, KB5WZI |
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Hi Richard
I was just a lowly sophomore peon in a class of mostly upperclassmen who had started the project a few years before I went to skewl there. The project was a side assignment for extra credit that just seemed to carry on for all the years I was there and a few years thereafter. I was an avid model railroader quite adept at building miniature structures to emulate their full sized counterparts. This was my contribution to the project, the modeling end of it. When a new building was built in the town, I would make a scale model of it for the project layout board. I had to pay special attention to what objects of a structure consisted of metal components and how they were attached to the structure and if they led to a grounding source, as all of these factors played an important part in the experimentation that was going on. I knew what the project was about and what they were trying to prove with it. But I truly was not that interested in the purpose of the project as much as I was in the authenticity of detail in the structures used on the project layout board. In other words, I learned just enough to be dangerous in my observations, hi hi..... However, the success ratio of known lightning strikes to the red zones on our layout board was phenominal. The data was collected by a whole different team than the team I was on, but the layout board was loaded with bright orange lightning bolts glued to places of known lightning strikes and all but 2 of them were in our red zones. I should note that a red zone was simply a 1/8 to 1/4 inch wide line drawn on for example, the edges of gutters, at certain elevations on taller structures not shielded by another object. Naturally we did not know about many lightning strikes that did no damage or were not observed. My own antenna farm has been hit several times, but never was their any damage because of it. In fact, one year we had a strange phenomenon that caused neighbors to call the fire department on a couple occassions. One of my Yagi's appeared to have orange sparks flying from it, sometimes for as long as a half-hour, but usually only for a few seconds or minutes. I was only priviledged to see this myself in person one time. Scared the bejesus out of me when I did too! One of the firemen knew a man who worked on tall commercial chimneys or something like that and told him about it. The many came to my house, checked a few things out, talked to a couple of neighbors and showed them some photo's he had taken of a similar phenominon on other structures. Turns out what was happening was weather conditions and the charge in the air was just right to cause what was termed as St. Elmo's Fire, a phenominon discovered on old sailing ships at sea during a storm. I lived in that house roughly 20 years and this only happened for one short rainy season in only one of those years. I had never heard of a similar occurrance to ham antenna's before or after this event. And I've been licensed for 45 years! TTUL Gary |
Hi Jack
The damage to my tower was directly my own fault. It was of tubular aluminum construction and DID have drain holes in the legs so they could not readily fill with water. I made two very dumb mistakes that contributed to the damage. The first was using one of these holes for attaching the ground rod strap to the tower, instead of the clamp that WAS provided for the purpose. And the second was backfilling over these holes when a new air conditioner was installed, and a small retaining wall placed between the steps, tower and A/C unit. Had there not been water in the leg of the tower, it would have taken the hit unscathed. There was a grounding strap on each leg of the tower at the unions between sections, these were installed properly or should I say, per the instructions, hi hi..... Ironic, I was way overboard on everything else as far as protection from lightning. Had a copper bulkhead on the house, grounded of course. All coax shields were grounded first to the bulkhead and then through gas bottles which were also grounded. The station equipment was ground, even equipment in plastic cases I installed a ground to the chassis and they were grounded too. I did everything right except I forgot about one old abandoned rotor cable that was coiled up behind 4 file cabinets, out of sight out of mind. Luck of the Irish, the day I took the hit, I had sparks flying all over my shack. My pooch who was young then, terrified of thunder, came to my office to be by me for protection, just when the sparks began to fly. He never came into my office ever again! The only damage from this rotor wire was a few burn marks on the back of the file cabinets. The tower obviously took the main hit. As an aside. A tree outside my mothers home was struck by lighting. Split that sucker almost all the way to the ground. Dad bolted it back together with threaded rods and it survived, it's still living too. But the reason I brought it up is that INSIDE the house, sparks danced all over my mothers stainless steel kitchen sink, made burn marks and pits all over it. We later discovered the aerator on her faucet spout was fused to the spout and it too was severely burned and pitted. Back then all the waste lines to the sink were metal, not PVC as used today and all the water lines are copper. So I assume both the sink and the faucet were grounded. Makes one wonder how lightning got inside the house and bounced around in her sink and did enough damage that the sink and faucet had to be replaced. TTUL Gary |
Gary Deutschmann wrote:
"Turns out what was happening was weather conditions and the charge in the air was just right to cause what was called St. Elmo`s fire---." From my time in broadcast stations, I can testify these conditions repeat. In my experience, the radio towers took all the lightning strikes in the area. Charge buildup was a separate phenomenon.from lightning. This happened in the wind ahead of an approaching thunderstorm. The insulated guy segments would charge from the static in the air, announcing the approaching storm with loud reports when conditions were right. Peering out at the antennas disclosed flashes across the guy insulators producing the reports. There were many towers with many insulators which produced barrage fire. Noisy! Best regards, Richard Harrison, KB5WZI |
Hi Gary,
I did everything right except I forgot about one old abandoned rotor cable that was coiled up behind 4 file cabinets, out of sight out of mind. Luck of the Irish, the day I took the hit, I had sparks flying all over my shack. My pooch who was young then, terrified of thunder, came to my office to be by me for protection, just when the sparks began to fly. He never came into my office ever again! The only damage from this rotor wire was a few burn marks on the back of the file cabinets. The tower obviously took the main hit. A friend in Mobile, AL had several station equipments damaged this summer when protection was presumed to be "complete". Old cabling on the floor behind equipment racks was inductively charged and arced over to the equipment and computers, defeating the extensive surge protection installed. I had considered this a serious enugh problem to include it in a warning on my web page, and he was of course furious with himself about this since we had previously talked about it. This is also what I mean by the statement that lightning finds and exploits the weak parts of a system. As an aside. A tree outside my mothers home was struck by lighting. Split that sucker almost all the way to the ground. Dad bolted it back together with threaded rods and it survived, it's still living too. But the reason I brought it up is that INSIDE the house, sparks danced all over my mothers stainless steel kitchen sink, made burn marks and pits all over it. We later discovered the aerator on her faucet spout was fused to the spout and it too was severely burned and pitted. Back then all the waste lines to the sink were metal, not PVC as used today and all the water lines are copper. So I assume both the sink and the faucet were grounded. Makes one wonder how lightning got inside the house and bounced around in her sink and did enough damage that the sink and faucet had to be replaced. Could be either from an older home's cold water pipe grounding, or EMI from the nearby strike. The former is more likely, when ground becomes saturated with HV from a nearby strike, it raises the potential of everything connected to it. Nowadays this is called "GPR" or Ground Potental Rise. Possibly one of the biggest causes of damage to stations that are otherwise "protected". TTUL Gary Cheers, Jack |
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Hi Richard
Now 'that' I have seen a few times. Probably not to the extent that you have experienced though. When first out of skewl I took a job as a DJ, before a couple of storms while working in the transmitter room at the tower site, I could hear occasional pops, but never figured out where they were coming from. Thanks for letting me know! From my new residence I can see several radio and TV towers, I will keep an eye on them just out of curiosity sake. TTUL - 73+ de Gary - KGØZP |
Hi Jack
That was probably the cause! I figured the sink itself was at one ground potential and the faucet at another which caused the arcing. Of course, the way mom described it, one would think the whole sink was ablaze. Even back then I thought of possibly a single drop of hot metal (probably from the aerator) and how that is what probably bounced around in the sink sparking all over the place. Like dropped hot metal when your welding goes all over the place. Speaking of differing ground potentials. I think the wierdest thing I ever saw was when my step-son was taking me through the automated welding section of a body assembly plant for cars. A line of steel platforms bolted to a steel floor framework, between two of the platforms (about 2 to 3 inches apart) there was an occasional arc that occurred when the machines on each both stopped at the same time. Don't know if you remember the old vacuum powered windshield wipers that operated independent of each other. Every once in awhile they would be in sync for a few wipes. When these welders came into sync they hummed really loud and when the sync broke is when the arc would jump between their two stands. I thought it was interesting! TTUL Gary |
Hi Richard
Are you insinuating that a tree struck by lightning cannot live after being electrocuted? Although not logical, since the sap turning to steam is more than likely what split the tree in the first place. The path to ground could have been less than 1/4 inch wide on opposing sides of the tree. Nonetheless, the tree is still standing. It does have some strange areas of bulging bark where the crack used to be. I don't remember the exact year of the strike, but it was after 1968 and before 1972 and now this tree is the larger of the pair in moms backyard. It's immune system must have been damaged, because it has suffered from galls ever since shortly after it was split. Now, as far as bolting trees back together using threaded rods, this is not uncommon at all. The forked maple tree in my own front yard at my St. Louis QTH was bolted together in two places to keep the two trunks from spreading further as the tree grew. It worked! A cedar tree in my backyard that split during an ice storm was mended the same way at the same QTH. On this tree you can still see a part of some of the rods that were used. It only takes about 3 to 4 years for the large washer and nut to be covered with bark and depending upon the gap where the rods were placed, they may be visible for decades or covered in short order. TTUL Gary |
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Hi Richard
OK, I'll take it that way! YOU didn't know my father though, if it wasn't the way great grandpa did it, it wasn't done right, hi hi..... TTUL Gary |
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