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Lightning strike?
- Thread starter r carl
- Start date
Thanks. My bad tube is 5/8" OD and one end is formed to reduce the ID to 7/16" for the next tube.
Not necessarily true. I have seen lightning make antennas literally disappear. Antron 99 literally turned into fibreglass splinters all over the guys yard. Also seen wire antennas literally disappear. Neither were properly grounded. That is the issue where the antenna itself must handle the lightning current rather than the grounding.
Well thats a fiberglas rod, for sure that will blow. Wire acts like a fusible link and vaporizes. An aluminum antenna or VERY heavy gauge wire antenna will not blow up
I have a fond lightning memory.
A ham buddy from high school had made it to chief engineer at the big album-rock FM station in a town 90 miles away. Dropped in to visit the day after lightning had hit their FM antenna. The antenna was okay, but the 3-inch heliax had a 3-inch long hole blown in it, right where it made the 90-degree bend at ground level, leading to the transmitter. We fixed it with a hacksaw and 9 or 10 rolls of Scotch 33 electrical tape. Cut out the burned section and took the connection loose at the transmitter end. Fortunately there was some slack at ground level. We necked down the center conductor best we could, and made slots around the edge of the outer conductor. Threaded one end over the other, and twisted the 'outer' coax. It pulled itself over the 'inner' side several full turns. We judged this sufficient contact area to work for a while, and wrapped black tape around the splice. And wrapped. And wrapped.
Looked like poo, but the transmitter came back up, didn't complain about SWR. The splice wasn't getting hot to the touch.
Saved the station manager's bacon until the consulting engineer showed up and hired a crew to replace the heliax.
Once in a lifetime.
73
A ham buddy from high school had made it to chief engineer at the big album-rock FM station in a town 90 miles away. Dropped in to visit the day after lightning had hit their FM antenna. The antenna was okay, but the 3-inch heliax had a 3-inch long hole blown in it, right where it made the 90-degree bend at ground level, leading to the transmitter. We fixed it with a hacksaw and 9 or 10 rolls of Scotch 33 electrical tape. Cut out the burned section and took the connection loose at the transmitter end. Fortunately there was some slack at ground level. We necked down the center conductor best we could, and made slots around the edge of the outer conductor. Threaded one end over the other, and twisted the 'outer' coax. It pulled itself over the 'inner' side several full turns. We judged this sufficient contact area to work for a while, and wrapped black tape around the splice. And wrapped. And wrapped.
Looked like poo, but the transmitter came back up, didn't complain about SWR. The splice wasn't getting hot to the touch.
Saved the station manager's bacon until the consulting engineer showed up and hired a crew to replace the heliax.
Once in a lifetime.
73
Aluminum tubing like on a typical CB antenna can indeed be blown to hell and back. Again....it depends on whether the antenna was properly grounded or not. If the aluminum tubing has to handle all that current it will go by-by. I've seen a couple 1/2 or 5/8 wave groundplanes blown such that the only thing left were the radials and the mounting bracket. They were mounted on wooden poles with no ground wire. Typical 14 gauge antenna wire can melt but usually not the entire thing. It takes out a chunk somewhere. I've seen a lot of lightning strikes in my 43 years of playing radio and some survived beyond belief while others just disappeared.
Yeah the antennas would....or SHOULD survive no problem as most of the current should follow the tower to ground. Interesting that it blew in the elbow. My guess is the current flowed down the shield and arced to ground at the elbow which was the point where it presented higher opposition to current flow in the cable so it took the lazy route and took a shortcut to ground. That can happen easily if the cable is brought to ground level without a heavy ground strap just on the antenna side of the elbow. We used to bring all cables in just under an ice shield bridge about eight feet off the ground with the shields bonded to the tower at the point of curvature from vertical to horizontal. Never use an elbow at those points unless you absolutely have too for whatever reason.
Not all lightning strokes are created equal. I have seen portions of antennas just disappear. No shrapnel nearby, or identifiable chunks.
Always just assumed the metal had been turned to vapor, and went away. Well, the parts that didn't splatter onto nearby surfaces.
My granddad had a ham station on the family farm in Iowa in the early 1920s. In those days an antenna was the longest wire you could string, pretty much. Nobody worried about antenna resonance using a spark transmitter. The transmitter's output circuit was the antenna tuner.
He talked about a quarter-mile long wire antenna along the side of a corn field that was struck during a particularly strong storm. Said the whole quarter-mile of wire was just gone. No trace, except for one scorched piece about twelve feet long.
That antenna was connected to a ground rod when it was not on the air. Seems like it would have done a number to his station if it had been connected.
73
Always just assumed the metal had been turned to vapor, and went away. Well, the parts that didn't splatter onto nearby surfaces.
My granddad had a ham station on the family farm in Iowa in the early 1920s. In those days an antenna was the longest wire you could string, pretty much. Nobody worried about antenna resonance using a spark transmitter. The transmitter's output circuit was the antenna tuner.
He talked about a quarter-mile long wire antenna along the side of a corn field that was struck during a particularly strong storm. Said the whole quarter-mile of wire was just gone. No trace, except for one scorched piece about twelve feet long.
That antenna was connected to a ground rod when it was not on the air. Seems like it would have done a number to his station if it had been connected.
73