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Before:

Believe it or not, this is an antenna matching network (tower shunt feed) for an operating AM broadcast station running 2500W. What do you think might happen here?

The metal shelf bracket will break

The insulator connected to the turnbuckle will arc and set the wood on fire

The plastic toolbox will fill with water and short out the works

It looks great to me; it should last forever

Answer: There really isn't a right answer this time, at least I don't know what it is. My best guess is that somehow RF started to go to ground through the wood (insulator arc or toolbox angle bracket hot with RF), then a carbon trail formed on the wood, arcing and starting the fire. This installation was so silly looking I just had to take pictures of it. I went back a week later the saw the charred results. I don't know how long it actually lasted, but the station was still on the air when I took the pictures! It has since been replaced with a better arrangement where the matching components are inside the building.

After: