Am 05.07.19 um 23:26 schrieb Poul-Henning Kamp:
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In message <28f942e8-b61d-4fa5-929d-923184828...@n1k.org>, Bob kb8tq writes:
Energy flow is indeed inside the cable if things are set up and operating
correctly.
Please note in this context that *nothing* about lightning strikes
works the way you would assume it does.
A friend of mine got his ham radio station pulverized by a lightning
hit in the garden. He had written his PHD thesis on the breakdown
mechanism when charge powers its way through gases.
I call that an a posteriori field research addendum. ;-)
Cables run inside steel tubes protect the steel tube from lightning
current because copper is a better conductor than steel - in
particular when the leading flank is measured in kV/uS and the
current in kA.
Likewise, a 90 degree bend or a loop on the cable is a huge
inductance to get all that high frequency energy through, so
lightning tend to jump from bends and loops, to less inductive
paths if possible
Be careful with EMI/EMC clam-on ferrites, they can explode in
lightning strikes.
Then I look upon my pole as a 2 meter long clamp-on ferrite.
That 7 mm Aircell cable won't conduct much better than the pole,
and the outside of the pole will look quite, eh, attractive, given that
king size common mode choke.
And then, at the 90° cable corner to my lab, the lightning bolt may
continue
downwards through earth on its highway to hell..
cheers, Gerhard
(Unix V6 on 1 of the 5 PDP 11/40E that ever existed)
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