|
lightening - groiund currents
I wrote my warning because I have several times suffered from the effect of lightening strikes at some distance, certainly more than a kilometer. My worst case took out a
computer, modem and router, I now use a correctly instally surge protector.
I also had some years ago when a I used a 4ft disk on the roof on and AZ-EL
computer controlled tracking systenm to track weather satellites. Here distant
lightening strikes induced currents in the coaxial out running from the low noise
giga-hertz amplifier at the centre of the dish to the main receiver in the house, this cable carried rf down and 12v dc up to the amplifier. The currents induced in the outer caused transient spikes on the inner that blew up the fet amplifier in the LNA. I cured this by the
proper use of faraday shields, and voltage regulators. So to say 20 meterrs as a limit for
ground currents of consequence did not apply inb any of these instances.
|