Posted by
Jim Brown-10 on
Nov 07, 2017; 5:49pm
URL: http://elecraft.85.s1.nabble.com/Lightening-damage-tp7635695p7635737.html
On 11/7/2017 9:31 AM, Gmail - George wrote:
> Any electronics at the top that is connected at the bottom
> can have that potential on the equipment case (a DC ground loop so to
> speak) of 100 volts. Most times it is much higher.
It is a serious mistake to view lightning as DC. While there MAY be a DC
component, lightning is primarily an RF event. IEEE studies show that
the energy in lightning is (very) broadly centered around 1 MHz. As far
as lightning (and any other RF) is concerned, that tower is an antenna,
and must be understood as an antenna.
It is also a serious mistake to think of our antennas as the only means
by which lightning enters our homes. Lightning comes in on power wiring,
telephone wiring, and CATV wiring. It also induces current on wiring
within our homes.
It is VERY common for lightning currents induced on wired Ethernet
cables, connected to equipment with shunt mode surge protectors (MOVs)
to fry computers (especially their Ethernet circuitry) in the loop that
includes their green wires back to the panel. This happens in homes and
offices with no radio antennas at all.
All of this is why the most important element of lightning protection,
BY FAR, is proper bonding of all equipment and grounds in a building.
This is all covered in considerable detail in N0AX's new ARRL book on
Grounding and Bonding for hams. It is of FAR greater value than all the
surge protectors you could possibly buy. And you can get most of the
same information for free from these slides.
http://k9yc.com/GroundingAndAudio.pdf73, Jim K9YC
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