[TowerTalk] commercial towers and lightning

[Jim Jarvis]

W6wrt asked about having something ABOVE our yagi,
to take the brunt of a strike.

On every tower I've seen which was over 190' and therefore
required lighting, there has been a lightning rod, to carry
the strike current.  This saves a lot of light bulbs, and 
climbing.

When a series fed AM tower is struck, there is a lightning gap
at the bottom, which arcs over.  When that arc is lit, it presents
a short circuit to the transmitter, usually resulting in a vswr
tripped shutdown.  

As for FM and commercial antennas on a stick, typically lightning
rods are placed above them, to provide the same sacrificial role
that those associated with tower lighting do.  I usually have a two
meter vertical on the top of my personal towers.  It's sometimes used
for local repeaters.  But I've never been hit directly, so don't know
how effective it would be for lightning protection.

That help?  

n2ea 

Jim Jarvis, President
The Morse Group, LLC
www.themorsegroup.net
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