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Re: Lightening and mast mounted preamps



Hello Jon (and others)

<<The thread of lightning protection comes up quite a bit on the Towertalk
reflector (towertalk@contesting.com).  There's a LOT that many hams do not
do.

First off, the idea of disconnecting coax from rigs is subject to debate.
Lightning will find the shortest path to earth (note, I did not say
"ground") and sometimes that could literally be an arc through the air to
some other piece of equipment.  That can happen when you disconnect.
<<

In my experience over a few decades and with the current installation thats 
pretty accurate.  In Houston we have a 51 foot tower with a 20 foot 2.5 inch 
"heavy" steel mast that is 15 feet higher then the tower (5 feet is 
nested)...there is an HF beam, right angles to it is a 6 meter beam and some 
distance higher then that are some verticals for VHF...and a copper rod 
which is the highest point of all has a direct connect to the rods on the 
legs of the tower withheavy copper wiring.  Around the house there are some 
LEO arrays, a developing BUD for AO-40, and some DirecTV dishes all are 
connected with 02 wiring and AL flashing to grounds and each other.

In the ground are 100 8 foot copper rods connected with 02 wiring (a lot of 
pounding) and the front and back yard is overlaid with chickenwire and 
underneath that are some wiring runs (we completly redid the yard upon 
moving in). Each leg of the tower goes to 6 (two per leg) 16 foot copper 
rods which are all connected to each other (had the posthole digger...in the 
10X10X10 hole for the tower we have 16 foot "piles" driven down to 26 
feet..that tower isnt going anywhere (we get Hurricanes here).  EAch room in 
the house has a direct run to ground for the AC and everything is bonded 
together.

August 20,2002 had some really serious storms moving through the area.  I 
had left the tower up overriding the computer control to crank it down 
because I wanted to "watch" the storms going through Houston but not so much 
through our area.  Roo and I were sitting down to dinner when the sky in the 
skylight at the table started going really green and the wind started 
shifting.

We are both pilots and Roo looked at me and said "should we lower the tower" 
and then "bang".  We both could see the flash and smell the ozone (the cats 
ran and hid).

The lights never dimmed or even faltered.  Not one of the preamps were 
damaged, not one of the radios...nothing except the copper rod that stood up 
above all the other antennas on the tower was shorter by about 6 inches.

Its the lesson I learned in the TV broadcast business long ago (when I was a 
consultant) ground everything and make the "ground" really earth.  Then 
everything is fine.

Robert Oler WB5MZO

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