[TowerTalk] bleed-off lightning devices

[Lee Buller]

At 10:54 PM 8/5/97 -0600, you wrote:
K0WA responds to the following as well....read on.....

>(N4KG   response  to W 5 H V V  below)
>
>On Tue, 5 Aug 1997 20:48:34 -0500 w5hvv@aeneas.net (Roderick M.
>Fitz-Randolph) writes:
>
>>My first lightning hit here (I've had 3 in 3 years) was off a tip
>>end of the driven element on my 40-2CD at 140'.  It turned the trap
>>on that side of the driven element into a real crispy critter.  When
>>I reinstalled it (wadda pain) after replacement of the trap and coax,
>>I also installed a 10 foot high galvanized tube above the mast that
>>held my antennas.  This tube has 5 each 18" long (very sharp ended)
>>spikes brazed to the top of the tube - one straight up and the rest
>>at 45 degrees to the vertical and in the four directions.
>>
>>I've been hit twice since then but the lightning has hit my "pointy,
>>spikey thing" and not my antennas.... for which I am most thankful.
>>
>>There is no telling if the sharp spikes at the top have bled off 
>>enough
>>charge to prevent any more hits or not.  But it sure has caught the
>>2nd and 3rd hits and saved me a bunch of money in that I haven't had
>>to take down the TH7DX and 40-2CD from off the top of the 130' tower
>>to replace any more traps!!  For that I am thankful and I am glad I
>>put the "charge bleeder/lightning attracter" up there.  I don't think
>>I'll ever have another tower in my lifetime without one up there, way
>>above all the antennas.
>>
>>Rod, W5HVV
>>
>>

Here is Kansas it is flat and we do get our share of great thunderstorms.
It seems everything gets struck here...from golfers on the fairway to large
towers.  Lightening is rather indescriminate here in Kansas.

Harvey County is really flat....flatter than western Kansas.  The Newton
Amatuer Radio Club has a repeater on the local flour mill.  The antenna was
a DB products phased array on a 20 foot aluminum pole.  The pole was
grounded to the mill's conduit system.  OK, I know, it is not the best
ground, but it was the only ground!

The antenna took a beating and so did the hard line coax from lightening
strikes.  The repeater was off the air more than it was on the air.  The
mill is 300 foot high over the terrain...we can see up to 30 miles away
easily.  The antenna finally quit working so we removed it from the
mill...not an easy task...and started to repair it.  The thing was a mess
and could not be repaired.  The phasing harness was inside the pole.  (It
was a real old antenna)

So we stripped off the elements and used the pole to mount a Cushcraft phase
dipole array.  We had to extend the pole to 25 feet to get it to fit, but
the antenna was great.  Flat at 146.61.  Good match.  We also put in CATV
hardline with impedence transformers at both ends.  

The pole, stick 25 feet higher than the mill, received multiple hits which
toasted the phasing harness, one dipole array and blew a hole the size of a
dime in the top impedence transformer.  Kaboom.  Did not hurt the repeater
as the lighting strike went through the transformer to ground (the conduit
electrical panel).

We took the antenna down again and repaired the antenna and the phasing
harness.  But, we took a four foot SS metal rod and place a point on it that
could kill an elephant!  Very sharp.  We mounted the rod at the top of the
pole with SS hose clamps, bonded #4 copper wired to the rod and brought it
down the pole and bonded it to the conduit ground.  That was all we had for
a ground.

Since we did that over two years ago, we have had not one lightening hit.
Not one!  The repeater has been on the air all that time...even during RACES
activations and horrible lightenings storms.  Kept on kerchunking away all
night.

Again, the concept was to bleed off any charge.  From practical
experiemce...it seems to work.

Lee Buller
k0wa@southwind.net


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