[Antennas] Dumb question?

[Eric Lemmon]

Ron,

You have re-kindled a very hot topic.  Although there are many sensational
claims for "dissipation arrays" and "static absorbers", most insurance
underwriters and the National Fire Protection Association- which is the
author of NFPA 780, the Lightning Protection Code, do not recognize such
devices as suitable for lightning protection.

Just as there are passionate claims of alien abduction and Roswell landings,
there are apocryphal claims of the utility of dissipation arrays, but there
is absolutely NO credible evidence that they work.  Most insurers will deny
claims for lightning damage if the structure or equipment was not protected
with a system that is recognized in NFPA 780.  Do not be swayed by tabloid
articles; stick with the facts.  There is some very good instruction on
tower lightning protection and grounding in NFPA 70, the National Electrical
Code.  Your County Electrical Inspector can advise you on the relevant
articles.

73, Eric Lemmon WB6FLY
 

-----Original Message-----
From: antennas-bounces at mailman.qth.net
[mailto:antennas-bounces at mailman.qth.net] On Behalf Of bonddaleena at aol.com
Sent: Sunday, May 17, 2009 1:01 PM
To: antennas at mailman.qth.net
Subject: [Antennas] Dumb question?

Hi, here is a question I would like to put before the list....

I have just finished getting my 2 - 95 foot towers up. They are well 
engineered and guyed VERY well with 1/4" EHS guy wire.
The towers are well grounded with low imped copper strap from each leg 
to a system of 8' ground rods all interconnected.
I have had tall towers like this at my last 4 QTHs and never had a 
problem with lightning DIRECTLY hitting a tower. I have had some 'near 
misses' which have taken out several mast mounted VHF and UHF GaaSFET 
preamps , until I learned how to protect them.

However, I was watching a special last night on Ben Franklin and they 
went into great detail about how he invented the 'lightning rod' 
concept.
I have read extensively about this subject, but still have this 
question on my shrinking mind:

Since I leave near the thunderstorm capitol of the USA (Florida), would 
I gain any safety by installing a very pointed conductor at the very 
top of my tower's mast?

One tower will have a pair of 432 MHz long yagis at 115'. They will be 
fed with 7/8" CATV hardline and have the preamp near the rotor.
I have ground straps to bypass the rotor. The antennas are all at DC 
ground, so there would be a direct path to ground for everything on the 
tower.

My feeling is that by placing a sharply pointed 'tip' to the top of the 
mast will help dissipate a charge before it builds to strike potential. 
As you are aware, this is how Ben's stuff works. Lightning rods cannot 
withstand a direct 'hit'. They are for dissipation purposes.

OR, am I inviting a strike with the pointy rod????

I've not seen this topic discussed before.

Thank you in advance.

ron
N4UE
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