[Hallicrafters] Antenna Lightning Protection

[Carl]

I have never grounded a tower (except with on ground insulated radials 
for a 160M shunt feed at a prior QTH) and havent taken a direct hit in 
over 40 years.

At this QTH there are 4 towers ranging from 60 to 180'. The deepest hole 
before hitting solid ledge is around 2 1/2 ' and the two 100' towers sit 
in concrete. The 60' sits on a Rohn base plate ON the surface. The 
concrete for the 180' is only 9-14" thick and epoxy bonded to the rock 
along with some rebar into 3' deep drilled and epoxyed holes. It sits on 
a pier pin.

Yes, concrete is not an insulator but I havent hooked up a megger to see 
what its resistance is.

All guys are 1/4" EHS broken up with insulators.

All have been up here on top of the highest hill within 21 miles 
for18-20 years.

The only lightning damage has been from strikes on the power poles and 
limited to blown telephones, modems and Faxes. Induced voltage on the 
Beverages has taken out an occassional toroid 9:1 transformer or preamp 
transistor. No trees or buildings within 300+ ' of the big tower have 
been hit.

For the past 5 years my Internet is via a 5.8 gHz link with all the 
electronics at the 120' level; never even a burp.

The big tower has 3 trailers at the base, 2 for storage and one has 
several 2 way commercial radio repeaters and pagers running 24/7. Never 
had one fail from lightning or trailer take a hit.

Back in the early 60's experiments were run in Florida, the lightning 
capital of the USA. The ungrounded structures and equipment received far 
less damage than the grounded ones. The theory is that the ungrounded 
structures build up a charge that repels a direct strike. This is the 
Cone of Silence that I referred to earlier; not the revisionist one in 
current use. Ive heard the corona sizzle many times and then watch the 
actual strike hit well off into the woods.

However any mention of those tests appears to have been surpressed in 
current mention. Companies make the big bucks peddling grounding 
equipment, structures still get hit and insurance companies still make 
payouts.

I figure that I have exceeded the point of pure luck by a wide margin 
and there is truth to the old theory.

During those 40 years I havent lived anywhere that a good ground was 
possible anyway. The soil has been bony, rocky, sand and now pure ledge 
at this location. My AC ground is two 8' rods driven horizontally, I had 
to blast for the house foundation.

"Well that's my story and Im sticking to it" ......stolen from Collin 
Raye.

Carl
KM1H



----- Original Message ----- 
From: "Roger (K8RI)" <Hallicraftersgroup at rogerhalstead.com>
To: "Carl" <km1h at jeremy.mv.com>
Cc: <hallicrafters at mailman.qth.net>
Sent: Thursday, January 08, 2009 1:59 AM
Subject: Re: [Hallicrafters] Antenna Lightning Protection


>
>
> Carl wrote:
>> Interesting Bob.  Ive been arguing about the Cone concept for decades
>> but the established orthodoxy  rebels violently whenever it is
>> mentioned. Ive left several antenna forums in disgust over this.
>>
> I have to agree with you guys.  With the top of my tower ..OK, 
> antennas
> an mast reaching 130' I've seen a LOT of stuff within that cone take
> direct hits. Actually my neighbor and I were standing by the power 
> pole
> with the pig on top (at the end of my driveway with a thunderstorm way
> off in the distance. All of a sudden we bout went deaf when that pole
> took a direct hit. To say we beat a hasty retreat would be an
> understatement.  That is not to say my tower doesn't get hit. As I've
> mentioned before, it has taken an average of 3 verified direct hits a
> year and the las two years were strike free.  OTOH the tower has been
> ignored for power poles, pine trees, houses, ... you name it. One
> multiple strike hit the tower several times, the pole out front, the
> pole and transformer to the north AND a yound pine tree almost a 100
> yards to the East.  The Pine may have been 60 to 70' tall and maybe a
> foot around at the base.  The largest piece left was about 3' long and
> it was found about 40 feet from the base of the tree, stuck into the
> ground over a foot.
>
> Admittedly lightning is unpredictable, but I have my doubts about the
> reliability of the so called "cone of protection.
>
> So far, since finishing the elaborate ground system with 32 or 33 8'
> ground rods, cad welded (TM) to over 600' of bare #2, tied into a 
> single
> point ground I've had no damage even after taking 15 direct hits over
> the years and that is without disconnecting anything. For one it'd too
> difficult to get at the connections.  If I heard a storm coming it'd 
> be
> too late to safely get in there any way. By the time  could get every
> thing disconnected the storm and most dangerous part would be past.
>
> I think one mistake many make it disconnecting cables and not 
> grounding
> them.  Floating coax and ladder line can reach some almost 
> unbelievable
> potentials that can be in the 100's of thousands of volts.  They just
> keep charging until they arc to *something*
>
> 73
>
> Roger (K8RI)
>> Carl
>> KM1H
>>
>>
>>
>>
> ______________________________________________________________
>