[TowerTalk] Lightning Protection

[Nick N3NR]

A good reference on the subject relative to commercial systems is the 
Motorola R56 manual. It's slightly dated, but still a good reference. I have 
seen this manual called out frequently as a reference, or sometimes even a 
requirement, for commercial systems.

You can find a copy here: 
http://www.radioandtrunking.com/downloads/motorola/R56_2005_manual.pdf

Lots of examples and ideas.

73 de Nick N3NR
----- Original Message ----- 
From: "K8RI" <K8RI-on-TowerTalk at tm.net>
To: <towertalk at contesting.com>
Sent: Friday, July 05, 2013 11:46 PM
Subject: Re: [TowerTalk] Lightning Protection


> On 7/5/2013 3:44 PM, Pete Smith N4ZR wrote:
>> Every time Towertalk starts off on one of these threads I feel compelled
>> to add one skeptic's viewpoint, and this time I'm actually going to do 
>> it.
>
> I'm not a EE but I managed to get over in while earning a degree in CS.
>
> I have a 100' 45G that had a 30' mast with a TH5 at 100', a 7L C3i 6-meter 
> Yagi at 115' and a cross boom at 130 feet with a pair of 11L 440s ans a 
> pair of 12L 144 antennas.
> http://www.rogerhalstead.com/ham_files/Tower29.htm
> When first installed this system took  at least 3 direct hits a year for a 
> total of 17 visually verified hits the first 6 years it was up. The only 
> loss was one Polyphaser at the entrance.
> There is over 600 feet of bare #2 CadWelded to 32 or 33 8' ground rods. 
> There are two parallel runs from the tower to the grounding panel and 
> ground rods at the entrance.
> http://www.rogerhalstead.com/ham_files/cablebox.htm  The photo at the 
> entrance is out of date as that panel/box has been replaced with a larger 
> one.
>
> During that time the rigs remained connected to the antennas, power, 
> computers and network.  They stayed connected because the connections were 
> very difficult to access.  I was more concerned about the connections to 
> the computers and network as they are on a different circuit along with 
> the cable connection.
>
> BTW the stations in the house and shop are on serrate electrical feeds 
> although from the same transformer,
>
>> Unless you are an electrical engineer with deep understanding of
>> lightning protection, I think that attempts to replicate a commercial
>> 24/7 always-connected solution are far more likely to fail than to
>> succeed.
>
> Lightening protection is pretty well standardized and there is plenty of 
> information available.  There is no 100% guaranteed, fail safe protection 
> even for the 24 X 7 stations, but they are well protected from most 
> strikes.  It's just that there is no guaranteed protection from the so 
> called, "super strikes" that can be many times more powerful than your run 
> of the mill, every day strikes.
>
> So, yes, the best protection is to disconnect everything from everything 
> else, not just the antennas and power.  Remember a strike a mile away can 
> induce as much as a 1000 volts per meter into a piece of wire,
>
> Another danger is precipitation static,  What heavy snow in high wind can 
> induce into an ungrounded quarter wave, 40 meter vertical is something to 
> behold and I've never seen an ignition coil produce that kind of voltage.
>
> Twas about 35 years ago.  We were in the process of building a house on 
> the NW corner of the family farm.  I had a 40 meter, 1/4 wave vertical 
> about a 100 feet out.  The rig, a Kenwood TS820, was disconnected.  A very 
> strong wind was blowing with heavy snow.  I kept hearing a loud snap or 
> pop!  I looked behind the rig and was surprised to see a FAT blue ARC 
> across the PL259.  The thing is, it wasn't just cross the end but rather 
> arched out a good inch away from the end of the connector, forming a loop 
> that appeared to be close to a couple of inches long and it was loud!. 
> Rain with strong wind can also produce similar results.
>
> I've seen similar results from nearby lightening strikes from the feedline 
> to the 75 meter dipole.
>
>
> <snip>
>
> 73
>
> Roger (K8RI)
>
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