Disconnecting, grounding, lightning, etc..

[Jay Schwisow]

Here is an eham posting from a friend and RF engineer with Sprint - Mike
Higgins K6AER. Mike has helped me with my station and taught classes to
many. There is lots more to protecting your house, family and belongings
than just disconnecting coax...read on.

 From Mike Higgins on Eham 3/2006:

Well it is that time of the year when postings turn to grounding and
lighting protection.

So much information has been posted on lightning protection in this
fourm you could spend hours going through all the information listed and
I would recommend doing so. Use the search engine in eHam and by all
means forget the naysayers of grounding. Go to the PolyPhaser site and
read their tutorials on lightning protection. Go to Lyncole, Hagar and
ICE (Industrial Communications Engineers) and read their tutorials on
grounding. There is no short cut to lighting protection. Your whole
station and home needs to be addressed as a complete solution. Now if
you live in the Northwest you can skip the rest of this article for your
chances are very slim you would even see a thunderstorm. For the rest of
the county this is an aspect of the hobby we have to deal with. This
article is a reader's digest version of what must be done for surge
protection and I hope it start you thinking about your home and station.

Every other year on average my station gets hit by lightning. This was
not a problem when I lived in LA; I had a greater chance of being hit by
stray bullets. I live in a very high lightning prone area called the
Palmer divide in Colorado. June through August we have thunder storms
every day with up to 40,000 strikes a day on average during those
months. I am on my 3rd GP-9 antenna at the top of the tower. When a
storm has gone by and I find what's left of a GP-9 in toasted shards all
over the ranch, it doesn't take a rocket scientist to know what
happened. I have lost no base station equipment to a lightning strikes
but I have spent considerable time putting in proper grounding and surge
protection on my station. As for the tower top fiberglass omni sticks,
they're sacrificial and that just the cost of doing business where I live.

Proper grounding and surge protection works and works very well. The key
is setting up low resistance grounding and the proper installation of
grounding material. Disconnecting you equipment and putting it into a
Faraday Shield box will work well but if you live in an area like my QTH
you would be off the air for 3-4 months every year. Some hams like my
self have more than one radio and going this route would mean my hobby
is station assembly. I can't speak for most hams but after doing that a
few times it looses its novelty.

The cell phone industry looses less then 20 sites a year to lightning.
There are approximately 500,000 sites between Verizon, Nextel, Cingular,
Sprint and others. Generally it is because the DSL line is struck and
not the radio equipment. In the cell phone industry we ground at the top
of the tower, base of the tower and where the cable goes into the
facility. The facility has a ground halo inside and the all equipment is
grounded to NEC code. Surge protectors are connected for all incoming
and outgoing lines at the ground demarcation point. Site ground
resistance is generally below 3 ohms. Four 20 foot deep ground rods is a
grounding minimum. The AC entry panel has surge protectors (95% of all
lightning damage comes in through the AC panel) and most importantly all
the facility grounding is bonded together.

Power lines take by far the greatest hits and the pole flash-over-rods
pass any surges below 10,000 volts. That still leaves a lot voltage
coming down the power line. The primary and secondary portion of the
pole transformer can arc over and your home is next in line. Your home
AC panel should have a surge protectors connected to the panel. You
worry about your ham equipment but what about your expensive
entertainment and appliances not to mention the possibility of fire. You
can protect your home and panel for under $100. Intermatic makes the
Panel Gard model number IG1240RC surge protector for $60 not including
the two additional circuit breakers. This unit has LED's to indicate the
units status and wither you have taken a power surge. Installation is
just three wires into the panel.

Did I mention lightning rods for the roof? Lightning is fickle and might
miss your gorgeous tower and strike through the roof to the electrical
wiring in the ceiling. The ground return in your home wiring connects to
the master ground in your AC panel. Remember a lighting discharge is
looking for the lowest impedance path to ground, i.e. earth. If your
live in a highly lightning prone areas like Colorado, Florida and much
of the mid west, lighting rods are a good investment. National Lightning
Protection in Denver makes all the necessary material to install your
lightning rod system. Their web site is a wealth of information.

In my own station, all grounding is bonded with a number “0” solid
copper bonding wire. My ground resistance is less than 3 ohms. I have
several deep (20ft. by 2 inch) ground rods for the tower, AC panel and
shack location. I also have a surface ground field of 21 8ft. ground
rods spaced 16 feet apart, spread out in radials from the tower. At the
base of the tower is a lightning/surge protection panel for the coax,
rotor cables and stepper motors on the beam. For the surge protection
box I use 2 inch wide copper strap. Copper strap has much lower
impedance than copper wire and much of lightning's energy is in the RF
spectrum.

Coaxes are grounded at the top of the tower as well as the base. The AC
panel has a commercial lightning protection panel to take care of
incoming AC surges. The whole station is run on a pair of 3000 watt APC
UPS systems to isolate the AC main from the equipment for minor surges.
At the station, coaxes are terminated at a pair of grounded Alpha Delta
coax switches and during storms the coax switches are in the grounded
COM position. All equipment is grounded to a master ground buss bar on
the back of the operating station. The master AC feed to the station has
a commercial disconnect in the shack. I know many of you will this is
excessive but proof is in the pudding. I have suffered no equipment
losses due to lightning strikes.

Remember if the cell phone, radio, public service and computer industry
disconnected equipment for every summer storm, you would not have
communications coverage or internet service for five months every year.
The communication industry is connected 24/7. As a result, proper
lightning/surge protection with good grounding works. Is it 100 % full
proof…NO, but it is infinitely more effective than sticking you head in
the sand with denial. You don't plan on getting into an accident but you
have car insurance. Lightning surge protection is an insurance policy
and another tool in your station/home safety plan.

Many hams have their station and personal electronics insured but
collecting and replacing equipment is tedious and would it not be easier
to prevent the damage in the first place. Due the proper diligence and
you'll sleep better at night.


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[Charly]

Jay... what a wonderful system for grounding you have made ! and your
"ground resistance is less than 3 ohms"... great.   When I disconnect my
antennas, My ground resistance is zero ohms or infinity, which ever is
correct way to say it.

Most "ground it" guys get off on the vast trouble it takes to disconnect
things.  Why not work on that aspect rather than getting embroilled in
expensive commercial standards grounding?  In Fla, I had 8 coaxes coming in,
2 rotor, and one remote sw.outside.  With remote switches on the window
patch panel, I had to unplug one coax, 2 rotor and one remote plug*.  Four
plugs take maybe 30 seconds to un-do.   Switching off my master bench AC
took another 5 seconds.  In bad storms coming, I also unplugged the master
AC from the wall and the shack master RF ground line... taking another 15
seconds.   Is 50 seconds too much time?

*a little more work coudda put the rotors and remote onto one big Jones
plug, reducing the plug number to TWO.  Then, I would have been down to
about 30 seconds for complete disconnect.

73

Charles Harpole
[hidden email]

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