[Boatanchors] new Ground system

[Glen Zook]

I am a firm believer in the use of dissipation devices
to help "bleed off" the charge in addition to proper
grounding.  There are some "grounding experts" that
rely completely on dissipation devices to "prevent" a
strike (up to over 99.9% effective if properly
installed, but definitely not 100%!) and there are
those who say that dissipation devices are "bunk" and
that you have to "ground the heck" out of everything. 
I believe in installing dissipation devices and then
grounding the "heck" out of everything just in case
you take a strike!

Everything must be grounded.  Each tower leg needs a
separate ground.  Coax shields should be grounded at
the top and bottom of the tower and then again where
they enter the building (if over 10 feet from the
tower and it doesn't hurt to ground them there
anyway!).

There must not be any reversal of direction in the
ground lead.  There must not be any sharp bends
(because of this I recommend stranded wire and not
solid wire because solid wire takes on a permanent
bend if "stepped on", etc., whereas stranded wire will
normally return to its original shape).  Good grounds
are not "pretty"!  Right angle bends are a complete
"no no"!  The list goes on!

I worked for Texas Utilities (now TXU on the stock
exchange) for over 10 years until they eliminated the
telecommunications department in May of 1999.  Around
1994, the microwave tower in Athens, Texas, took 3
direct strikes in a 6 week period.  Since the company
"self insures" for losses up to $1,000,000 they had to
"bear" the costs of the damage.  One strike cost about
$20,000, another $40,000, and the third over $60,000. 
The superintendent over the area in which the tower
was located finally asked for help.

The tower is only 80 feet tall, but sits on a very
high hill just above the service center.  I suggested
putting "spline balls" on the tower.  The regional
technician climbed the tower and installed the spline
balls (of course after they were ordered and
delivered).  About 3 months later, the superintendent
called me and said that they had "taken another
strike".  I asked him how much damage and he replied
"about a dollar".  Two telephone line protectors were
"blown".  I told him that the strike did not come on
the tower but from the telephone line.

>From the day of installation until the present, that
tower has not taken a strike.  Because of this, the
company agreed to install dissipation devices on all
of the microwave and two-way towers that were owned by
the company (of course, towers on which we were just
"renting" space were not included).  The company
averaged about 5 lightning strikes a year that
resulted in damages over $10,000 (even more strikes
that resulted in less damages), especially on the 300
to 500 foot two-way towers in west Texas.  Since the
dissipation devices were installed, not a single tower
has been hit.  At one time, the company had over 300
two-way radio base station licenses and about 100
microwave sites.  However, only about 100 of the base
stations actually had antennas over 50 feet in height.

Then, all of the computer data centers (which a couple
had been hit by lightning over the years) were
equipped with dissipation devices.  None of them have
been hit since.

The use of dissipation devices is not 100% "fool
proof".  You can always build up enough energy to get
a "feeler" started if there is enough intensity in the
area.  But, usually the dissipation devices develop a
"corona" which is fine, because when a "corona" is
present a "feeler" will not start.

For those reading this who are not familar with
lightning strikes, they do not start from the sky. 
Instead, a "feeler" starts from the grounded object
and as it works its way upward, the actual strike then
comes from the sky.  But, if a "feeler" doesn't form,
there will not be a strike.

I didn't use to believe the "feeler" theory.  However,
during my junior year at Georgia Tech (1965) I worked
for the Motorola Service Station which was located
four blocks from the edge of campus.  One day I was
working on a base station that was located outside on
the top of one of the major buildings in downtown
Atlanta.  Now, that was in the days when you didn't
have a "little" service monitor that did everything. 
You had a signal generator weighing in at about 40
pounds, a frequency standard at about 60 pounds, a
modulation monitor at about 10 pounds, a wattmeter,
your tool box (another 30 or 40 pounds), a tube caddy
at around 30 pounds, a "test set" at about 15 pounds,
etc.

Anyway, I was "working away" on the particular base
station (it was in a "outdoor" cabinet) and hadn't
noticed that some "storm clouds" had moved into the
area.  Then, I heard a "crackling" sound and looked
up.  Around the parapet of the building were lightning
rods every 10 feet or so.  From each rod there was a
"feeler" from 8 to over 30 feet long!  Frankly I set a
new world's record on closing up the base station and
getting all of my test equipment, tools, etc. off of
that roof.  I think it was in the neighborhood of 9
nano-seconds!

>From that day onward, I definitely believed that
lightning starts from the ground up.  As I drove away
from the building, there were multiple lightning
strikes.

As I said before, there are different methods of
accomplishing the same thing where lightning
protection is involved.  Each "expert" has his/her own
"pet theories" based on their own experiences.  No one
method is "THE" only way things can be done.  However,
grounding is NOT a science, but is a "black art"!  If
you don't make your sacrifices to the radio/grounding
gods on Halloween, your next year will not be good!

Glen, K9STH


--- Glenn Little <glittle@awod.com> wrote:
 
It is amazing how much money a company will spend in
replacing blown up equipment and still not follow
suggestions for proper grounding.  My references come
from experience, the Motorola R-56 manual and MIL-HDBK 419.

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