I would suspect a poor grounding system on the tower. If the ground is a
rod driven into the Earth, then the impedance needs to be as low as
possible. Once the ground system takes a surge, glass
(( (crystalls?)))
will formin the dirt on and around the rod. The impedance then climbs
and the numberof strikes to the tower increase. The amount of
impedance in your groundnetwork determines the amount of static charge
that can build on the towerand how fast the charge can bleed.

(((The tower sites are only about 100 feet apart, ground substance is
the same, clay/rocks, 1st foot then clay…… The first tower ground, is
a 4 ft hole, with ¾" rebar then driven deeper,1.5ft, w/ horz bars 1ft
on center from bottom of hole to top, where a ¾ steel plate was welded
to vertical bars, and to the plate, strong hinge plate connected to 25
rohn tower. The 'other site', is two 4" pipe, 5ft, in the ground, and
welded to fence. Fence is 2"2/8 upset tubing that goes around
property/everything welded. ((fence is 5 foot tall) and as stated part
of the 'gournding system',,,? The first 'site' was not connected to
the primenter fence,,problem???)) If you are familur with the ''bird
tilting over and drinking from the cup", you can picture in your minds
eye, my 'tilting tower'. It is about 75ft tall, with a uhf/vhf duel
band at top of mast, four ft. below that is a two meter horz omni
ground plane.)))

Can you describe how each tower was configured at the top and how it
was grounded? What is important to know if the top ended up with sharp
point (mast, VHF vertical antenna, etc.) or Yagi type antenna, like
tribander etc. without anything pointy protruding above.
Yuri, K3BU

((( Both towers carried almost the same 'items', vhf/uhf , and 4 ft
below that, clover leaf horz ground plane.)))


but their tower lighting chokes kept
lightning off the a-c power source.

((( What do you call these chokes, I know I have read about, but at
the moment I am blank.)))


The broadcaster starts his lightning protection at the tower top with
a small lightning rod extending above and beyond the beacon to take
the hit and avoid expensive repairs at the tower top.


((( Is this something like the antennas I have seen that have a
'center core' copper rod???)))

Tower guy insulators are doubled and tripled where they connect to the
tower so that static breakdown occurs to the earth instead of at the
tower.


((( Where do I 'see/read' about this??)))


One such line was on a small single story U-Stor-It building between
two very tall radio station towers, that was assumed to be lightning
proof due to it's location. It was hit and hit hard when neither
tower was hit

……"How did your team "know" what was struck?

"""…my question was and is,,,, why?




(((((((((((((((((((This statement is the one that makes the
most sense to me)))))))))))))))

Lightning is Female. 20 million volts & 100 thousand Amps will do as
it damm
well pleases!

((((Last, but not least,,,,,,, thank you, WILL implement input,
cl&73))))

Sorry for the spelling error crystalls should be crystals. When lightning
hits the Earth, the heat it generates is enough to make glass which is an
insulator. The ground rod becomes isolated from the Earth. If you spread
out the contact area with the Earth as with the fence around the perimeter
of the property, then the energy is not concentrated to one spot. The over
all impedance is also much lower. I would install a ring grounding system
around the tower. A 32ft. diameter ring would do nicely in a clay/rocky
soil. Place 8ft. ground rods in the ground every 16 ft along the 32 ft.
diameter circle (approx. 6 rods). Each rod is then connected to the tower
base with a multistrand 00 copper wire and a ring of 00 copper to connect
each rod together. The connections should be cad welded or at least treated
with a deoxit coating to prevent corrosion. I have had excellent luck with
this approach, no lightning hits and my tower sits up at 870ft. ASL or 650
ft. above average terrain. Note: the tower has a strike counter hooked up
to it so I know no hits have happened. Go to this link to read more
http://www.polyphaser.com/ppc_pen_home.asp .

Frank N1SIF

"CIL" wrote in message
...

I would suspect a poor grounding system on the tower. If the ground is a
rod driven into the Earth, then the impedance needs to be as low as
possible. Once the ground system takes a surge, glass
(( (crystalls?)))
will formin the dirt on and around the rod. The impedance then climbs
and the numberof strikes to the tower increase. The amount of
impedance in your groundnetwork determines the amount of static charge
that can build on the towerand how fast the charge can bleed.

(((The tower sites are only about 100 feet apart, ground substance is
the same, clay/rocks, 1st foot then clay.. The first tower ground, is
a 4 ft hole, with ¾" rebar then driven deeper,1.5ft, w/ horz bars 1ft
on center from bottom of hole to top, where a ¾ steel plate was welded
to vertical bars, and to the plate, strong hinge plate connected to 25
rohn tower. The 'other site', is two 4" pipe, 5ft, in the ground, and
welded to fence. Fence is 2"2/8 upset tubing that goes around
property/everything welded. ((fence is 5 foot tall) and as stated part
of the 'gournding system',,,? The first 'site' was not connected to
the primenter fence,,problem???)) If you are familur with the ''bird
tilting over and drinking from the cup", you can picture in your minds
eye, my 'tilting tower'. It is about 75ft tall, with a uhf/vhf duel
band at top of mast, four ft. below that is a two meter horz omni
ground plane.)))

Can you describe how each tower was configured at the top and how it
was grounded? What is important to know if the top ended up with sharp
point (mast, VHF vertical antenna, etc.) or Yagi type antenna, like
tribander etc. without anything pointy protruding above.
Yuri, K3BU

((( Both towers carried almost the same 'items', vhf/uhf , and 4 ft
below that, clover leaf horz ground plane.)))


but their tower lighting chokes kept
lightning off the a-c power source.

((( What do you call these chokes, I know I have read about, but at
the moment I am blank.)))


The broadcaster starts his lightning protection at the tower top with
a small lightning rod extending above and beyond the beacon to take
the hit and avoid expensive repairs at the tower top.


((( Is this something like the antennas I have seen that have a
'center core' copper rod???)))

Tower guy insulators are doubled and tripled where they connect to the
tower so that static breakdown occurs to the earth instead of at the
tower.


((( Where do I 'see/read' about this??)))


One such line was on a small single story U-Stor-It building between
two very tall radio station towers, that was assumed to be lightning
proof due to it's location. It was hit and hit hard when neither
tower was hit

.."How did your team "know" what was struck?

""".my question was and is,,,, why?




(((((((((((((((((((This statement is the one that makes the
most sense to me)))))))))))))))

Lightning is Female. 20 million volts & 100 thousand Amps will do as
it damm
well pleases!

((((Last, but not least,,,,,,, thank you, WILL implement input,
cl&73))))

Grounding a tower does not help prevent it from getting hit by
lightning. It does however help route the charge safely to ground when
hit. A tower may actually be a little less likely to be hit if not
grounded but that is not a good thing to do.

Placing ground rods out in a radius like the spokes of a wheel around
a tower is a good thing. Placing a connecting wire between rods on the
circle is a waste of wire. It would be better to use that additional
wire for additional radials. The current will travel out away from the
tower. Each ground lead going away from the tower will share the
current. There is no significant current difference between the ground
rods so the ring connection does no good.

First a few ground rods should be placed as close to the tower as
possible to have the shortest lead length from the tower. Additional
ground rods placed on the "spokes" going out away from the tower at
distances twice the rod lengths along each spoke.

Having the connecting wires buried going to the other ground rods will
increase the ground system effectiveness also.

Not being struck because you have a good ground system is not proof
that the ground system prevented it.

73
Gary K4FMX


On Tue, 19 Oct 2004 16:15:04 -0400, "leaf"
wrote:

Sorry for the spelling error crystalls should be crystals. When lightning
hits the Earth, the heat it generates is enough to make glass which is an
insulator. The ground rod becomes isolated from the Earth. If you spread
out the contact area with the Earth as with the fence around the perimeter
of the property, then the energy is not concentrated to one spot. The over
all impedance is also much lower. I would install a ring grounding system
around the tower. A 32ft. diameter ring would do nicely in a clay/rocky
soil. Place 8ft. ground rods in the ground every 16 ft along the 32 ft.
diameter circle (approx. 6 rods). Each rod is then connected to the tower
base with a multistrand 00 copper wire and a ring of 00 copper to connect
each rod together. The connections should be cad welded or at least treated
with a deoxit coating to prevent corrosion. I have had excellent luck with
this approach, no lightning hits and my tower sits up at 870ft. ASL or 650
ft. above average terrain. Note: the tower has a strike counter hooked up
to it so I know no hits have happened. Go to this link to read more
http://www.polyphaser.com/ppc_pen_home.asp .

Frank N1SIF

"CIL" wrote in message
.. .

I would suspect a poor grounding system on the tower. If the ground is a
rod driven into the Earth, then the impedance needs to be as low as
possible. Once the ground system takes a surge, glass
(( (crystalls?)))
will formin the dirt on and around the rod. The impedance then climbs
and the numberof strikes to the tower increase. The amount of
impedance in your groundnetwork determines the amount of static charge
that can build on the towerand how fast the charge can bleed.

(((The tower sites are only about 100 feet apart, ground substance is
the same, clay/rocks, 1st foot then clay.. The first tower ground, is
a 4 ft hole, with ¾" rebar then driven deeper,1.5ft, w/ horz bars 1ft
on center from bottom of hole to top, where a ¾ steel plate was welded
to vertical bars, and to the plate, strong hinge plate connected to 25
rohn tower. The 'other site', is two 4" pipe, 5ft, in the ground, and
welded to fence. Fence is 2"2/8 upset tubing that goes around
property/everything welded. ((fence is 5 foot tall) and as stated part
of the 'gournding system',,,? The first 'site' was not connected to
the primenter fence,,problem???)) If you are familur with the ''bird
tilting over and drinking from the cup", you can picture in your minds
eye, my 'tilting tower'. It is about 75ft tall, with a uhf/vhf duel
band at top of mast, four ft. below that is a two meter horz omni
ground plane.)))

Can you describe how each tower was configured at the top and how it
was grounded? What is important to know if the top ended up with sharp
point (mast, VHF vertical antenna, etc.) or Yagi type antenna, like
tribander etc. without anything pointy protruding above.
Yuri, K3BU

((( Both towers carried almost the same 'items', vhf/uhf , and 4 ft
below that, clover leaf horz ground plane.)))


but their tower lighting chokes kept
lightning off the a-c power source.

((( What do you call these chokes, I know I have read about, but at
the moment I am blank.)))


The broadcaster starts his lightning protection at the tower top with
a small lightning rod extending above and beyond the beacon to take
the hit and avoid expensive repairs at the tower top.


((( Is this something like the antennas I have seen that have a
'center core' copper rod???)))

Tower guy insulators are doubled and tripled where they connect to the
tower so that static breakdown occurs to the earth instead of at the
tower.


((( Where do I 'see/read' about this??)))


One such line was on a small single story U-Stor-It building between
two very tall radio station towers, that was assumed to be lightning
proof due to it's location. It was hit and hit hard when neither
tower was hit

.."How did your team "know" what was struck?

""".my question was and is,,,, why?




(((((((((((((((((((This statement is the one that makes the
most sense to me)))))))))))))))

Lightning is Female. 20 million volts & 100 thousand Amps will do as
it damm
well pleases!

((((Last, but not least,,,,,,, thank you, WILL implement input,
cl&73))))

"CIL" wrote in message
...
but their tower lighting chokes kept
lightning off the a-c power source.

((( What do you call these chokes, I know I have read about, but at
the moment I am blank.)))


Perhaps you are thinking of an Austin Ring transformer to couple the
power to the beacon lights...........

CIL wrote:
"What do you call these chokes?"

Tower lighting chokes. Every a-c power wire on most AM broadcast towers
is fed through through a high-current r-f choke, beacon, side lights,
and neutral. It avoids shorting out the tower at its base for the r-f
signal.

Another device is used at some stations for the same purpose. It is
called an Austin transformer and consists linked loops to transfer a-c
power while providing little r-f coupling.

Tower lighting chokes must provide better performance for the price
because they seem more prevalent. Tower lighting chokes may all be
wraped around one form or on separate forms. They not only provide good
r-f isolation, but they provide almost complete lightning isolation.
They really keep lightning out of the a-c power circuits on the ground
when used with appropriate bypass capacitors and arresters.

Best regards, Richard Harrison, KB5WZI

These guys http://www.harger.com/ are the big boys in the lightning
protection business... Get this http://www.harger.com/equipcat.htm it will
answer alot of questions.
Also, see www.polyphaser.com
I have towers at work that the tower crews say the air terminal is kept
shiny from so many hits.


N2QEW