Thanks Richard, I remember your explanation about a dipole being no
attractor of anything except it's resonant freq. But I guess the the
currents in the coax weren't "near enough equal" in this one case. Kind of
defines lightning as it's own anomoly when it wants to be, huh.

Jack

Richard Harrison wrote
Inside the coax, currents in one conductor induce opposing and near
equal currents in each other, cancelling.

On Mon, 26 Jan 2004 14:14:21 -0500, "Jack Painter"
wrote:

But I guess the the
currents in the coax weren't "near enough equal" in this one case.

This is the definition of Common Mode.

Kind of
defines lightning as it's own anomoly when it wants to be, huh.

It means you lacked the Common Mode protection. Your earlier posting
of:

The coax in question was disconnected about 150' from the house, but
lightning apparently jumped from the tower feed across a foot of air space
and back into the PVC pipe channel housing several coax, which led to the
house. The Drake was the luckiest of the second-story ungrounded shack gear.

screams this big time. There was nothing anomalous about that
lightning strike, it did what it was enabled to do.

73's
Richard Clark, KB7QHC

"Richard Clark" wrote

It means you lacked the Common Mode protection. Your earlier posting
of:

The coax in question was disconnected about 150' from the house, but
lightning apparently jumped from the tower feed across a foot of air
space
and back into the PVC pipe channel housing several coax, which led to
the
house. The Drake was the luckiest of the second-story ungrounded shack
gear.

screams this big time. There was nothing anomalous about that
lightning strike, it did what it was enabled to do.

Richard, do you mean that if the coax had been left connected to the dipole
it would have afforded common-mode protection? I think I understand what
you're saying but would appreciate you tying that principle together.
Thanks.

Jack

On Mon, 26 Jan 2004 16:02:38 -0500, "Jack Painter"
wrote:


Richard, do you mean that if the coax had been left connected to the dipole
it would have afforded common-mode protection? I think I understand what
you're saying but would appreciate you tying that principle together.
Thanks.

Jack

Hi Jack,

Ask yourself "Where is ground in this picture?"

THAT is the Common of the Common Mode. I see it discussed nowhere in
your description. There is the inference of it being back in the
house (code requires it) where lightning eventually found it, the hard
way.

As you describe it:
The coax in question was disconnected about 150' from the house,
disconnected where, how? Up the tower? At the bottom of the tower?
Is the tower grounded? Does the tower ground meet code in being tied
to the house ground? Is the coax grounded? Where? Does it supply
ground? Where?

The Drake was the luckiest of the second-story ungrounded shack gear.
No ground? There are two problems with this statement.
1.) It is unlikely due to code;
2.) It means you accept Common Mode problems.

It being unlikely does not mean you are protected (experience proves
this), it means you went with the flow - of several KV.

73's
Richard Clark, KB7QHC

Richard, my earlier posts described the grounding my friend, here is quick
summary:

1.Well grounded 100' tower, hundreds of feet of many radials, rods, etc.
Survived many strikes.
2. Feedline from tower's dipole was disconnected about 20' from tower where
it enters a buried pvc conduit that travels 150' to house, then up to second
story shack. Where nothing is grounded, except by virtue of house AC
wiring - a bad I know (not mine either).
3. Ground current from the tower strike most likely entered the coax
feedlines at the disconnect point as they entered the pvc conduit then
traveled on into house.
4. House current also took huge jolts, zorching all kinds of connected
equipment, phones, tv's etc.
5. Outbuilding with radio equipment connected took huge hit, ball lightning
inside room fried test cords connected to nothing, hanging on test bench,
where the leads touched tile floor, huge blow-out of tile. AC power blew
wall warts across room, computers next to each other had .22 rifle bullet
sized hole between them. Equipment in this bldg was grounded, and some that
was was damaged, others not touched. In short, a massive, multiple
strike-path hit that may not be protectable from - but I realize there was a
lot missing from a good ground picture here also.

Jack

"Richard Clark" wrote
Ask yourself "Where is ground in this picture?"

THAT is the Common of the Common Mode. I see it discussed nowhere in
your description. There is the inference of it being back in the
house (code requires it) where lightning eventually found it, the hard
way.

As you describe it:
The coax in question was disconnected about 150' from the house,
disconnected where, how? Up the tower? At the bottom of the tower?
Is the tower grounded? Does the tower ground meet code in being tied
to the house ground? Is the coax grounded? Where? Does it supply
ground? Where?

The Drake was the luckiest of the second-story ungrounded shack gear.
No ground? There are two problems with this statement.
1.) It is unlikely due to code;
2.) It means you accept Common Mode problems.

It being unlikely does not mean you are protected (experience proves
this), it means you went with the flow - of several KV.

73's
Richard Clark, KB7QHC

On Mon, 26 Jan 2004 21:07:24 -0500, "Jack Painter"
wrote:

Richard, my earlier posts described the grounding my friend, here is quick
summary:

1.Well grounded 100' tower, hundreds of feet of many radials, rods, etc.
Survived many strikes.
2. Feedline from tower's dipole was disconnected about 20' from tower where
it enters a buried pvc conduit that travels 150' to house, then up to second
story shack. Where nothing is grounded, except by virtue of house AC
wiring - a bad I know (not mine either).
3. Ground current from the tower strike most likely entered the coax
feedlines at the disconnect point as they entered the pvc conduit then
traveled on into house.
4. House current also took huge jolts, zorching all kinds of connected
equipment, phones, tv's etc.
5. Outbuilding with radio equipment connected took huge hit, ball lightning
inside room fried test cords connected to nothing, hanging on test bench,
where the leads touched tile floor, huge blow-out of tile. AC power blew
wall warts across room, computers next to each other had .22 rifle bullet
sized hole between them. Equipment in this bldg was grounded, and some that
was was damaged, others not touched. In short, a massive, multiple
strike-path hit that may not be protectable from - but I realize there was a
lot missing from a good ground picture here also.

Jack

Hi Jack,

You know, it sounds like the lightning hit your house/out-building and
went toward the tower.

73's
Richard Clark, KB7QHC

Richard Clark wrote in message . ..
On Mon, 26 Jan 2004 21:07:24 -0500, "Jack Painter"
wrote:

Richard, my earlier posts described the grounding my friend, here is quick
summary:

1.Well grounded 100' tower, hundreds of feet of many radials, rods, etc.
Survived many strikes.
2. Feedline from tower's dipole was disconnected about 20' from tower where
it enters a buried pvc conduit that travels 150' to house, then up to second
story shack. Where nothing is grounded, except by virtue of house AC
wiring - a bad I know (not mine either).
3. Ground current from the tower strike most likely entered the coax
feedlines at the disconnect point as they entered the pvc conduit then
traveled on into house.
4. House current also took huge jolts, zorching all kinds of connected
equipment, phones, tv's etc.
5. Outbuilding with radio equipment connected took huge hit, ball lightning
inside room fried test cords connected to nothing, hanging on test bench,
where the leads touched tile floor, huge blow-out of tile. AC power blew
wall warts across room, computers next to each other had .22 rifle bullet
sized hole between them. Equipment in this bldg was grounded, and some that
was was damaged, others not touched. In short, a massive, multiple
strike-path hit that may not be protectable from - but I realize there was a
lot missing from a good ground picture here also.

Jack

Hi Jack,

You know, it sounds like the lightning hit your house/out-building and
went toward the tower.

73's
Richard Clark, KB7QHC

Sounds like it. I'm fairly sure it didn't hit the tower. Or if it did,
it also hit the houses at the same time. You don't get dime size holes
in the house, unless the strike is traveling in the house. I don't
think it's too likely ground currents traveled up the unconnected coax
to the house. It would have gone on to ground at the tower, being it's
well grounded. I think the upstairs part of the house was struck, and
the coax from the drake, along with power wiring was the return to
ground. Note all the damage in the house. Jack, you are one lucky $#^
*#^*@.... It could have burned the house down. The coax to ground
level from the upstairs drake may have routed a good bit of the strike
out to ground. Not enough to save damage though..MK

Jack Painter wrote:
"But I guess the currents in the coax weren`t "near enough equal" in
this case."

Yes, and I can`t guarantee common-mode or equal currents. If the folded
unipole gets zapped, equal or non-equal currents may flow in both
conductors. Induced currents are likely to be differential-mode. But if
they are differential-mode currents, something else likely happens. The
line flashes over.

I seem to be very lucky to never have damage with so many opportunities
for damage. We never lost a transistor radio front end with countless
strikes as evidenced by the pitted antennas. We know the coax arcs in
broadcast stations. Most stations have automatic circuits to kill the
transmitter when the coax arcs.


In medium wave broadcast stations there is almost always a Faraday
screen to keep down the harmonic radiation. It gets countless zaps as
evidenced by pock marks and metal splattered about its shield box.Even
so, the coax gets arcs. When you are on the air, transmitter energy
keeps the arc alive once a transient has struck the arc. Most
transmitters are equipped with a momentary kill relay whose d-c coil
circuit is completed by the coax arc. As soon as the transmitter is
killed, the relay is de-energized and the transmitter returns to the
air.

In the 2-way radio world, the transmitter is going to drop out in a
moment when the mike button is released, or the station was in the
receive mode when the lightning hit and there is no energy to sustain
the arc.

The arc prevents conveyance of the energy to the radio. I never saw a
broadcast transmitter with evidence of lightning inside the transmitter
and we have a good ides that these stations get struck almost every time
a dark cloud passes by.

Best regards, Richard Harrison, KB5WZI

Working as a broadcast engineer at a MW (1390 kHz) station quite a few
decades ago, I have placed myself in the transmitter room so as to be
able to look at the towers as a Summer storm passed. That transmitter
did not have an automatic restore circuit. Well, I served as same.
When I saw the lighting strike the towers, I would reset the breaker.
The tubes (813s as I remember) would take that kind of abuse. My
reflexes were good enough in those days that the listeners hardly knew
anything happened.
That is another trade that has disappeared.
Richard knows! Have him tell about the cooked beasties across the
current shunts.
73 Mac N8TT

--
J. Mc Laughlin - Michigan USA

"Richard Harrison" wrote in message
news:25140-40159FDA-

snip

I seem to be very lucky to never have damage with so many
opportunities
for damage. We never lost a transistor radio front end with countless
strikes as evidenced by the pitted antennas. We know the coax arcs in
broadcast stations. Most stations have automatic circuits to kill the
transmitter when the coax arcs.


In medium wave broadcast stations there is almost always a Faraday
screen to keep down the harmonic radiation. It gets countless zaps as
evidenced by pock marks and metal splattered about its shield box.Even
so, the coax gets arcs. When you are on the air, transmitter energy
keeps the arc alive once a transient has struck the arc. Most
transmitters are equipped with a momentary kill relay whose d-c coil
circuit is completed by the coax arc. As soon as the transmitter is
killed, the relay is de-energized and the transmitter returns to the
air.

In the 2-way radio world, the transmitter is going to drop out in a
moment when the mike button is released, or the station was in the
receive mode when the lightning hit and there is no energy to sustain
the arc.

The arc prevents conveyance of the energy to the radio. I never saw a
broadcast transmitter with evidence of lightning inside the
transmitter
and we have a good ides that these stations get struck almost every
time
a dark cloud passes by.

Best regards, Richard Harrison, KB5WZI