Interesting, You made me look. (made me Look up coherer, that is).
An invention of Sir Oliver Lodge for detecting rf.
Your idea of using it as a lightning protection device seems to be a
misapplication.
But like I said, until now, I never heard of it.

"John Smith" wrote in message
...
For a receiving antenna, a coherer provides excellent lightning
protection.

Unfortuantly, on a transmitting antenna, the rf would immediately make
the coherer conductive and a direct short to ground (perhaps very low
QRP power could be used?)

One can easily be construted with a bottle filled with metal filings,
two bare wires are inserted into the filings (not touching and
seperated by a substantial amount of the filings), one wire goes to a
good earth ground, the other to the antenna.

If the coherer shorts to ground it only needs to be shaken to reset (I
would suspect in a real lightning strike the metal would be fused,
quite possibly even vaporized.)

John

"Jerseyj" wrote in message
...
Hi all,
For years I lived in an apartment and just had antenna's in the
attic ,
but now having moved to a house in a few months I'll be putting up a
10-160 wire type antenna in my trees. Given the recent spate of
serious
thunderstorms, and the accompanying lightning, I'm a bit concerned
about
properly grouding the antenna so that I don't fry the house *smile*.
I
know about some articles on the ARRL site, but was wondering if
anyone
else had some ideas or pointers on how to practically do this ?

Jerry

"Ham op" wrote in message
...
Thierry wrote:

SNIPPED

HI,

Good to read :
http://www.astrosurf.org/lombry/qsl-...protection.htm

Personnaly, in my humble opinion, under thundery weather there is no
better
solution than unpluging all electronic devices...

Thierry, ON4SKY

Agree! But, I still lost an ICOM 756 Pro II when disconnected from
antenna,
and had the power supply unplugged. A ground loop in the external ground
on
the 756 and the power supply, where 12 volt return is tied to chassis,
caused
damage to the power connector on the 756 and fried the 756 internal
cabling and
circuit boards were carbonized.

I'm still waiting for my insurance settlement.

MORAL: Lightning does what lightning does!


For sure, as soon as there is a sink, a path of lower resistance, the
lightning will find it and will follow it to your most expensive accessory..
This canal can be the coaxial, the house cabling system, even yourself if by
mistake you touch a metallic device during the thunder. Even the ground as
state in my article can be an excellent way for the lightning to strike your
installation. Hence it is better to entrust this installation to experts.

So I when I say to unplug all devices, this is *all* cabling system,
including grouding.

Usually the insurance do an excellent job and you should be able to rebuy
all your defective devices.

Good luck.
73
Thierry, ON4SKY

Does anyone know of cases where houses have fried as a consequence of
ham wire antennas, "protected" or otherwise?

We all know of cases where electronics gets zapped but Jerry is
concerned about his house.

Be interesting to hear of actual cases, wouldn't it? Statistics would be
even better, but I won't hold my breath.

Chuck

Jerseyj wrote:
Hi all,
For years I lived in an apartment and just had antenna's in the attic ,
but now having moved to a house in a few months I'll be putting up a
10-160 wire type antenna in my trees. Given the recent spate of serious
thunderstorms, and the accompanying lightning, I'm a bit concerned about
properly grouding the antenna so that I don't fry the house *smile*. I
know about some articles on the ARRL site, but was wondering if anyone
else had some ideas or pointers on how to practically do this ?

Jerry

Chuck wrote:
"We all know of cases where electronics gets zapped but Jerry is
concerned about his house."

Ben Franklin promoted lightning rods to protect people and houses before
electronics was. These rods would not have sold had they not seemed to
work. Tell me a drowning man will grasp at straws!

Best regards, Richard Harrison, KB5WZI

Chuck wrote:
"We all know of cases where electronics gets zapped but Jerry is
concerned about his house."

I`ve worked in many protected structures struck repeatedly by lightning
to their air terminals, rods, and towersm resulting in not one scintilla
of damage to occupants or equipment.

Transportation vehicles are struck by lightning every day and seldom
experience anything inside. An open convertible is not safe in a
lightning strike however.

Best regards, Richard Harrison, KB5WZI

On Mon, 18 Jul 2005 10:59:41 -0500, (Richard
Harrison) wrote:

Chuck wrote:
"We all know of cases where electronics gets zapped but Jerry is
concerned about his house."

Ben Franklin promoted lightning rods to protect people and houses before
electronics was. These rods would not have sold had they not seemed to
work. Tell me a drowning man will grasp at straws!

Best regards, Richard Harrison, KB5WZI


Franklin, defying the gods, performed his kite flying experiment in
June of 1752, and by late June or July, the first "lightning rods"
were installed on structures in Philadelphia. Ol' Ben kinda made up
his own "nec code".

bob
k5qwg

Richard, we both know that a transportation vehicle makes a pretty good
Faraday[sp?] Cage.

Lightning attaching to a wire will instantly vaporize the wire.

Physical damage is generally caused by direct strike. The energy in the
action intergral [I^2*R*dt] generates local heat. The thermal shock
causes the damage. [And fire].

Richard Harrison wrote:
Chuck wrote:
"We all know of cases where electronics gets zapped but Jerry is
concerned about his house."

I`ve worked in many protected structures struck repeatedly by lightning
to their air terminals, rods, and towersm resulting in not one scintilla
of damage to occupants or equipment.

Transportation vehicles are struck by lightning every day and seldom
experience anything inside. An open convertible is not safe in a
lightning strike however.

Best regards, Richard Harrison, KB5WZI

I had the experience of a direct hit to my antenna. It was a 130 foot cage
fed with ladderline. Coax was used the last 20 feet to bring it into the
house.

Inside I had a TS-440, a TS-820 and an MFJ 989C.

The bolt destroyed the side of the antenna that went to the shield of the
coax, the largest remaining piece was about 3" in length with most of it
vaporized. The ladderline was vaporized, the other half of the dipole was
untouched.

The coax split open like a hotdog put in a microwave. The same stroke went
into the electric utilities and blew every electronic device in the house
except a cheap GE clock radio.

A stroke went through the wiring in the ceiling and the explosive expansion
of hot air blew all the vinyl siding off the front and one side of the
house.

The only fire damage was a small burn mark on the shack carpet where the
coax laid on the floor.

All antennas were grounded via the antenna switch and all ham gear was
unplugged. All antennas had blitzbuggs and coiled coax before entering the
house. These were tied to both RF ground and the single point electrical
ground.

What was strange was the stroke following paths along wood beams while
ignoring good conducting copper wires 3 feet away. The only damage to the
ham gear was a burn mark and heat distortion on the rear panel of the tuner.
It's operation was unaffected.



"chuck" wrote in message
ink.net...
Does anyone know of cases where houses have fried as a consequence of
ham wire antennas, "protected" or otherwise?

We all know of cases where electronics gets zapped but Jerry is
concerned about his house.

Be interesting to hear of actual cases, wouldn't it? Statistics would be
even better, but I won't hold my breath.

Chuck

Jerseyj wrote:
Hi all,
For years I lived in an apartment and just had antenna's in the attic ,
but now having moved to a house in a few months I'll be putting up a
10-160 wire type antenna in my trees. Given the recent spate of serious
thunderstorms, and the accompanying lightning, I'm a bit concerned about
properly grouding the antenna so that I don't fry the house *smile*. I
know about some articles on the ARRL site, but was wondering if anyone
else had some ideas or pointers on how to practically do this ?

Jerry

Ham Op wrote:
"Physical damage is generally caused by direct strikes."

Lightning can produce awsome distruction from its millions of volts and
thousands of amps. Stories about it are informative, amusing, and
abundant.

Damage is mostly avoidable. High towers are nearly certain to be struck
repeatedly in passing thunderstotms. I`ve worked in medium wave
broadcasting, Short wave broadcasting, land-mobile radio, aircraft
radio, and microwave relay systems aplenty. I worked decades with a
worldwide corporation that had towers across the U.S.A. and several
other countries in the world. That corporation had its many towers
fitted with inverted Copperweld ground rods at the top to serve as
lightning rods to take most of the hits the towers received. At their
bottoms, the towers` lightning energy was shunted off to the earth
through ground rods driven into the soil around the towers. It worked.
There was no vaporized coax, tower lighting wires, or anything else.

We had to operate perpetually. We couldn`t pull the switch and throw the
coax out the window, even if someone were on hand to do so.

Evidence of lightnong strikes were the small pits it made in the
lightning rods.

Best regards, Richard Harrison, KB5WZI

I understand the concept, but if I have a wire antena , going to ladder
line, the trasitioning to coax, all outside, with the coax finally
snaking into the house and hooking up to the antenna tuner...

Where would I put grounds, how would I attach them, etc...???

I'm having trouble visualizing doing this grounding without it affecting
the antena performance.

Jerry

(who was generalizing when talking about house damage, but was really
just looking for help with ideas for grounding and thank you all who
have responded)

In article ,
(Richard Harrison) wrote:

Ham Op wrote:
"Physical damage is generally caused by direct strikes."

Lightning can produce awsome distruction from its millions of volts and
thousands of amps. Stories about it are informative, amusing, and
abundant.

Damage is mostly avoidable. High towers are nearly certain to be struck
repeatedly in passing thunderstotms. I`ve worked in medium wave
broadcasting, Short wave broadcasting, land-mobile radio, aircraft
radio, and microwave relay systems aplenty. I worked decades with a
worldwide corporation that had towers across the U.S.A. and several
other countries in the world. That corporation had its many towers
fitted with inverted Copperweld ground rods at the top to serve as
lightning rods to take most of the hits the towers received. At their
bottoms, the towers` lightning energy was shunted off to the earth
through ground rods driven into the soil around the towers. It worked.
There was no vaporized coax, tower lighting wires, or anything else.

We had to operate perpetually. We couldn`t pull the switch and throw the
coax out the window, even if someone were on hand to do so.

Evidence of lightnong strikes were the small pits it made in the
lightning rods.

Best regards, Richard Harrison, KB5WZI