On Mon, 01 Dec 2008 19:03:48 -0500, ml wrote:

In article
,
wrote:

On Nov 30, 10:15*am, ml wrote:


i always *wonder * what *would be logical to assume * in a *direct *hit *
scenario

thanks

You don't mention what the roof antennas are mounted on.
IE: metal masts, vent pipes, etc?? Well grounded, or not?
If you are depending on the feedlines taking the brunt of the
strike to ground, yes, could be some damage along the way.
I doubt the dipoles would have much trouble, but the J-pole
could well take the strike. Or any other vertical pointy antennas.
That you are grounding at the entry will probably save the
house if you have a good low resistance ground at that point.

But it would be better to have the supporting antenna masts
take the brunt of the strike to ground via good ground wires
or straps if on the roof, or even better, directly planted on the
ground.
You will still have current on the feed lines, but it will be much
less than if they have to carry the whole load.
This is why I've always preferred using a stand alone metal
mast as my support. I'll mount my dipoles slightly lower than
the tip of the mast. Sometimes I'll have ground planes or
verticals on top, but if I do, I always run the coax all the way
down to the base of the mast before leading it to the shack.
I've had two strikes to that mast in the last few years and
had no damage at all. The mast acted as the lightning rod,
and the antennas just floated along for the ride.
I have the coax cables grounded outside the window, and
you can hear an audible arc at the instant of the strike.
So there is current on the lines to ground, but it's not enough
to hurt anything.
But if I used the coax as the only path to ground, I wouldn't
feel near as optimistic it would survive without damage.
And 175 ft is a pretty long path to take if it's not straight
down to ground. You want all those cables snubbed to
ground at a point well before they get to the ICE.
If they dangle from overhead down to the ICE, the potential
will be quite large.

hi thanks very much for responding

I should have mentioned that all the antennas are mounted on heavy
ga metal support masts around 10ft and bolted to a brick wall
of the elevator room

i am up 14 stories building wouldn't let me run any wires to
ground on the outside of the building from the roof wish i could

so currently it's just my ice protectors inside my apt on 4th fl
'grounded' to the elec

That is not going to cut it. You Must have protection "on the roof"
to comply with code. You need lightning arrestors on each feed line
on the roof.


is't really to much i have access to living in an apt, i'l like
to be able to chip the concreate away inside the elevator room to
get at a beam and clamp onto that but they wouldn't allow that
nor penatrating the room to feed the wire out

They are lack electrical knowledge, so apparently do you.


there is a electrical box up there i suppose i might be able to
run a small wire from it to the masts

Not a small wire, you want just as big at the ground wire to the
electrical box, a small wire will not protect.

not sure if code will
allow using elec conduit in an elevator room as a 'ground ' in
this fashion i suspect not

No it does not meet code, not UBC nor NEC.

and the inspector is up there
regularly and not sure how much lightning protection that would
afford maybe bleed al little so a smaller hit

i appreciate your sharing the ideas
thanks

Get yourself a local person knowledgeable in the field.

JosephKK wrote:

...
Get yourself a local person knowledgeable in the field.

Here are my humble thoughts upon this all ... let me warn you, there has
been no extensive testing done, and I live in the central valley of
California--lightening is as rare as diamonds here ...

However, I have run as heavy as #8 wire, fearing protection ...

After much thought, I now have #12, I am sure it will vaporize in a
direct strike (if it ever happens in my lifetime), but those vaporized
particles and molecules will provide a path to ground which the
lightening will continue to follow to complete discharge ... after
which, will need replacing ...

But then, I might have missed something; what are your thoughts?

Warm regards,
JS