hi


a friend of mine might get permission to put up an antenna or two on top
of his apt building about 30 stories up mostly flat roof

the other buildings for a good distance are less than 6 stories

so i was wondering how do you protect something like that from
lightning

even if he disconnects the rig from the antenna you've still got well
over 100ft of coax with a lot of charge


there are no other antennas up there just a red flashing light ontop
of the elevator room

what is typically done?

running a heavy cable to ground downside the buidling is out

i guess it wouldn't be 'code' to grab a electrical ground out of the
elevator room, and i guess equally bad to tie into the steal girders
in there

so how do the pro's do it??

ml wrote:
hi


a friend of mine might get permission to put up an antenna or two on top
of his apt building about 30 stories up mostly flat roof

the other buildings for a good distance are less than 6 stories

so i was wondering how do you protect something like that from
lightning

even if he disconnects the rig from the antenna you've still got well
over 100ft of coax with a lot of charge


there are no other antennas up there just a red flashing light ontop
of the elevator room

what is typically done?

running a heavy cable to ground downside the buidling is out

i guess it wouldn't be 'code' to grab a electrical ground out of the
elevator room, and i guess equally bad to tie into the steal girders
in there

so how do the pro's do it

The building has no lightning protection in place now?

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ml wrote:
"A friend of mine might get permission to put up an antenna or two on
top of his apt building about 30 stories up. mostly flat roof."

Likely the building already has air terminals (lightning rods) around
its periphery. These probably are connected with heavy cable to the the
steel skeleton of the building. If not, that is another story.

Your friend needs to directly ground his antennas to the same system as
the air terminals for lightning protection.

Best regards, Richard Harrison, KB5WZI

In article ,
chuck wrote:

ml wrote:
hi


a friend of mine might get permission to put up an antenna or two on top
of his apt building about 30 stories up mostly flat roof

the other buildings for a good distance are less than 6 stories

so i was wondering how do you protect something like that from
lightning

even if he disconnects the rig from the antenna you've still got well
over 100ft of coax with a lot of charge


there are no other antennas up there just a red flashing light ontop
of the elevator room

what is typically done?

running a heavy cable to ground downside the buidling is out

i guess it wouldn't be 'code' to grab a electrical ground out of the
elevator room, and i guess equally bad to tie into the steal girders
in there

so how do the pro's do it

The building has no lightning protection in place now?

i might have over looked the obvious, i didn't get to walk the
roof, but looking at it from the ground or building apartment to the
other building it's 1 of 2 buildings (twins) no obvious lightning rods
that i can see any place thou i can't totally see the roof

the only thing i can clearly see is 2 red lights on a short pole on the
wall of the elevator room


i'll certainly look for lightning protection if it's there great if not
i dunno

just seems to me a really really tall building out in the open, with
a ham antenna ontop can certainly get it's share of zaps


thanks all

On Sun, 18 Feb 2007 21:00:23 GMT, ml wrote:

there are no other antennas up there just a red flashing light ontop
of the elevator room


Hi Myles,

Your friend may stand getting static from the FAA if those red lights
are aeronautical warning lights. If so (and this is just a guess),
then he may be required to light up his mast (as well as paint it).

Checking with authorities might be warranted.

73's
Richard Clark, KB7QHC

ml wrote:
so how do the pro's do it??

The steel structure of the sky scraper is one of the best grounds you
could have. It is effectively a Faraday shield around everything.

You ought to find out where the ground connections for the existing
lighting rods are and use that. If there are no lightning rods around
(shudder) find some structural steel close to your antenna, and bug
(clamp) on to it. I would also suggest following an electrical panel
ground around to see where its ground is. They too ought to be on
building steel.

Good Luck!

Jake Brodsky
Amateur Radio Station AB3A

chuck wrote in
:

ml wrote:
hi


a friend of mine might get permission to put up an antenna or two on
top of his apt building about 30 stories up mostly flat roof

the other buildings for a good distance are less than 6 stories

so i was wondering how do you protect something like that from
lightning

even if he disconnects the rig from the antenna you've still got
well over 100ft of coax with a lot of charge


there are no other antennas up there just a red flashing light
ontop of the elevator room

what is typically done?

running a heavy cable to ground downside the buidling is out

i guess it wouldn't be 'code' to grab a electrical ground out of
the elevator room, and i guess equally bad to tie into the steal
girders in there

so how do the pro's do it

The building has no lightning protection in place now?

Even if it does, this antenna is likely to protrude above its zone.



--
Dave Oldridge+
ICQ 1800667

"ml" wrote in message
...
hi


a friend of mine might get permission to put up an antenna or two on top
of his apt building about 30 stories up mostly flat roof

the other buildings for a good distance are less than 6 stories

so i was wondering how do you protect something like that from
lightning

you don't. you add proper arresters and connect to the existing building
ground to handle the inevitable direct strokes. and don't do it on the
cheap or he may be liable for damage to lots of other stuff when the
lightning follows his transmission line into the otherwise safe building.

In article ,
Jake Brodsky wrote:

ml wrote:
so how do the pro's do it??

The steel structure of the sky scraper is one of the best grounds you
could have. It is effectively a Faraday shield around everything.

You ought to find out where the ground connections for the existing
lighting rods are and use that. If there are no lightning rods around
(shudder) find some structural steel close to your antenna, and bug
(clamp) on to it. I would also suggest following an electrical panel
ground around to see where its ground is. They too ought to be on
building steel.

Good Luck!

Jake Brodsky
Amateur Radio Station AB3A

hate to show my ignorance, but are the ibeams really 'ground'?
usually i've seen them either sitting on concreate squares or on
larger concreate foundation wall like things so i always figured
they'd be rather isolated from ground beside what little connecitivity
was in the concreate itself which i know would carry a lightning
strike, if hit but not the other way around ie higher resistance
so i ponder

same for the electrical pannel ground to be attached to the building
steel ??

i dunno

ml wrote:
In article ,
Jake Brodsky wrote:

ml wrote:
so how do the pro's do it??
The steel structure of the sky scraper is one of the best grounds you
could have. It is effectively a Faraday shield around everything.

You ought to find out where the ground connections for the existing
lighting rods are and use that. If there are no lightning rods around
(shudder) find some structural steel close to your antenna, and bug
(clamp) on to it. I would also suggest following an electrical panel
ground around to see where its ground is. They too ought to be on
building steel.

Good Luck!

Jake Brodsky
Amateur Radio Station AB3A

hate to show my ignorance, but are the ibeams really 'ground'?
usually i've seen them either sitting on concreate squares or on
larger concreate foundation wall like things so i always figured
they'd be rather isolated from ground beside what little connecitivity
was in the concreate itself which i know would carry a lightning
strike, if hit but not the other way around ie higher resistance
so i ponder

same for the electrical pannel ground to be attached to the building
steel ??

i dunno

If the building steel weren't grounded, you'd have serious damage every
time a thunderstorm came along. The building would get struck by
lightning and then it would have to make a path to ground SOMEHOW.
Often, static charges could build up just from wind blowing past a
building. Can you imagine the static discharge of a whole building
against some poor slob who happens to touch it by accident? It would be
deadly...

In any case, most building standards I've heard of do require building
steel to be grounded.


Jake Brodsky
Amateur Radio Station AB3A