We're on a tower that had no air terminal. We'd lose gear occasionally.
Owner added an air terminal bonded to the top section. The frequency of
lost gear didn't change much. They ran a conductor from the air terminal
all the way down to the grid and we haven't lost anything since, ~2 years.
We were on another tower for years and always lost gear. 500' FM, cell,
paging. Lots of shit. Halo air terminal on top, 2/0 coming down. We
abandoned it because every year, every single piece of copper on the
ground to about 10 feet up the tower would be missing. It would not be
replaced until the fall. Then it was all gone again the next spring. Lot
of good it does in the winter.
On 7/25/2017 12:38 PM, Paul McCall wrote:
Lewis,
On option 2, if you are just leasing space on a tower such as Crown
Castle, etc., I have doubts that they would allow me to install the 8’
rod at the top and run the 2/0 down the tower. So, would you, just do
a 2/0 starting at your equipment area, bond to the tower at that
height, and go down from there?
On the “bonding everything together” scenario, if the tower ground is
not as good as the other grounds going down the tower (mine, the
cellular companies, etc.) won’t the differential in impedance cause
the lightning to 1) likely take the lesser impedance path down and/or
2) have the voltage not rise and fall together and bad things happen
from that?
Paul
*From:* Af [mailto:[email protected]] *On Behalf Of *Lewis Bergman
*Sent:* Monday, July 24, 2017 1:47 PM
*To:* [email protected]
*Subject:* Re: [AFMUG] Tower Top Grounding discussion
On 1. it will be really difficult to completely isolate a piece of
equipment unless it is designed to float but good luck. If you are
truly going to isolate everything from ground then you won't need to
worry about #2 as all will float. You should check that the antenna
you are using don't require a ground plane.
On 2. I Cadweld a 2/0 jacketed to an 8' rod at the top of the tower,
not isolated. I then bond (15 ton Hydraulic Crimp) it to a bus bar 5'
below the top for equipment grounds. Anywhere else there is a cluster
of equipment I also put a bus bar. I then take that 2/0 to the bottom
to the last bus bar and then into the ground ring.
1. *Wondering what materials people are using to isolate their
mounts?* What is sufficient? Would the rubber from a thick
radiator hose be enough to keep the lightning from coming
through? Double thicknesses?
One consultant recommended starboard, but I am not sure how I will
craft that into a work piece that would mold around a tower leg
and be able to grip it.
2. *What size wire should be going down the tower to bond to my
tower / electrical ground? *
I am assuming it should be insulated but is normal THHN jacketing
enough to have it truly isolate from something jumping over or
does it have be in conduit.
Paul
Paul McCall, President
PDMNet, Inc. / Florida Broadband, Inc.
658 Old Dixie Highway
Vero Beach, FL 32962
772-564-6800 <tel:%28772%29%20564-6800>
[email protected] <mailto:[email protected]>
www.pdmnet.com <http://www.pdmnet.com>
www.floridabroadband.com <http://www.floridabroadband.com>
