IIRC you tie the coax shield to the tower at its base for two reasons, with
a kinda common thread.
1) To eliminate any possible side flashes through the coax's outer
insulation, thereby saving the cable.
2) Connecting the shield to one of the lowest potential points, thereby
draining a good bit of the strike to closest earth ground.
Not tying it to the tower base is like connecting a meter probe to the
highest potential point, the point of the strike, the top of the tower, and
bringing that potential into your shack to the meter, all of your expensive
equipment so that it can measure the full effect of the strike... POOF!
Stan
-----Original Message-----
From: Roger (K8RI) on TT
Sent: Thursday, October 10, 2013 9:06 AM
To: towertalk@contesting.com
Subject: Re: [TowerTalk] Connecting Tower to Ground Rod
On 10/10/2013 8:09 AM, Pete Smith N4ZR wrote:
Does this standard apply even if, as in my case, the tower is 190 feet
from the house entrance?
The farther the antenna, the less the effect, See the Polyphaser page.
But you do want to provide a better path to ground at the tower to
prevent the lightening from coming into the house.
Many of us also ground the coax shield to the top and bottom of the tower.
Does it need to be a direct, dedicated connection, or could a hardline
shield, for example, be used for the tower to house electrical service
ground connection. In cross section, even LDF4-50A is a lot beefier
than >#6.
Using the coax is usually not considered good practice unless the tower
is a long way out.
73,
Roger (K8RI)
73, Pete N4ZR
Check out the Reverse Beacon Network at
http://reversebeacon.net,
blog at reversebeacon.blogspot.com.
For spots, please go to your favorite
ARC V6 or VE7CC DX cluster node.
On 10/9/2013 11:11 PM, GARY HUBER wrote:
National Electrical Code 250.94 will apply to the Rohn Tower and
grounding. A minimum of #6 copper is required for bonding the tower and
ground to the electrical service ground. With the galvanized tower you
don't want a direct copper and galvanizing connection as when wet there
will be electrolytic corrosion. Stainless Steel, and Aluminum are the
most commonly used metals which can be used to isolate the copper wire
from the galvanizing.
NOTE: this BONDING of GROUNDS is the minimum REQUIRED for electrical
safety. It is NOT adequate for the dissipation of a direct lightning
strike.
73 ES DX,
Gary -- AB9M
-----Original Message----- From: Michael Warren
Sent: Wednesday, October 09, 2013 5:50 AM
To: towertalk@contesting.com
Subject: [TowerTalk] Connecting Tower to Ground Rod
What standardized method can I use to connect the base of a Rohn 25 to a
ground rod driven into the ground very near the base?
Michael Warren
Ka5rej
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