[TowerTalk] Lightning arrestor in towers
K8RI on TT
k8ri-on-towertalk at tm.net
Sun Jun 19 19:33:00 PDT 2011
On 6/19/2011 7:58 AM, HansLG at aol.com wrote:
> I just wonder if I can get some input.
> I was thinking putting a "stick (conducting)" on top of my tower well above
> any other installation. Connect the "stick" to a heavy wire that is well
> grounded in the other end. The idea is that a lightning preferable will hit
> the "stick" and be safely conducted to the ground similar what you do with
> a house.
If you note the top antennas in
http://www.rogerhalstead.com/ham_files/Tower29.htm they are 30 feet
above the top of the tower. The cross boom, antennas, and mast have
taken a number of direct hits. It's difficult to really know from
neighbors reports which antennas or where on the tower any specific bolt
struck. there is enough information to know that the *stuff* "on top"
has taken more than one or two hits. It's also obvious that some strikes
were to lower antennas.
All coax shields are grounded to the tower at the top and the bottom.
They are also grounded where they enter the house through a grounded
bulkhead as well as where they enter the shop. Each leg of the tower is
tied into the ground system which radiates out from the tower as well as
running to those grounded bulkheads. Also each tower ground is tied
into the over all ground system. The shop and house each have their own
electrical service and grounds, but those too are tied into the overall
ground system as the computers in the house and shop are tied togather
via CAT5e or CAT6 and the ham stations all tied together as each station
feeds antennas on each tower. Were the system grounds not all tied
together lightning strikes would tend to follow either coax, control
cables, network cables, or telephone cables from one building to the other.
The mast at the top of the towers goes through at least 2 thrust
bearings that provide side support, but no vertical load support. There
are 4 coax runs from the antennas mounted on the mast. These run through
bulkhead connectors at the top of the tower. So the mast serves as a
lightning rod "of sorts". It's more a case of every thing being well
The ground system itself consists of 32 or 33 8' copper clad, steel
ground rods Cad Welded (TM) to over 600 feet of bare #2 copper wire.
> A few days ago I did have a hit on my house and the lightning protection
> worked except for a surge protector and a battery charger located near the
> corner that was hit. Everything else survived.
> Hans - N2JFS
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