[TowerTalk] Grounding base slab and pier tower bases

[Nick Pair]

Hello Chris,
  Yes I could with the cravat that you MUST provide a low impedance ground path to building ground and a lightning ground system.This path must be direct as possible and all bends radiused with at least a 6" radius. Roof installations are particularly hard to protect without a much larger expenditure for funds in copper! Roof cell sites are usually fed with a 4/0 cu wire to a ground grid at earth level. That being said you have to live with what you have sometimes. 
  With a reasonable ground a device similar to the Nott Ltd. GS-1 (nottltd.com/lightning .html), Ericson Broadcast Sales SC-1 or SC-3(or several SC-3's)
(ebsradio.com/lightning.html) or home built like here:porcupine.w4zt.com will reduce your strike chance by 95% or so. The last 5% is due to the fact that sometimes the charge builds up faster than can be bled off with the discharge array you have. I have also built devices by using 3/8 to 1/2 inch stainless steel cable one foot long in a compression one hole lug connector (or crimp if you have access to large enough crimper) on a U-bolt with galvanized or ss saddle on the tower leg. You fray out the cable to create the largest area of points you can. Which ever one you choose, try to place it higher than all antennae. If you must use a rotating member to do this , use a #6 or better insulated wire to the device and to the nearest tower leg with minimum for rotation. Similar metal clamps always.
  Of course YMMV
   
  Good Luck,
  Nick WB7PEK
Christopher J Galbraith <cgalbrai at umich.edu> wrote:
  Hi Nick,

Could you recommend a particular lightning discharge device? The
application is a 40 ft tower on top of a 50 ft building in a relatively
lightning prone area (SE Michigan).

Thanks and 73,

Chris KA8WFC


-----Original Message-----

(snip)

If you lived in a more lightning prone area I'd recommend a lightning
discharge device for the tower top. They do a good job of keeping the tower
potential below where a leader arc can be created preventing a strike from
occurring to the tower and a radius equal to the height around it.

Nick WB7PEK





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