I did a lot of lightning protection for composite aircraft. After initial losses on my towers, here's our basic system:
1. All ethernet cables inside or out must be shielded. Ethernet is a high impedance signal that lightning can couple into easily. We also prefer gel filled cables for outdoor work. "water proof" non-filled cables aren't. Each end of these cable shields must be terminated to ground. 1.a Surge protection at entrance to NOC for all CAT5 / Coax. Polyphaser rocks for RF. Again, all of this must go to the ground ring with #2 copper. Between antennas at the top and any RF gear at top, polyphaser again. Keep it out of the radio. 2. Ground ring around tower and NOC. We are in clay, so we have about 100 8 ft ground rods interconnected with #2 sold tinned copper via cadweld. Stingers come off these rings for equipment in the NOC, and to each leg of the tower. 3. Up the tower, 2 #2 stranded conductors. One end tied to the ring at the bottom, the other to solid tinned copper ground plates at each boom elevation. Each boom grounded to the plate via cad weld. Ground rod at top of tower grounded to same plate. Lightning dissapaters grounded to same plate. 4. Tower legs, booms, and other bolted together structure is not a proper ground. 4.a Water towers (metal) are usually very well bonded. They make good ground interconnects since they are welded. 5. Large whole building surge protection at utility power entrance. This must tie to the same ring. 6. UPS everything or DC power everything. 7. Small prayer when storms come seems to help! That said, I've seen a direct strike hit with so much energy that it blew a 1 foot whole through the foundation! Marco -------------------------------------------------------------------------------- WISPA Wants You! Join today! http://signup.wispa.org/ -------------------------------------------------------------------------------- WISPA Wireless List: wireless@wispa.org Subscribe/Unsubscribe: http://lists.wispa.org/mailman/listinfo/wireless Archives: http://lists.wispa.org/pipermail/wireless/
