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I would suspect a poor grounding system on the tower. If the ground is a
rod driven into the Earth, then the impedance needs to be as low as possible. Once the ground system takes a surge, glass crystalls will form in the dirt on and around the rod. The impedance then climbs and the number of strikes to the tower increase. The amount of impedance in your ground network determines the amount of static charge that can build on the tower and how fast the charge can bleed. The formula for calculating the bleed rate is 5 times (Resistance times Capacitance). The resistance is the ground impedance and the capacitance is the amount of surface area of the tower relative to the air flow over it (think of two plates on a capacitor with a dielectric between them). Any charge above that of the Earth makes that point more likely to get hit by lightning. The tower is only one item to concern yourself about because a floating antenna can be just as bad. Ground everything on the tower during a storm if it is not in operation such as a repeater. Surge arrestors on the antenna feeds then become imparative for repeater installations. A very large grounding system is required to mitigate the potential for lightning strikes on a tower. If a strike does occur, then the grounding structure needs to be able to dissipate the charge back into the Earth very quickly or the ground will be lost until the voltage on the ground falls. Again, R x C for the Earth. Good Luck, Frank N1SIF wrote in message ... I HAD a tower up on the north side of the house for about 15 years, it , top out at about 100feet. I built a 'tilt over' that is 52 feet tall with a mast of about 25, = 77 give or take. been 'up' about 1.5 years and lighting has 'hit' it twice. One was higher, never hit, this one is lower, hit is there anything I can do to 'fix this'? Lost antennas, need to do 'something'. thanks in advance. cl 73 |
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