However Bob, having been shunted to ground by good tower grounding the
jump voltage is far smaller than that required to jump a few thousand
feet. But its far more than equipment can stand on its own. So a foot or
two of gap has proven adequate here. And since my tower is the highest
thing within a mile in all directions I'm sure (by the flash and click
matching in time) that its taken several direct hits a year without
damage to ham gear or house wiring (its rather difficult to add a proper
ring ground bus to a rental house). The COMBINATION of grounded tower,
grounded house and gap between makes a more effective attenuator of
lightning than all the ground rods on earth because each has a
significant resistance and more inductance and the earth itself has
considerable resistance.
I've been hit without that gap and suffered damage all over. So I remain
with separated house and tower grounds with a gap except when using the
tower mounted antennas. It works best here in the Iowa plains.
73, Jerry, K0CQ
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Entire content copyright Dr. Gerald N. Johnson, electrical engineer.
Reproduction by permission only.
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