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Reducing Radio Equipment Lightning Damage

May 3rd Fact-of-the-Day

Electrical pulses induced in antenna systems by lightning have very fast rise and fall times. They consequently have spectral frequency components that extend from near DC to the top of the radio frequency spectrum. However, most of the electrical energy is concentrated below 1 MHz. The energy reaching radio equipment via antenna feed-lines can be greatly reduced by designing antenna and radio feed-line coupling units to have high attenuation below 1 MHz, or where radio equipment operates below 1 MHz, by designing antenna and radio feed-line coupling units to selectively pass only the minimum bandwidth needed. A simple blocking capacitor connected in series with a coax center conductor can be chosen to have very little effect on desired HF signals while greatly attenuating lightning energy passed to radio equipment. A series capacitor obviously won't provide the amount low-frequency attenuation that is possible with more complex filters, but it is a simple measure that can significantly reduce the risk of radio equipment damage. ©2005 Martek International All rights reserved.

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