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NE-2 Lightning Protection

December 31st Fact-of-the-Day

Sometimes NE-2 neon lamps are used on receiving antennas to provide protection from transient voltages induced by lightning. There are several problems with that. One is the high firing potentials of typical NE-2 lamps. Individual lamp firing potentials vary, but they generally fire at about 90 VDC or 65 VAC. That is a lot of voltage to apply to the input of a sensitive RF amplifier designed to amplify signals in the microvolt range. Current-carrying capacity is another problem. Lightning induced voltages are commonly high enough to flash across any current-limiting series resistor, causing lamp current to greatly exceed NE-2 ratings. Even if the current doesn't cause a lamp to explode or show visible signs of damage, internal sputtering will remove rare-earth coating from the electrodes. That will increase both the DC and AC firing potentials and cause the lamp to provide even less protection next time. ©2004 Martek International All rights reserved.

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