IMPROVED LIGHTNING PROTECTION FOR RADIO TRANSMITTER STATIONS

摘要

Each year, in the United States alone, lightning is responsible for the injury or death of hundreds of people and millions of dollars in property damage. Radio transmitters that utilize tall antenna towers are particularly vulnerable because these towers closely resemble lightning rods, designed to conduct lightning energy to ground. Even distant lightning strikes can generate powerful electromagnetic waves that induce energy into transmitting antennas and power distribution systems. The actual strike incidence varies widely with general geographic location and is also affected by the local topography, the height of the transmitter mast, and the routing of the incoming power lines.rnUnless definite precautions are taken, such strikes can cause injury to personnel and damage to equipment. The transmitter's final RF amplifier, the ac line rectifiers and embedded software programs are particularly valnerable. A highly reliable transmitter in the laboratory environment can become prone to failure in a real-world situation.rnThis paper presents a simplified summary of lightning data from several technical sources in a manner which permits a quantized approach to the problem. It then goes on to discuss protection principles, and concludes with definite system recommendations. Implementation of these recommendations can also provide significant improvement to the overall stability of the transmitter station, by eliminating the harmful effect of antenna current return paths flowing through sensitive circuitry in the transmitter building. It is not intended as a rigorous treatise on lightning because such in not helpful for the intended task of deducing engineering solutions. Also, where source data is conflicting, judgemental decisions have been made without discussion by the author.