Another EMC resource from EMC Standards EMI Stories 476 to 570 Helping you solve your EMC problems 9 Bracken View, Brocton, Stafford ST17 0TF T:+44 (0) 1785 660247 E:
[email protected] EMI Stories 476 to 570 476) Another lightning story The Broward County (Florida) Civil Defense office had a 180 foot radio tower that was several years old before it was finally hit by lighting (this was many years ago). It turns out the tower was not grounded. The lightning came down the heliax coaxial cables, about 2 inches in diameter (no cm back then), into the building. One of the (vacuum tube, remember those?) VHF radios looked like the speaker grille was hit by a fist from behind. The CD director's telephone was melted on the desk. All the electrical outlets were burned and the air-raid siren relay was welded ‘on’. The siren activated and would not turn off. The only person in the office was a secretary who knew nothing about electricity. I think she must have aged 10 years in 2 seconds that day. I was in high school at the time and came to realize at a tender age that there is no such thing as a ‘lightning protector’. (Copied from: “Another lightning story” in the thread “Danger and Power of Lightning”, posted on
[email protected] by Douglas C. Smith, 2nd April 2002.) 477) Black Hawk helicopter crashes In the mid 1980s, the US Army experienced 29 crashes of its UH-60 Black Hawk helicopters, at least five of which were believed to be due to RFI.