Starfish Prime was a high-altitude nuclear test conducted by the United States of America on July 9, 1962, the explosion took place 400 kilometers (250 miles) above Johnston Island in the Pacific Ocean.
About 1500 kilometers (930 statute miles) away in Hawaii, the electromagnetic pulse (EMP) created by the explosion was felt as three hundred street lights failed, television sets and radios malfunctioned, burglar alarms went off and power lines fused. On Kauai, EMP shut down telephone calls to the other islands by burning out the equipment used in a microwave link.
Thanks — there would be some effect but I am still skeptical as to the effect being total. It’s just that I’ve worked with equipment that pulsed kilo-amps, and also had to help condition high-lightning hit environments.