Excitation of aircraft for hardness surveillance using the aircraft's own HF antenna

A technique is reported for testing the electromagnetic radiation hardening of aircraft. The electromagnetic excitation of the aircraft is accomplished by driving the aircraft's high-frequency (HF) antenna at the fundamental resonant frequency of the aircraft. Surface magnetic fields in the range of 1 to 10 mA/m were easily produced with 15 W of RF power. In addition to exciting the fundamental resonances, useful surfaces fields from 10 to 100 MHz were also obtained. The technique is called antenna SPEHS (single-point excitation for hardness surveillance). Measurements of the magnetic field at a prescribed distance from the outside and inside surfaces of hardened apertures, such as window screens and gasketed doors, were made using a multiturn loop sensor and a battery-operated field strength meter allowing the shielding effectiveness to be determined.<
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