X-ray emission from broadcast transmitters

During the past few years amplitude-modulated transmitters employing efficient pulse-width modulators have come into common use. These transmitters are reliable, relatively insensitive to vacuum tube characteristics, and offer excellent audio fidelity. Their architecture requires, however, supply voltages in the 20-30-kV range, which greatly enhances the production of ionizing radiation in the form of X-rays. Recent analysis by Voice of America indicates that these X-rays are being emitted in short, high-intensity bursts focused into broad radial beams. The general aspects of ionizing radiation of interest to communications engineers are reviewed. The spectral and time-domain characteristics of X-ray radiation from transmitters are examined, a method for estimating fault-condition radiation values is suggested, and the findings of the Voice of America are discussed