Institute for Telecommunication Sciences
the research laboratory of the National Telecommunications and Information Administration

Robert J. Matheson

Abstract: Measurements of the amplitude probability distributions and the average crossing rates of the electromagnetic noise radiated by automotive ignition systems were made at 30 MHz, 47 MHz, 147 MHz, 224 MHz, and 445 MHz. The ignition noise from a single car and a 12-car matrix were each measured in a 10 kHz bandwidth, using a field-intensity meter, a DM-4, a desktop calculator, and an X-Y plotter. The DM-4 is an instrument built by NTIA to measure amplitude probability distributions and average crossing rates. Numerical integration of the amplitude probability distributions was used to determine the rms, the average, and the average logarithm of the envelope of the measured noise.

Keywords: automotive ignition noise; electromagnetic noise; noise measurement; amplitude probability distribution

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