Field Strength of Motorcar Ignition between 40 and 450 Megacycles

Measurements of motorcar-ignition peak field strength were made on frequencies of 40, 60, 100, 140, 180, 240, and 450 megacycles. Propagation was over Long Island ground and the receiveng antennas were 35 feet high and 100 feet from the road. Under these conditions, the average field strength varied about 2 to 1 over the frequency range. Curves show the maximum field strength versus frequency for 90, 50, and 10 per cent of all the measurements. Vertical and horizontal polarization are compared showing slightly greater field strength, in general, for vertical polarization. New cars, old cars, and trucks are compared showing no large differences of ignition field strength. Some of the factors involved in motorcar-ignition radiation are mentioned. Theoretical propagation curves are included and the measuring system is briefly discussed.