On Two Methods of Measurement of Ignition RFI Suppressor Effectiveness

Two methods for measurement of the effectiveness of anti-interference resistors, spark plugs, cables, etc., used for suppression of radio noise generated by vehicle engine ignition systems are described and mutually compared. One of them requires a standard vehicle and open-field test facility, and the second one is an indoor method and is based on application of a standard model of ignition installation. The indoor method saves over 90 percent of the measurement time in comparison with the other. Ideally, both methods would give the same results. Practically, however, the results of measurements may be different due to the influence of several factors, some of them uncontrollable. These factors are investigated theoretically and experimentally in the paper. The experimental part is based on about 400 pairs of measurement results (which are drawn from about 4000 original results) concerning 19 different suppressor sets, 12 vehicle types, and 23 frequencies from the frequency range 30 to 1000 MHz. The experimental data originate from three European laboratories.