APD Measurements of V-8 Ignition Emanations

Amplitude-probability-distribution (APD) data are presented for ignition emanations from V-8 engines of used motor vehicles. Outputs from both single and multiple engines running at 1500 rpm were measured with an omnidirectional antenna over the frequency range from approximately 20 MHz to 1 GHz. In each case, the antenna was oriented similarly with respect to the vehicle(s)-vertical, height 3 m, distance 10 m. Results are presented on Weibull-distribution sheets and compare favorably with those of Hsu et al. [1] using a different technique. On each sheet, APD distributions are given for various received bandwidths between 1 and 300 kHz. For the larger bandwidths, curves are straight lines with large negative slopes. At narrower bandwidths and for multiple vehicles, slopes are less steep. Major conclusions from the APD results include the following. 1) Although overlapping of successive pulses at a detector becomes more prominent at narrower bandwidths, measurements are still valid and representative for a given bandwidth. 2) Measurements indicate good repeatability. 3) Curve shapes are essentially independent of tuned frequency, but do depend upon bandwidth and number of vehicles. 4) Amplitudes are functions of tuned frequency and number of vehicles.