A Study on Electrostatic Induction Current for Noise Suppression

Radio noise generated by the ignition system of internal combustion engines is primarily caused by the capacitive discharge current flowing in the ignition circuit when the spark occurs at spark gap. It is known that suppression of the capacitive discharge current usually effective in reducing the radiated ignition noise level. [1]*

However, with exposed engines such as outboard marine, motorcycles, and particularly, in devices with long metal bodies, the radiated level peaks at a frequency which is determined by the length of the metal body.

The authors found that the phenomenon described above could be explained by assuming electrostatic induction current. This was based on the noise voltage from the ignition system to the device. This paper intends to report the findings of this research.