Ignition interference to UHF communication systems

Some quantitative measurements on vehicular ignition noise are reported in terms of the spectral density of radiated power in the vicinity of 900 Mc, to assist in predicting the amount of interference which must be considered in siting microwave communication systems. The median radiated power of the ignition pulses was determined to be −12 dbm and −22 dbm/Mc bandwidth for trucks and passenger cars respectively. Conventional suppression techniques, normally effective at lower frequencies, were found to have no effect. Polarization of the receiving antenna also had no statistical effect. The effects of such interference on the FM receivers and multiplex equipment of a troposcatter communication link were also evaluated. The pulses were audible whenever their received level exceeded the desired signal level.