Field-Strength Measurements of Microwave-Oven Leakage at 915 MHz

Measurements of electric field strength of microwave emissions from microwave ovens in the 915-MHz industrial-scientificmedical (ISM) band are reported. Field strengths were determined at 10 and 1000 ft under laboratory conditions and in the vicinity of two large condominium buildings, containing 385 ovens, in Ft. Lauderdale, Florida. Monitoring equipment consisted of dipole and log-periodic antennas feeding the input of a spectrum analyzer which was interfaced to a minicomputer system for automatic data acquisition and analysis. Under controlled conditions, the tested oven produced maximum field strengths of 123.5 dBuV/m and 81.0 dB,uV/m at distances of 10 and 1000 ft, respectively. Fields as high as 79.0 dBuVm were observed at the Florida location, approximately 500 ft from the buildings. Additional measurements were made of band occupancy and the effects of load placement in the oven, orientation of the oven, and polarization of the emerging fields.