Measurement of RF (Radio Frequency) Fields Associated with ISM (Industrial, Scientific and Medical) Equipment as It Relates to Aeronautical Services

摘要

Described are the RF field measurements of four Industrial, Scientific and Medical devices to characterize the fundamental and 4th harmonic radiation from these devices according to FCC Part 18 and CISPR Publication 11 and 11A. The effects of the 4th harmonic radiation is considered with respect to ILS localizer receiver suceptability. The testing was performed at an open field test site with measurements made on the ground and at elevation angles from 45 to 75 degrees. Additionally, an aircraft equipped with calibrated antennas was flown over the ISM device to determine the RF fields radiated overhead at the 4th harmonic of the fundamental operating frequency. The four ISM devices consisted of one with 25 kW power output, two with 2 kW power output, and one at 3 kW power output. Results indicate that RF fields (at ILS localizer frequencies) of 20 to 40 dB above FCC limits can exist as a result of ISM equipment 4th harmonic emissions in the vicinity of ISM equipment. Co-channel emissions from ISM devices on localizer frequencies can produce CDI deviations in excess of 5 micrograms at the missed approach point for certain locations of ISM equipment. (Author)