Summary
Airborne measurements of the Air Traffic Control Radar Beacon System (ATCRBS) 1030 MHz uplink environment due to ATC ground interrogators are described. The measurements were made using a special purpose airborne sensor-recorder during a flight from Boston to Washington (at 8500 feet) and back (at 17,500 feet) on 16 December 1977. Data were recorded at 24 locations between Boston and Washington and processed to obtain distributions of pulse, interrogation, and suppression rates with received power. The most numerous contributors to the uplink pulse environment are omnidirectionally radiated suppression pulses. The overall average suppression rate is approximately 600 per second. The suppression rate is relatively independent of altitude but there are wide variations in the suppression rate from one location to another. Interrogation rates increase with altitude but do not vary significantly from location to location except near interrogators without sidelobe suppression. The overall average rate of receipt of Mode A plus Mode C interrogations is approximately 75 per second at an altiude of 8500 feet and 100 per second at an altitude of 17,500 feet.