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. Volume 1 of this report summarized the measured distributions of pulse, interrogation, and suppression rates with received power. This volume presents specific characteristics of the sources of the interrogations observed from the air dUring this flight. These characteristics include the identities of 46 of the interrogators, the approximate locations of 22 unidentified interrogators, the interrogation repetition interval (PRI), scan period, and mode interlace of all interrogators, and the radiated P1, P2, and P3 levels in the form of antenna patterns for six selected interrogators. It was found that approximately 40% of the interrogators employ the standard AAC or 2ACA mode interlaces while 20% transmit no Mode C interrogations. The distributions of PRI's and scan periods were found to be relatively free of bunching which would cause undesired synchronization effects. The antenna plots measured from the air show relatively large scan to scan variations due to aircraft motion. In addition, some of the interrogator sites were found to suffer from reflections and sidelobe punch-through effects.