Airborne Surveys of USA Urban Areas at 121.5/243 MHz

In situ, aircraft flight measurements were made in 1976 and 1977 by the National Aeronautics and Space Administration (NASA) of the radio-frequency environment over USA urban areas within the emergency distress search and rescue frequency bands at 121.5 and 243.0 MHz. This paper analyzes test results reported previously1-3 for USA East Coast and Midwest flight surveys; presented also are test results obtained in May 1977 for the USA West Coast during the NASA, ASSESS-II, Space Shuttle/Spacelab simulation aircraft flights. The USA West Coast flights include data at 121.5/243 MHz during an extensive series of aircraft-flyover passes for the Los Angeles, CA urban area. The USA East Coast/Midwest measurements show correlation with population count.