Service Range for Air-to-Ground and Air-to-Air Communications at Frequencies above 50 Mc

Propagation aspects of air-to-ground and air-to-air communications are analyzed. Contours of constant received signal strength are shown in the form of lobes for various frequencies. It is shown that for systems with equivalent transmitted power, ground-antenna height, and transmitting- and receiving-antenna gain the service range decreases as the frequency is increased. This is due primarily to a decrease in the absorbing area of the receiving antenna and to a larger number of nulls in the lobe structure arising from interference between direct and ground-reflected waves. Ground-station antenna-height diversity and tilted-array ground-antenna systems are discussed as a means of improving coverage as the operating frequency is increased.