Experimental swept-frequency tropospheric scatter link

An experimental swept-frequency tropospheric scatter link, with a path length of 194 miles, has been established in France between Cholet and Corbeville. The transmitter (designed by Compagnie Générale de Télégraphie Sans Fil) sweeps in a nearly linear manner from 3100 to 3600 mc and back to 3100 mc at about 10 cps. The average transmitted power is 250 watts. The receiver and data display (designed by Airborne Instruments Laboratory) sweep in synchronism with the transmitter. The synchronizing signal is derived from the carrier frequency of a broadcast station (Paris-Inter). The receiver is designed to track swept signal amplitudes down to about 4 db above noise level, and after severe fades, to reacquire signals larger than 6 db above noise level in about 1 to 2 milliseconds. Received signal amplitude is presented as a simultaneous function of frequency and time. Preliminary data obtained from the link indicate that privileged transmission frequencies exist at all times in this band at which the transmission level is about 10 db above median. The preliminary data gathered from the link are described, as well as general design features of the system.