Microwave propagation over a mountain-diffraction path

Stanford University has been conducting a theoretical-experimental study of obstacle diffraction at microwave frequencies. The experimental program utilizes Mt. Diablo, 36 miles northeast of Stanford, with a height of 3850 feet, as the diffracting obstacle. The path profile is shown in Figure 1. The core of the program is frequency-sweep transmission which permits time-shared study of received power as a function of both frequency and time. The transmitter, a 300 watt carcinotron, is frequency-modulated by a 25 cps sawtooth waveform over a 60 Mc range centered at 3130 Mc. The receiver is swept in a similar fashion once per second. The resulting video display consists of 25 "pulses" per second corresponding to each frequency interception, with a complete scan of the frequency range each second. This pattern is recorded on magnetic tape for later playback and for analysis. Line-of-sight measurements, for calibration purposes, show the system response to be flat to within db.