The paper begins with a description of an experimental earth station especially designed for moon-reflection communication purposes. This is followed by a description of the experimental results of the characteristics of the moon-reflected signals obtained at an operating frequency in the lowerXband. The received signal envelope was found to fade within wide limits and the fading rate was dependent on the libration rate of the moon. The maximum rms frequency in the frequency spectrum of the envelope was estimated to be on the order of 60 Hz, giving an approximate measure of the frequency spreading due to the libration of the moon. The statistical analysis of the echo envelope has also been carried out and it was found to follow the Rayleigh distribution. Our results imply that atXband a discrete coherent reflector does not seem to be present and consequently, the moon may be regarded as a reflector composed of a large number of scatterers distributed over its surface.

A new spread spectrum technique using band-limited Gaussian noise for transmission and incoherent detection at the receiver has been discussed. The proposed system called noise band shift keying (NBSK) may be considered as a modified form of the frequency-shift keying (FSK) system. In the NBSK system nonoverlapping bandlimited noise is transmitted instead of pure tones as in the FSK system and the center frequency of the noise is chosen on the basis of the binary data signal. For this system, an expression for the probability of error has been derived and it has been shown that its performance under nonfading channel conditions is identical to that of the FSK system with frequency diversity under Rayleigh fading conditions. Compared to the conventional spread spectrum systems, the proposed method is considerably more simple to implement and is attractive where adequate bandwidth is available.