In a line-of-sight link with specular reflection, supposing fixed the distance between transmitter and receiver as well as the antennas height, the received field oscillates according to the random variation of the effective earth radius. By using computer simulation, this work intends to discuss the application of dual space diversity reception to this problem. In order tomake the simulation, it has been necessary to fix the statistical distribuition of the refractive index gradient. Experimental results have shown this gradient satisfies approximately a normal distribution. We can then achieve the statistical behaviour of the effective-earth radius. This distribution is well know in temperate regions. Nevertheless, only few observations are available for tropical and equatorial regions. So, included in this work is a discussion about the effects of mean and deviation variation of the gradient distribution upon the results. The system behaviour was analised in the following way. First of all, the transmitting and receiving antenna was supposed fixed and the other one gradually changed in position, in other one gradually changed in position, in order to obtain the optimun spacing. The criterion used in the design of the first two antennas (transmitting and fixed receiving) was to keep a 6/10 path clearance of the first Fresnel zone radius for the minimum value of K. This procedure leads to the certainty the received field will be in the interference region for more than 99,9% in time. According to the statistical distribution of the refractive index gradient there were generated ten thousand.