THE OPTIMUM RANGE FOR HF COMMUNICATION.
STANFORD UNIV CA STANFORD ELECTRONICS LABS
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A study of HF communication indicates that for best signal-to-noise ratio there exists an optimum distance between transmitter and receiver, assuming a system which always operates on the frequency that maximizes the received signal-to-noise ratio. Computations were made assuming four different spherical ionospheres corresponding to summer and winter, noon and midnight, at a temperature latitude. A broadband vertically steerable antenna of fixed area was assumed at one end of the path and isotrope at the other. The calculations were performed with the aid of a digital computer, taking into account such effects as ray focusing and the variations of noise, absorption, and antenna gain with frequency. The results show that the signal-to-noise ratio increases with the range by amounts varying from 20 to 30 db, between roughly 500 and 3000 km. At longer ranges, the signal-to-noise ratio decreases due to the decrease in antenna gain for low angles.
- Radio Communications