EFFECTS OF EQUATORIAL SPREAD-F IRREGULARITIES ON C. W. TRANSMISSIONS

A study is made into the effects of spread-F conditions on continuous wave (c. w.) transmissions between Colombo and Waltair over a distance of about 1300 kilometers. It is shown that under suitable conditions increased fading rate of the received c. w. signals is a sufficient indication of spread F and gives a genuine index of its intensity. Pulse and c. w. methods are used simultaneously to study the time variations of spread-F intensity at separated points. The results indicate that the horizontal extent of spread-F occurrence in the N.–S. direction is greater than 650 km.The probability distributions of signal amplitudes in the c. w. fading records were closer to Rayleigh type under normal conditions than during spread-F conditions. It is suggested that the c. w. flutter fading is caused by the presence of spread-F irregularities in the appropriate zone of reflection in the F-region of the ionosphere.