Variations of radio noise parameters at a tropical station

Abstract

The results of a 4-year (1958–1961) period of measurement of atmospheric radio noise at chosen frequencies in the range 10 kc/s–20 Mc/s at Ibadan (7°26′N, 3°54′E) in a tropical area have been analyzed to confirm the systematic and random variations of noise parameters in the tropics. These variations are discussed and it is shown that the diurnal, monthly and seasonal variations of atmospheric noise levels are determined mainly by local thunderstorm activity and ionospheric absorption. The noise levels also show marked decrease with rise in frequency and are generally highest during the spring months. Atmospheric noise levels averaged over yearly periods tend to be reduced in the kilocycles range and increased in the megacycles range by enhanced sunspot activity. Abnormal variations which wore observed during the period, have been related to a low-altitude nuclear detonation in the Sahara Desert.