Sporadic-E propagation at frequencies around 70 MHz

Results are presented of observations extending over a decade of propagation by means of sporadic-E ionization at frequencies in the range 59 to 77 MHz. The seasonal, diurnal and longer term trends in the data are discussed. Cumulative distributions of event durations are presented for different groupings of the data. A limited study of possible polarization discrimination at these frequencies is also described. The results are discussed in terms of their potential use in spectrum planning at frequencies around 70 MHz.