Differences of Spread-F at Haikou and Huancayo

In this paper,the local time,seasonal and solar cycle variations of frequency spread-F at Haikou during years of maximum and minimum sunspots are studied.Comparing frequency spread-F at Haikou with frequency spread-F at Huancayo,it is found that differences of frequency spread-F at two stations are obvious.During maximum sunspot years,the occurrence of frequency spread-F is maximum between 2000-2100 LT at Haikou and at 0000 LT at Huancayo.During minimum sunspot years,the occurrence of frequency spread-F reaches a rather flat peak between 2300-0400 LT at Haikou and reaches a peak at 0000 LT at Huancayo.For seasonal variation,the occurrence of frequency spread-F at Haikou is maximum during equinoxes in maximum sunspot years and during summer solstice in minimum sunspot years,the occurrence of frequency spread-F at Huancayo is maximum during the winter solstice in both maximum and minimum sunspot years.