How does sunspot activity affect Amateur Radio?

How does sunspot activity affect Amateur Radio?

Sunspots indicate solar activity which affects the ability of ionosphere to refract radio signals back to earth. More of solar activity means more of ultra violet rays will reach the earth’s atmosphere and increase ionization. From an HF transmitter, ground waves travel close to the ground while sky waves travel up and gets reflected back and forth from the ionosphere, extending the range of transmission. Number of sunspots wax and wane in a 11 year cycle. When the number of sunspots are low, propagation on HF bands will be very poor.

VHF/UHF transmission including Amateur Radio satellite operations may not be much affected by sunspot activity. Solar cycle 24 had a peak in 2013-14 and ebb in 2020. Now we are in solar cycle 25 which has already started rising better than predictions and we can expect good HF band conditions, with peak expected in 2024-25. Higher HF bands will be more affected by sunspot activity so that some bands may not open up during low sunspot activity.