https://www.hamradiohats.com/shop/43750896/solar-cycles
Solar Cycles - Ham Radio Hats
solar cyclesham radiohats
https://www.sidc.be/SILSO/cyclesminmax
Solar Cycles Min/Max | SIDC
Dates of the minima and maxima of past solar cycles, with the corresponding sunspot number, based on the 13-month smoothed monthly sunspot number time series....
solar cyclesmin max