Historic Sunspot Numbers

The sunspot cycle is of great interest to Radio Amateurs and other users of the HF spectrum.

The National Oceanic and Atmospheric Administration (NOAA) makes available the sunspot numbers for each month since 1945 on its website.

This historic sunspot data can be seen at

ftp://ftp.ngdc.noaa.gov/STP/SOLAR_DATA/
SUNSPOT_NUMBERS/AMERICAN_NUMBERS/RADAILY.PLT