Sun spots can be described as a prime motivator of radio communications. Every 11 years there is a change between cycles, we are currently beginning sunspot cycle 24 meaning that sunspots are beginning to appear on Old SOl. These sunspots make the high frequency bands particularly useful in that one is able to communicate farther. These same bands were almost useless as cycle 23 ended and cycle 24 began. The upper amateur radio bands 10 meters, 12 meters, 15 meters, and 17 meters were negatively affected by the lack of sunspots. As a side note you could also include the CB band of 11 meters as also being negatively affected by the low sunspot activity. The sunspots have a direct bearing on radio wave propagation (and the climate!1) and will be explained further in the section named Radio Propagation.
As mentioned before, the current sunspot cycle 24 is in the beginning stages. There are some excellent sites on the web dealing with sunspot activity. One very popular one is aptly named solarcycle24.com and has a huge amount of information on it concerning radio propagation and general and a great source for information on cycle 24. The link is to the web site is an easy to remember one: http://www.solarcycle24.com. This site is owned and operated by Kevin, VE3EN which is a Canadian amateur radio station.
Another great web site for sun spots as they apply to radio communications is that of N0NBH’s web site located at HAM QSL. His site is a major contributor to the radio community by providing the tools such as seen on the main page of this section. He also has an excellent explanation of the various conditions caused by sun spots. This very informative page is located at http://www.hamqsl.com/shortcut.html.
1 Sunspots and the climate changes have been tie together in that the weather changes pretty much follow the sunspots cycles. While Al Gore and the global warming theorists claim we are in meltdown stage it is scientifically proven that the weather too is cyclic.