Contests can bring very large numbers of stations to the high frequency radio bands in a short period of time. Because the amount of radio spectrum available is limited, this can result in significant competition for frequencies. Since stations in the Amateur Radio Service must share spectrum and are not assigned specific channels, no one station, contester or otherwise, has a "right" to use any particular frequency in a radio band. During big contest weekends, thousands of contesters take to the air causing much contention.