Amateur stations may not transmit in which of the following frequency segments if they are located in the contiguous 48 states and north of Line A?

Line A is an imaginary line within the United States that runs roughly parallel to the US-Canada border. Because radio waves do not stop at international borders, special frequency coordination rules exist to prevent interference between stations in both countries. In Canada, the 420 MHz to 430 MHz frequency segment is used by commercial and public safety land mobile stations. To prevent amateur radio operations in the northern US from interfering with these critical Canadian communications, the FCC prohibits US amateurs located in the contiguous 48 states and north of Line A from transmitting in the 420 MHz to 430 MHz segment. Other frequency segments, such as 440 MHz to 450 MHz or 222 MHz to 223 MHz, do not have this specific geographic restriction. If you operate near the Canadian border, it is crucial to verify your location relative to Line A before operating on the lower end of the 70-centimeter band.