Which frequency band is limited to mobile use in the U.S. amateur radio?

The correct answer is the 60-meter band, which is specifically limited to mobile use in the U.S. amateur radio context. The unique regulations surrounding this band mean that it is primarily intended for mobile operations, which align with certain designated frequencies and power limits.

The 60-meter band in the U.S. consists of specific channels that must be used according to strict rules, including maximum power output and restrictions that can affect how and when operators can use these frequencies. This is part of the broader framework aimed at harmonizing amateur radio operations while taking into account the interests of other services, particularly because these frequencies are close to those used by other licensed services.

The other bands listed, such as 30 meters, 20 meters, and 40 meters, have different regulations that allow for a variety of uses, including fixed and portable operations, in addition to mobile. This makes them more flexible in terms of operational modes compared to the highly regulated 60-meter band, underscoring the distinctiveness of the rules applied to each frequency range within the amateur radio spectrum.