Under which of the following circumstances are one-way transmissions by an amateur station prohibited?

• A. Emergency communications
• B. Broadcasting
• C. Repeating messages
• D. Calling CQ

Answer: (B)

One-way transmissions by an amateur station are prohibited primarily in the context of broadcasting. Broadcasting entails sending a signal to a broad audience without expecting a direct communication back from any individuals, which is contrary to the foundational principles of amateur radio. Amateur radio is designed for two-way communications, allowing operators to engage in conversations and exchange information with each other.

In emergency communications, one-way transmissions can be essential for conveying urgent information, and repeating messages serves the purpose of ensuring that the information is accurately conveyed and received. Calling CQ is also a part of interactive communication where one operator invites others to respond. Therefore, the nature of amateur radio requires that communications be primarily two-way, making broadcasting, which lacks this interactivity, the only circumstance among the choices provided where one-way transmissions are not permitted.