What term describes an amateur station that is transmitting and receiving on the same frequency?

The term that describes an amateur station transmitting and receiving on the same frequency is known as simplex. In a simplex communication system, both the transmitter and receiver operate on the same channel, which means that at any given time, one party sends a signal, while the other listens. This is a common mode of operation for amateur radio because it simplifies the communication process and can be very effective, especially for informal conversations.

The other terms refer to different modes of communication. For example, full duplex refers to the ability to transmit and receive simultaneously on different frequencies, which requires more complex equipment. Diplex involves the ability to send two different signals over the same medium but usually on different frequencies, and multiplexing allows for multiple signals to be sent over a single channel but requires separating them according to time or frequency. In contrast, simplex is the straightforward method utilized in amateur radio communications where voice or data is sent one way at a time on a shared frequency.