What’s the difference between simplex and duplex operation?

Single-Transceiver Operation (Simpex)

In simplex operation, a single transceiver handles both transmit and receive functions. This is a common setup for ham radio operators who use a single radio for both sending and receiving messages. Simpex operation is typically used for simplex communication, where one station transmits while the other station receives, without simultaneous transmission and reception. However, simplex communication can lead to delays and may not be suitable for real-time communication.

Duplex Communication Requirements

For duplex communication, separate transceivers are required for transmit and receive operations. The transmit transceiver sends the message, while the receive transceiver receives the message from the other station. This setup allows for simultaneous transmission and reception, which is essential for real-time communication and efficient data exchange. In a typical duplex setup, the transmit and receive frequencies are separated by a frequency offset, usually 500-2000 Hz, to avoid mutual interference.

Ham Radio Duplex Operation Examples

In ham radio, duplex operation is commonly used in repeater systems, where a single transceiver is used for transmit and receive operations, but with a frequency shift between the two directions. For example, in a 146 MHz repeater system, the transmit frequency might be 146.500 MHz, and the receive frequency might be 146.550 MHz, with a 500 Hz frequency offset. This allows for simultaneous transmission and reception, enabling real-time communication between stations.