The Computer / Transceiver Interface

I’m not sure of the percentage, but I suspect that most, if not almost all, ham radio stations of 2018 include a computer, usually connected to their transceiver. A computer is mainly used for:

  • Running logging, mapping, propagation, contenting, design, programming, and other sorts of software that may or may not require direct connection to the radio.
  • Running rig control software – to monitor frequency, change modes, control transmission, and perhaps rotor or antenna control.
  • Running SDR software.
  • Running digital mode software, which included encoding and decoding via the audio interface, and usually includes some basic rig control.

This short article will discuss the computer / transceiver interface, including rig control and the audio interface.


CAT Rig Control

For modern ham transceivers (1980s and later) with microprocessor control (frequency, modes, etc.), a protocol called CAT (for Computer Aided Tuning or Computer Aided Transceiver – it is unclear which is the real term) allows a computer to remotely control various aspects of a transceiver. CAT can control frequency, transmit, modes, and other controls found on typical transceivers.

Until fairly recently (perhaps 2010), the CAT connection to the computer was via an RS-232 serial interface cable. Sometimes a simple RS-232 cable will work, but not all radios have used standard RS-232 voltages, and level conversion hardware is often required.

There are a number of commercially available boxes that can connect computers to radios, often including the audio connection.

More recently it has become more and more difficult to find a Windows based PC that has an RS-232 port. There are also commercial boxes that will convert the RS-232 signals to a USB (Universal Serial Bus) connection. These conversion boxes require a PC software driver so that the PC rig control software will think it is still talking to an RS-232 port.

There are quite a few transceiver to computer interface boxes available – make a Google search to find various models. Currently, I think one of the best price for features value is with the SignaLink USB box from

SignaLink from

The most modern transceivers will skip the RS-232 connector completely, and provide a direct USB connection from transceiver to computer, along with appropriate drivers.

Rig control via CAT usually uses a different set of commands for each brand of radio. Modern software that uses rig control provide settings that can work with a very large number of radios. Some will even interface to the rig via software protocols with other software. For example, WSJT-X can communicate directly to a radio, or via the CAT interface of Ham Radio Deluxe or DXLab Suite.

Audio Interface

If you also want to use digital modes such as PSK31 or FT8, you also need to connect your computer to the audio input and output of your transceiver. Formerly, the audio connections were made directly from the computer’s audio out and in jacks to the radio’s jacks. This works, but is touchy when setting audio levels, and can make it difficult to also get the normal audio output for computer sounds or music.

The current boxes such as the SignaLink and direct USB connection include independent audio pathways, and make the whole process easier.


Modern Ham Rigs can be controlled via a CAT interface. Connecting computer to the radio can be done directly via a computer USB cable, or via one of several interface boxes. The various ham apps that provide rig control provide settings to work with different models and brands of radios.