TelescopeMan describes a Signalink (sound card) used to connect an amateur radio to a computer. There is also another popular device called a Rigblaster.
Do you need to connect a desktop or laptop computer to a stereo using an RCA cable? Follow these simple steps to connect your computer to your stereo system.
There are two parts to the interface between your computer and the radio. The first half is a simple connection from a external speaker jack on your radio to the microphone input to your computer.
This is the official RR Live Audio suggested method to connecting your radio and computer for a reliable and good quality audio feed. There may be other connection methods but some of them do not work reliably and may deliver poor results over time.