Kevin Grantham N5KRG
Depends on your radio or radios.
Generally speaking, you need to get a sound card connected to the radio to support a software modem in your computer. With a single sound card interface you can choose from packet (generally used for VHF and UHF as it’s not robust enough for HF), Winmor, Ardop or VARA.
How to get the sound card connected?
Some radios have a built-in sound card and a USB connection to your computer. Some have a six-pin mini-DIN connector and you can use any of a wide variety of sound cards and a suitable cable.
Some radios have proprietary connectors - if they are widely used radios there may be cable available, or you can make one.
Worst case is having to interface through the microphone and speaker connections.
So, that’s what you need. A Windows PC, some kind of a sound card, cable, and interface to the radio.