Part of our Getting On The Air: Modes, Operations, and Making Contacts guide.
If you have started poking around digital modes like FT8, you have probably run into the name Digirig. It is a small, popular interface that sits between your radio and your computer. It is not the only device of its kind, but it has become a favorite for portable and home operators alike because it packs a lot into a very small package. Here is what it actually does, and why some radios need one while others do not.
What a Digirig is
A Digirig is a compact sound card and control interface in one. To run digital modes, your computer needs to do two separate jobs: it needs to exchange audio with the radio, and it needs to tell the radio when to transmit. A Digirig handles both.
Inside that little box are two main pieces:
- An audio interface (sound card). This carries receive audio from the radio into the computer so your software can decode it, and carries transmit audio from the computer back to the radio so it can send.
- A serial interface for control. This handles keying the transmitter (PTT) and, in many setups, CAT control so your software can read and change the radio’s frequency and mode.
It connects to your computer over a single USB cable and to your radio through cables specific to your radio’s connectors. That is really the whole idea: one small bridge that lets a computer and a radio talk to each other cleanly.
Why the audio path matters
You might wonder why you cannot just run a cable from your computer’s headphone jack to the radio. You can sometimes hack something together that way, but a dedicated interface like a Digirig gives you a clean, isolated audio path. Good interfaces keep the computer and radio electrically separated, which cuts down on hum, noise, and ground loops that can wreck your transmitted and received signal quality. It also keeps the two audio streams (to and from the radio) properly separated so your software behaves.
Why some radios need one and others do not
This is the part that confuses people, and it comes down to one question: does your radio already have a sound card and control interface built in?
Radios with a built-in USB interface do not need a Digirig. Many modern HF rigs have a USB port that presents itself to your computer as a sound card and a serial control port all at once. You plug in one USB cable and the computer sees everything it needs: audio in, audio out, PTT, and CAT. In that case the interface is already inside the radio, so an external one would just be redundant.
Radios without that built-in interface are where a Digirig earns its keep. Plenty of radios, including many older HF rigs, most handhelds, and a lot of mobile rigs, only give you analog audio connectors and a separate PTT or data jack. They have no way to hand audio to a computer over USB on their own. A Digirig supplies the missing sound card and keying, translating between the radio’s analog jacks and your computer’s USB port.
So the rule of thumb is simple. If your radio already shows up as a sound card when you plug it into your computer over USB, you likely do not need a Digirig. If it does not, and it only has audio and PTT jacks, then a Digirig (or a similar interface) is what bridges the gap.
Why the Digirig in particular is popular
There are other interfaces that do the same job, but the Digirig has a following for a few reasons. It is tiny and light, which makes it ideal for portable operating and go-kits. It supports a wide range of radios through radio-specific cables, so one small device can move between rigs. And it combines both the audio and the serial control functions in a single unit rather than needing separate boxes.
The bottom line: a Digirig is the translator that lets a computer and a radio work together for digital modes. Whether you need one depends entirely on whether your radio already has that translator built in.
See the Digirig in action with our setup walkthroughs for the FT-891 and the Xiegu G90, both of which need one to get on digital modes.