Digital

There are many digital modes available for amateur radio, including keyboard-to-keyboard modes such as RTTY (radioteletype), PSK31, and JS8, file transfer modes such as MT63, partially-automated "weak signal" modes such as FT8, networking systems such as packet radio and High-Speed Multimedia (HSMM, Wi-Fi mesh networks using ham radio), and digital voice modes such as FreeDV and DMR. Slow-scan Television (SSTV) is also often included in the digital modes, despite the fact that most SSTV modes are technically analog, because the use of computers for encoding and decoding SSTV is now almost universal.

Keyboard-to-keyboard modes

RTTY, the first digital mode, is a keyboard-to-keyboard mode. RTTY was developed before computers were widely available; originally, special electric typewriters were connected to hardware radio modems. However, the use of these systems is now rare; the majority of RTTY operators use computer software that modulates and demodulates the tones using the computer sound card. PSK31 operators virtually always use a computer for modulation and demodulation. PSK31 has several advantages over RTTY, including improved reliability and support for lowercase letters. JS8 is even more reliable than PSK31, although it is significantly slower and, like RTTY, does not support lowercase letters. JS8 uses much of the same technology as FT8.

Weak-signal modes

Weak-signal modes, such as FT8, use mostly automated exchanges to improve performance with weak-signals. They tend to be quite slow; FT8 takes 15 seconds to send a 13 character message. JS8 is somewhat unusual; it uses the weak-signal technology of FT8 for keyboard-to-keyboard communication.