Digital radio communications are audio sounds that are digitized. There are a variety of modes that may occupy less bandwidth, or perhaps allow communications with very weak signals or very noisy conditions.
From a presentation by W4TWK
Some Digital Ham Radio Resources
Digital, the waves of the future are here today.
Have you ever tried to distinguish various digital mode signals on a waterfall and
identify them when they are NOT PSK31. Here is some help.
Just click on the name of the modes along the left panel –
Each digital mode in the index links to a page with both audio and waterfall examples.
A great way to learn what’s out there.
More information on these modes:
Weak Signal Communication Software
WSJT, MP65, WSPR, and WSJT-X are open-source programs designed for weak-signal digital communication by amateur radio. Normal usage requires a standard SSB transceiver and a personal computer with sound card.
WSJT-X implements communication protocols or “modes” called FT8, JT4, JT9, JT65, QRA64, ISCAT, MSK144, and WSPR, as well as one called Echo for detecting and measuring your own radio signals reflected from the Moon. These modes were all designed for making reliable, confirmed QSOs under extreme weak-signal conditions.