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.