FreeDV uses an audio codec as a software based modem to decode and encode the voice and text data from your computer. The data is encoded and then is transmitted over the HF radio using AF signals that can then in turn be decoded by the receiving station.
Ionospheric Propagation of Radio Waves in Action, How Do Ionized Layers Form to Enable Ionospheric Propagation of Radio Waves, the foundamental role of F layer, and the role of the other ionized layers
The Union of non-governmental organizations “The Ukrainian Amateur Radio League” (UNGO “UARL”) was founded in December of 2015. Currently, there are about 1500 members in the League, representing most regions and cities of Ukraine.