For a tech class ham digital modes can give you a real taste of the world of Ham radio, with the ability to contact ham operators around to world on VHF and UHF bands. This is accomplished through the use of the Internet as each of the below digital types operate by conecting their repeaters to the internet. More on this is eeper in my site.
D-Star
D–STAR is a digital voice and data protocol specification for amateur radio. The system was developed in the late 1990s by the Japan Amateur Radio League and uses minimum-shift keying in its packet-based standard.
DMR
Digital Mobile Radio is an open digital mobile radio standard defined in the European Telecommunications Standards Institute (ETSI) Standard and used in commercial products around the world.
Here is a gret Youtube video explaining DMR and how to program a radio or in technical terms “build a code plug”
NXDN
NXDN is an open standard Common Air Interface (CAI) technical protocol for mobile communications. It was developed jointly by Icom Incorporated and Kenwood Corporation.
P25 – Project 25
Project 25 (P25 or APCO-25) is a suite of standards for digital mobile radio communications designed for use by public safety organizations in North America. P25 radios are a direct replacement for analog UHF ( example FM) radios but add the ability to transfer data as well as voice, allowing for a more natural implementation of encryption or messaging.
C4FM or System Fusion
System Fusion is Yaesu’s implementation of Digital Amateur Radio, utilizing C4FM 4-level FSK Technology to transmit digital voice and data over the Amateur radio bands.