System Fusion (C4FM) digital voice
Yaesu's digital voice system for hams.
What does it sound like?
A harsh, buzzing digital sound.
Who uses it?
Amateur radio operators.
Where and when can I hear it?
Ham VHF/UHF repeaters.
The science
System Fusion uses C4FM, four-level frequency shift keying, in a 12.5 kHz channel: the carrier steps among four frequencies, each standing for a pair of bits. Speech is compressed with a digital vocoder. Yaesu offers a narrow voice-plus-data mode (DN) that sends voice and data such as GPS position together, a full-rate voice mode (VW) that spends the whole channel on higher-quality voice, a data mode reaching 9,600 bits per second for pictures and text, and ordinary analog FM.
Why use it?
Automatic Mode Select lets a Fusion radio recognize whether an incoming signal is digital or analog FM and switch to match. Built-in position data, text and picture messaging add features FM cannot, and Yaesu's WIRES-X system links repeaters and stations over the internet.
Lore
Yaesu introduced System Fusion in 2013.
Easily confused with
- D-STAR digital voice: D-STAR sounds smoother (GMSK)
- DMR digital voice: DMR has a pulsing edge