C4FM – FDMA (Frequency Division Multiple Access)

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.

The operating modes for System Fusion are as follows.

  • V/D (Digital Narrow) – Voice+Digital or “V/D” mode
    Voice FR (VW) Mode – Utilizes all available bandwidth for high-fidelity voice operation, providing the most crystal clear of voice communications.
  • Highspeed Data
    Transfer data such as images or text messages at full rate with speeds up to 9600 Bits-per-second
  • Analog FM Mode
    Maintains backwards compatibility with existing Analog FM Equipment, allowing a wide range of users to experiment with System Fusion Digital.
HH Yaesu FT2D

Mostly referred to as Fusion, it is the newest digital radio mode.  It was designed by Yaesu and is not an open standard.  Yaesu is the only manufacturer of radios for this mode.  Yaesu repeaters are true multi-mode capable and can replace an existing analog repeater while still providing digital capabilities.  It can also transcode an incoming digital signal to analog or an incoming analog to digital or it can transmit what it receives, no matter if it is digital or analogue.

Fusion radios are capable of Normal FM, and the Yaesu Digital C4FM. In basic operation, you can use some repeaters in either mode. It is configured in what is known as Auto-Auto. If it receives FM it will go out FM, If it receives digital it will go out digital. The systems need 200ms or so to establish the connections between repeaters, many of them also have separate voice and command pipes, this means that the unkey command can arrive at the remote repeater before the last of the voice.

~ C4FM ~

The most attractive advantage of digital communication is the ability to transfer large amounts of data. The 12.5 kHz channel spacing in using the C4FM FDMA digital modulation mode allows high-speed data communication with reliable voice communication and strong error correction performance. C4FM FDMA offers a 9.6 kbps data transfer rate speed. It differs significantly from existing digital radio systems and expands the possibilities for interesting amateur radio activities in the future.

The C4FM / FDMA technology provides three digital modes and an analogue mode (FM)

V/D-mode Voice and data communication in the same time frame.


This mode allows voice data with GPS position data and the ID data to be sent in the same time frame. In addition, transmitting voice data with strong error correction data, this mode contributes to the stabilization of digital communication.

Voice/FR mode uses the full data rate of capacity for voice data.


This mode allows for clear high-quality voice data transmission.

This mode is the basic mode of C4FM FDMA Digital HAM radio system.

Analogue FM mode


Analogue FM mode is the same as the current FM mode used by all.

Yaesu incorporated a suite of features within the System Fusion product line that are designed specifically for Amateur Radio Use. These features allow the operator to transmit high-quality digital voice simultaneously along with Digital Data, and a High Rate (Data FR Mode) dedicated Digital Data mode that provides a method of transmitting Images, Text message and Telemetry Data at a high rate of speed.


Unlike its commercial counterpart, System Fusion is an amateur friendly digital operating mode, straying away from some of the design considerations that make commercial solutions less appealing and more difficult for Amateur Radio Operators, providing a simpler interface and features that meet the demands and needs of the Amateur enthusiast specifically. Below you will find more information on this marvellous new technology, and how it can meet every operators demand and needs for a clear and simple digital experience.

Source: Yaesu and on0dp

~ WiRES-X ~

WIRES-X (Wide-Coverage Internet Repeater Enhancement System) is a comprehensive and easy-to-use system for linking repeaters and/or home stations together, using Internet voice technology. You can talk to friends, or make new ones, around the world. More information on WiRES-X can be found by visiting the WiRES-X Information Page

WIRES (Wide-coverage Internet Repeater Enhancement System) is an Internet communication system which expands the range of amateur radio communication. For WIRES-X, an amateur node station connecting to the Internet is used as the access point and connects the wireless communication to the Internet. Users’ stations can communicate with other amateur stations all over the world using a node within the radio wave range.

Functional diagram of the WIRES-X communications system
Functional diagram of the WIRES-X communications system

WIRES-X supports the C4FM digital and the clear and crisp voice technology enables high sound quality. By repeating C4FM digital data as it is via the Internet, users can enjoy clear voice communications even if they are thousands of miles away from each other. Utilizing the digital communication, the WIRES-X operation is simple, easy and user-friendly.

WIRES-X automatically connects to nodes and rooms via the Internet. No more need to verify connection IDs or transmit cumbersome DTMF connection codes. Information about nodes and rooms is exchanged via C4FM Digital signaling. Thanks to automatic reconnection to the previous contact, all you need to do is press PTT and start talking.Easily search for new nodes and rooms, and initiate communication promptly when you find an ID that captures your interest.


WIRES-X of course also supports traditional analog FM users. Not only can analog FM stations have a QSO with each other, WIRES-X also permits C4FM Digital stations to communicate with analog FM stations. WIRES-X is an FM friendly digital solution, because Amateur Radio should always allow operators to communicate freely all over the globe.