C4FM & System Fusion
System Fusion is a digital communication system for amateur radio developed by Yaesu, designed to integrate digital voice, FM analog voice, and data in a simple and flexible way.
Main features:
FM Analog Compatibility:
One of System Fusion's strengths is its backward compatibility with analog FM: repeaters and Yaesu radios in Fusion mode can switch automatically between digital and analog (using the 'AMS' – Automatic Mode Select feature).
C4FM Digital Mode:
It uses the C4FM (4-level FSK) digital codec, a digital modulation offering high audio quality and low latency. It is not compatible with other digital standards like DMR or D-STAR, but it is simpler to configure.
Data and Image Transmission:
It supports the transmission of images, text messages, GPS, and other digital information.
WIRES-X (Wide-coverage Internet Repeater Enhancement System):
A system that allows repeaters and compatible radios to connect via the internet to other nodes/repeaters worldwide. Each node can be connected to a thematic or regional "room", similar to DMR "talkgroups" or D-STAR reflector modules.
System Fusion uses four transmission modes, all within 12.5 kHz, but with different bitrate allocations:
| C4FM Mode | Voice | Data | Description |
|---|---|---|---|
| V/D Mode (Voice/Data) | 3600 bps | 5400 bps | Used for voice + data like GPS, ID, etc. |
| Data FR Mode (Full Rate) | – | 9600 bps | Data only (e.g. images, files) |
| Voice FR Mode (Full Rate) | 7200 bps | 2400 bps | Voice only, highest audio quality |
| Analog FM | N/A | N/A | Compatibility with classic analog FM |
Wires-X is a proprietary Yaesu system; another open-source alternative exists, called YSF, which performs the same functions (and is in fact what is used, for example, by hotspots):
| Feature | YSF (Yaesu System Fusion Network) | WIRES-X (Wide-Coverage Internet Repeater) |
|---|---|---|
| Developer | Open-source community (e.g. MMDVM, Pi-Star, YSFReflector) | Yaesu (proprietary) |
| Protocols | YSF, MMDVMHost, open source | Yaesu proprietary, closed |
| System type | Server-based reflector (like DMR BrandMeister) | Node-based (direct connection between Yaesu nodes via the internet) |
| Required hardware | Can run on open hotspots (Pi-Star, etc.) | Requires original Yaesu hardware (e.g. HRI-200, DR-2X) |
| Accessibility | Open, no registration, free software | Closed, requires registration with Yaesu and HRI-200 |
| Audio quality | Good, depends on node configuration | Excellent (native voice + data, deep integration with Yaesu radios) |
| Compatibility | Can be used on MMDVM, OpenSpot hotspots, etc. | Certified Yaesu radios and repeaters only |
| Room / Reflector | Reflector (e.g. YSF23456 - Italy), similar to TGs | WIRES-X Room, registered and managed by Yaesu |
| Cross-linking | Broad (YSF ↔ DMR ↔ NXDN ↔ P25 ↔ D-STAR with bridges) | Limited to the WIRES-X ecosystem |
| Configurability | High, scriptable, customizable | Limited, managed via Yaesu software |
How do reflectors work? And DG-IDs?
Imagine we are in a city (the Internet) where there are various residential buildings; some will have more rooms, some fewer, some only one.
When we connect to a radio repeater belonging to the YSF network and press the PTT, we will transmit in the room that the repeater is connected to.
Is it possible to know which building we are in? Yes: using the device's Wires-X function, we can switch to digital and query the repeater (or hotspot) to understand which reflector we are connected to (it is literally written there). That said, through the Search Direct (or direct input) function, we can change "buildings". Fine, but where is the list of available buildings? The list is dynamic: a site that lists them all is WPSD: choosing the YSF reflector makes the repeater (or hotspot) connect to that building. And now comes the beautiful part. Initially, each building had only one room: meaning that choosing, for example, YSF-39055, anyone who accessed it would have been able to communicate with the other bystanders. However, with the creation of multi-stream reflectors, this is not necessarily true: upon first entry, in fact, you are placed in a default group (groups can go from 0 to 99); which group it is is decided by the reflector administrator. After that, you can move around within the "rooms" of the building. The rooms are represented by DG-IDs, which can be set when you are not in Wires-X mode.
Let's see a practical example: we want to talk in room 51 of reflector YSF-39055 (51 was decided to be, on that specific reflector, the Tuscan thematic room). What do we need to do?
- Switch to Wires-X mode.
- Search and connect to reflector YSF-39055.
- Exit Wires-X mode.
- Set TX DG-ID = 51 (only transmit TX DG-ID=51; receive must remain RX DG-ID=00).
- Key the PTT.
- From the next PTT on, you are speaking in the thematic room.
How many reflectors can you choose from? Hundreds.
Which ones have only one room and which ones use DG-IDs? I wouldn't know, they change, there is no rule. But is DG-ID 51 always Tuscany? Sure, keep dreaming. There is no convention whatsoever. On my reflector 51 could be Tuscany, on yours Bangladesh, on your friend's they might be talking about politics.
Although, in my opinion, it is more entropic than other systems (certainly more than DMR on BrandMeister), it offers superior audio quality compared to other digital protocols. Unfortunately, the Yaesu handheld radios of which I am a proud owner (FT-70D, FT-5D) are not exactly the best in terms of battery life, and the system does not allow D-STAR-style Call Routing calls, making it less preferable (in my eyes) compared to the latter.
Discussion & SupportDiscussion and support channel. To discuss configurations or other topics, join us on fluxer.dreadful.work.
:: Kryfo Direct Chat ::