Yaesu's DR-2X, DG-ID routing, and the mode that has the network half of roaming and nothing else. Working notes, v1.1, 10 September 2026.
C4FM is Yaesu's mode and Yaesu's alone. Its repeater does one thing no other mode's repeater does, deciding for itself whether an incoming signal is digital or FM. Its weakness is the opposite of NXDN's: it has the network half of roaming and none of the radio half.
The same four questions are asked of every mode, in the same order, so the seven parts stay comparable:
MMDVMHost plus a board. The gateway is YSFGateway, from G4KLX's YSFClients repo, which also ships a parrot. An important limit: MMDVM reaches YSF and FCS reflectors, not WIRES-X. WIRES-X is Yaesu's own closed network and needs Yaesu hardware. That is why the C4FM world is split three ways and needs bridges between them.
Yaesu, and only Yaesu. The DR-1X and the current DR-2X, a 144/430 dual band C4FM/FM repeater. Its signature feature is AMS, Automatic Mode Select: the repeater "automatically recognizes the signal as C4FM digital or conventional FM, and then re-transmits the signal using the preset communications mode." No other mode's repeater does that. The DR-2X also has MSRL, Multi-site Repeater Link, tying repeaters together over a LAN or WAN.
The repeater program is alive, and an article saying otherwise is an April Fools piece. A widely seen post dated 1 April 2025 claimed Yaesu had shut the program down. Yaesu's own application PDF for that year covers 12 March to 30 May 2025, a window that contains 1 April. The program has run in rolling two month windows ever since, the current one to 31 August 2026, and the DR-2X is in stock at Ham Radio Outlet at $1,749.95. The DR-1X is discontinued, filed by Yaesu under Legacy, though no source gives a date.
C4FM has no trunking. Not unused, not out of reach: the mode does not have it. C4FM is in the same group as D-STAR and M17 on this, so the question of why amateurs skip trunking never arises here. Part 7 covers that argument for DMR, NXDN and P25, which do have it.
| Mode | Channel bandwidth | Modulation | Bit rate |
|---|---|---|---|
| C4FM | 12.5 kHz, every mode | 4FSK | 9600 bps, 4800 symbols per second |
C4FM has no 25 kHz mode. Every Yaesu digital mode sits in 12.5 kHz at 9600 bps gross. "VW", Voice Wide, means a full rate vocoder consuming the whole payload, not a wider RF channel. The three modes divide the same 9600 bps differently: DN is 2450 voice plus 1150 FEC plus 3600 data, VW is 4400 voice plus 2800 FEC, and DW is 7200 bps with no FEC.
C4FM occupies the full 12.5 kHz and carries one conversation in it, so it is neither of the two efficiency camps: it does not narrow the RF the way D-STAR and NXDN do, and it does not divide the time the way DMR and P25 Phase 2 do. That is why a C4FM-locked multi-mode repeater carries one user.
Every mode has two different fields and they get confused constantly. An access field, which works like CTCSS and decides whether the repeater listens to you at all, and a routing field, which decides where your audio goes. C4FM is the clearest example of the split, because Yaesu gave the two halves nearly the same name.
| Mode | Access field | Routing field | Range |
|---|---|---|---|
| C4FM | RX DG-ID | TX DG-ID | 0 to 99 |
C4FM uses DG-ID, 0 to 99, and Yaesu splits it in two. TX DG-ID is routing and picks the room. RX DG-ID is access and filters what you hear. Set them independently and the radio transmits into one room while listening to everything.
That puts C4FM in the group of four modes that put routing in a number the user dials, alongside DMR's talkgroup, NXDN's destination ID and P25's talkgroup. D-STAR and M17 use a letter attached to a reflector name instead.
Roaming needs two halves: a network half, several sites linked so that being on any of them puts you in the same conversation, and a radio half, something the radio can measure plus logic to move by itself. C4FM has the network half and not the radio half, which makes it a clean illustration of why one half on its own does nothing.
The network half is real. MSRL and IMRS do link multiple C4FM sites over IP, so being on any of them puts you in the same conversation. That is the same half NXDN has.
The radio half is absent. The FT5D Advance Manual has no automatic node or repeater selection anywhere. The WIRES-X node search offers HISTORY or ACTIVITY lists and the operator picks. Repeater shift is a user-configured offset. Nothing switches by itself. No beacon, no vote scan, nothing in the radio that measures sites and moves.
Why having one half is not close to having roaming. C4FM's IP linking means you do not lose the conversation when you change sites. It does not mean the radio will change sites. Somebody still has to notice the signal is failing and turn the knob. Compare NXDN, which has both halves on commercial gear, and DMR, whose radio half is self-contained enough that the network half becomes optional.
C4FM is single channel, so a C4FM-locked repeater carries one user. Its MMDVMHost TXHang default is 4 seconds, listed in the ini as System Fusion. The mode hang timers and the reason the machine sends CW every ten minutes are in part 7.