This bridge connects M17 — a digital voice mode — to AllStar and EchoLink, two of the longest-running voice linking networks in amateur radio. It joins the family of explainers alongside XLX, URF, and mrefd, but it crosses a different kind of boundary: not from one digital mode to another, but from the digital-mode world to the analog-linking world. The good news is that M17 makes this crossing unusually painless.
AllStar and EchoLink are voice linking networks. Rather than carrying a tightly compressed over-the-air codec, they move audio between nodes as ordinary sound over the internet — the "analog side" of the hobby, where repeaters, simplex nodes, and computers link up and relay plain voice. M17, by contrast, is a digital mode: its audio is encoded with Codec2 for transmission over the air. A bridge sits between these two worlds so that an M17 user and an AllStar or EchoLink user end up in the same conversation.
The two worlds meet, as so often, in the form of plain digital audio carried over USRP — the same uncompressed audio-over-IP format that AllStar and the DVSwitch tools already use. The bridge's job is simply to convert M17 into that plain audio and hand it across.
The crossing point
On the M17 side, a small program (USRP2M17) converts between M17's Codec2 stream and plain USRP audio. On the other side, AllStar's node software (Asterisk / app_rpt) carries that audio into the AllStar network, and SVXLink carries it into EchoLink and the SVXReflector network. A transmission from an M17 user becomes plain audio, crosses the bridge, and arrives on AllStar or EchoLink as if it had come from any other node — and the same path works in reverse.
Here's the part that ties back to the other reflector explainers. Converting a digital voice stream into plain audio means running it through a vocoder — and for the proprietary codecs (D-Star's AMBE, or the AMBE+2 used by DMR and Fusion), that means buying hardware vocoder dongles. M17 avoids all of it.
Because M17 uses Codec2, an open-source codec, the conversion to and from plain audio is done entirely in software, on the bridge computer's own processor. No AMBE chips, no dongles, no licensing. Bridging M17 to AllStar or EchoLink costs nothing in special hardware — whereas bridging D-Star to the same networks would put you right back into buying vocoders. M17's openness, which made the mrefd reflector so simple, makes this bridge simple too.
AllStar (built on the Asterisk phone-switch software) and EchoLink are separate networks with separate histories, but from the bridge's point of view they're the same kind of thing: places where plain voice audio is linked between nodes. That's why a single design reaches both. The AllStar side is handled by the node's own Asterisk software speaking USRP; the EchoLink side is handled by SVXLink, which knows how to talk to the EchoLink network and can pass that same audio across the bridge. One crossing point, two destinations.
The M17-to-AllStar/EchoLink bridge is a translator between two halves of amateur radio that don't normally meet: the digital-mode world and the analog-linking world. It works by reducing M17 to plain audio over USRP and handing it to networks that already speak in plain audio. And because M17's codec is open-source software, the whole bridge runs without a scrap of special vocoding hardware — a small, quiet piece of software doing the work that proprietary modes would need expensive chips to accomplish.
The bridge described here rests on USRP2M17, the M17-to-USRP conversion program maintained in Tom Early's (N7TAE) nostar project — the same lineage behind the urfd and mrefd reflectors. A packaged implementation for linking has been published by Michael Webb (WG5EEK), whose USRP2M17-Selector adds a web interface and install tooling to run the bridge on AllStarLink and HamVOIP nodes, letting an operator select M17 reflectors and modules from a browser. This page explains the concept; their projects are where it lives as working software.
See: github.com/nostar/MMDVM_CM · github.com/mjwgeek/USRP2M17-Selector
A noncommercial hobby reference compiled by N6JET, gathered from public sources and shared freely for anyone interested in amateur digital voice.