Graywolf APRS application

Graywolf is an open-source modern APRS station written by Chris Snell, NW5W. Unlike a typical “APRS client,” Graywolf bundles the entire stack — software modem, digipeater, iGate, and web-based user interface — into a single binary. It runs on Linux (Debian/Ubuntu, RHEL, Arch), Windows, and on ARM hardware including the Raspberry Pi.

Why it caught members’ attention

Two things stood out when we looked at Graywolf during the April monthly meeting:

1. Performance. The Rust-based AFSK demodulator outperforms Direwolf’s best mode on every track of the WA8LMF TNC test CD — while using roughly 5% of a Raspberry Pi 5. For a deployable digipeater/iGate, that’s a meaningful margin: more decoded packets in marginal-signal conditions, less power draw, less heat.

2. Self-contained. A single binary plus a SQLite config means a member can spin up a complete APRS station — modem, digipeater, iGate, web UI — without assembling the half-dozen separate tools a traditional Linux APRS setup tends to require. That’s a real advantage for portable kits and one-off drill deployments.

Feature highlights

• Software modem — native Rust DSP. Supports AFSK 1200 (Bell 202), 9600-baud G3RUH, PSK, plus FX.25 and IL2P forward error correction. SDR input is supported alongside conventional sound-card input.
• PTT — serial RTS/DTR, CM108 USB HID GPIO (AIOC, homebrew sound cards), Linux GPIO (Raspberry Pi, BeagleBone), and Hamlib rigctld.
• Digipeater — WIDEn-N path handling, preset-driven configuration (fill-in, wide-area), duplicate suppression, per-path filtering.
• iGate — bidirectional APRS-IS gating with configurable filters.
• Live map + messaging — real-time station map with trails, weather overlays, and SMS-style APRS messaging with delivery status.
• TNC interfaces — speaks KISS (serial and TCP) and AGWPE TCP, so it can act as the radio side for other packet applications.
• Observability — Prometheus metrics, SQLite packet logs, and a live packet stream in the web UI.

How it relates to what DeKalb ARES is already doing

We currently run W4BOC-1 as our digipeater/iGate on Stone Mountain on conventional hardware. Graywolf is interesting as a possible software platform for member-built portable APRS stations during drills and activations — for example, an operator showing up to a fire station with a Raspberry Pi running Graywolf could provide fill-in coverage in areas not well-served by a single mountaintop site. It’s also a teaching tool: the web UI makes packet decoding visible, which is useful for new members trying to understand what APRS actually looks like on the air.

Resources

• Source code, releases, and issues: github.com/chrissnell/graywolf
• Handbook (install + config + REST API): chrissnell.com/software/graywolf
• Known-working hardware configurations: chrissnell.com/software/graywolf/configurations.html
• Community Discord: discord.gg/TYcHzgWf