Güvenli açılış
PTT açılışta donanımsal olarak kapalı; yeniden başlayan uygulama önceki yayını sürdürmez.
Running radio sites over the internet from one panel
A self-hosted EchoLink alternative built from Raspberry Pi gateways, a low-latency media relay and a Laravel panel.
- Industry
- Telecommunications
- Duration
- 2 months
- Technologies
- Php-LaravelPythonGoMySQLRedisDockerWireGuardRaspberry Pi
4
Independent system planes
20 ms
Opus audio frame
T01–T16
Defined acceptance tests
The problem: scattered sites, invisible faults
The usual way to link analog radio sites is to rely on a third-party internet linking service — leaving connection policies, monitoring data and device management outside the operator's control.
The hard part is in the field, not in software: RF interference, internet outages, wrong audio levels or a stuck PTT are not fixed by a new app. The goal was to make these problems measurable and diagnosable remotely.
- Add a new site without writing code
- Split repeaters into independent talk groups, or join them under control
- See dropouts, silent audio, clipping and stuck PTT remotely
- Version, roll out and roll back configuration safely
Mimari
Four planes, clear responsibilities
Audio never passes through the web app, its queues or its database. Even if the panel goes down, established talks continue until their grants expire.
-
Field At every site
-
Radio Handheld or mobile, analog FM
-
Audio / PTT interface Level matching, isolation, PTT driver
-
Raspberry Pi gateway Go agent: audio, Opus, COS/VOX, state machine
WireGuard · RTP/Opus -
-
Media plane Server
-
Media relay Go; one talker per group
-
Sessions & grants Verified identity, time-limited grants
Events · grants -
-
Control plane Server
-
Control panel Organizations, inventory, groups
-
Live view Real-time status and talk history
-
Versioned config Saved and applied tracked separately
Bridge contract -
-
Extensions Separate nodes
-
DMR bridge Link to a network talkgroup
-
Voice assistant Node that answers by callsign
-
APRS iGate Receive only
-
Field gateway
A small computer at every site, strict rules
Each site has a Raspberry Pi, a full-duplex USB sound card and a radio interface. The Go agent on the Pi captures audio, encodes it with Opus, detects an open receiver from the COS signal or audio level, and drives PTT.
The agent runs an explicit state machine: PTT is held off in hardware at boot, and a restarted application never resumes a previous transmission. If the link to the server is lost, the safe shutdown happens locally; an independent watchdog also limits continuous transmit time.
Connections are opened from the site outwards, so no port forwarding is needed at the site.
Konuşma akışı
How one transmission travels between sites
Only one source can talk in a group at a time. The first valid request wins; talks are never queued and played out later.
-
1 · Receive Site A
-
User talks Radio A, analog FM
-
Receiver opens COS or audio detection; a short pre-buffer keeps the first syllable
Floor request -
-
2 · Floor Relay
-
Request evaluated First valid request wins
-
Others get busy No queue; the user tries again
Opus · 20 ms -
-
3 · Distribution Relay
-
Authorized targets only Gateways in the group
-
Stale packets dropped Session and sequence checks
RTP/UDP · WireGuard -
-
4 · Transmit Site B
-
Is the channel clear? No transmit while receiving locally
-
PTT and audio PTT released at the end
-
Ses profili
Audio transport tuned for speech
| Parameter | Starting value | Why |
|---|---|---|
| Codec | Opus, mono | Tunable compression and loss tolerance for speech |
| Encoder input | 16 kHz, 16-bit | Resampled with filtering if the card runs at another rate |
| Bitrate | 20 kbit/s (16–24) | Quality vs. bandwidth compared by measurement |
| Frame size | 20 ms (≈50 packets/s) | Balance between latency and efficiency |
| Jitter buffer | 40–80 ms | Upper bound and late-packet drop policy |
| Packet loss concealment | On | Softens the effect of lost frames |
| DTX | Off in the first release | Keeps silence, loss and end of talk distinguishable |
Starting values; tuned per site by measurement.
Saha donanımı
Hardware per site
| Part | Role | Selection criteria |
|---|---|---|
| Core | ||
| Raspberry Pi | Runs the agent | Small model for the prototype; Ethernet and measured load decide in the field |
| USB sound card | Audio capture and playback | Stable on Linux over long runs, separate in/out |
| Analog FM radio | Transmit and receive | External mic, speaker and PTT access |
| Interface | ||
| RX/TX matching board | Levels and isolation | Attenuation, DC blocking |
| PTT driver | Keys the radio | Isolates the Pi from the radio's electrical interface |
| COS input | Is the receiver open? | If the radio exposes it; otherwise audio-based detection |
| Field release | ||
| Independent watchdog | Cuts transmit on a hang | Runs independently of the application |
| Power, enclosure, ferrites | Uptime and interference | Pi and radio power budgeted separately |
Reliability is part of the design
A fault in the field must never leave a radio stuck on air, and an outage at the server must not drop talks.
Bağımsız watchdog
Uygulama kilitlenirse ya da yayın süresi aşılırsa telsizi yayından çeker.
Cihaz kimliği
Her geçidin kendi anahtarı vardır; cihazın beyanına değil doğrulanmış kimliğe güvenilir.
Sürümlü ayarlar
Panelde kaydedilen ile sahada uygulanan ayar ayrı izlenir; hatalı ayar geri alınır.
Panelden bağımsız ses
Ses yolu ayrı servistedir; panel ya da arka plan işleri durduğunda konuşmalar sürer.
Geri besleme koruması
Her RF alanında tek yayın geçidi; aynı frekansı duyan noktalar sesi geri döndüremez.
Extension nodes
New capabilities without touching the core
New capabilities are not built into the core; they are added as separate nodes that use the same talk-group contract.
The DMR bridge links a network talkgroup to the platform. The voice assistant node answers time, weather and propagation questions in amateur radio style when called by callsign. The APRS iGate node is receive-only and forwards position packets to the internet.
Each extension was designed through its own architecture decision record and runs as its own service.
Lessons from the field
The field test surfaced details the lab simulation could not. A talk session that stayed open long after the radio fell silent was traced with a field recording: a small DC offset at the sound card input made silence look like audio and kept VOX open. The agent now filters DC on the capture path; on the same recording VOX closes in 1.8 seconds.
Busy repeater traffic also reshaped the alarm logic: back-to-back short transmissions could falsely trigger the "stuck transmitter" alarm. The alarm now uses the PTT time measured by the agent and only fires after more than 70 seconds of continuous transmit.
Timeline
-
October 2026
Scope and architecture decisions
Project specification, acceptance tests (T01–T16) and the first architecture decision records.
-
October 2026
Panel, relay and field agent
Control panel, Go media relay and Pi agent; end-to-end lab simulation with two virtual gateways.
-
October 2026
Live view and hardware guide
Real-time status and talk history; a step-by-step hardware wiring guide inside the panel.
-
October 2026
Extension nodes
DMR bridge, voice assistant and APRS iGate nodes.
-
October 2026
Field test
Tried with real radios in two separate analog FM cells. Field recordings directly shaped the agent's audio and alarm settings.
Technology
Technologies
Backend
Php-Laravel
Python
Go
Database
MySQL
Redis
DevOps
Docker
WireGuard
Other
Raspberry Pi
Planning a system that runs in the field?
We design the hardware, real-time software and control panel together.
Request a quote
Call us+90 850 840 25 29
Have a similar project?
Share your needs and we will design and deliver a tailored solution.