See It in Action
Adaptive UI from 2.4" rugged PoC radios to large-screen smartphones.
Full DPAD navigation — 100% usable on non-touchscreen devices.
Features
ETSI ACELP Codec
Full ETSI-compliant ACELP voice codec at 7.2 kbps. 100% compatible with commercial TETRA terminals on both RX and TX. Aligned to ETSI EN 300 395-4, EN 300 395-2, and ETSI ES 202 050 audio normalization standards. Voice quality measured against ITU-T P.862 (PESQ) and ITU-T P.50 reference signals with continuous validation throughout the development cycle.
ETSI EN 300 395-4Native DSP Engine
Bare-metal C++ audio pipeline with ARM NEON SIMD vectorization. Multi-stage signal conditioning: parametric equalization, adaptive automatic gain control, peak limiting, and spectral noise reduction. Zero-copy processing with sub-millisecond per-frame execution on Cortex-A55 and above.
C++ / NEON SIMDLow Latency PTT
End-to-end TX latency under 40ms from microphone to network. Microphone activated exclusively during push-to-talk for battery efficiency and privacy. Native hardware PTT button and rotary channel dial support for the Hytera P50 family. External PTT accessories supported via hamlink.app/ptt integrations.
< 40ms TXSpectral Noise Reduction
Frequency-domain noise suppression with weighted overlap-add synthesis. Adaptive per-bin estimation tracks ambient noise floor in real time, preserving speech formants while attenuating broadband interference before ACELP encoding.
FFT-based NRBrew Protocol
WebSocket TLS (port 443) TETRA Homebrew protocol with HTTP Digest authentication. Compatible with TetraPack and TMO.services server infrastructure.
WSS / TLS 443Adaptive Jitter Buffer
120ms prebuffer with adaptive playout. Handles network jitter, packet loss concealment, and automatic frame size detection.
480ms capacityTechnical Specifications
| Voice Codec | ETSI ACELP 7.2 kbps, 8 kHz, 30ms frames |
| Frame Format | STE (Speech Transcoder Equipment), 36 bytes/frame |
| Protocol | TETRA Homebrew (Brew) over WebSocket |
| Authentication | HTTP Digest (RFC 2617) |
| TX Latency | < 40ms (capture + DSP + encode) |
| RX Latency | ~150ms (120ms jitter buffer prebuffer) |
| DSP Pipeline | DC block → HPF → Spectral tilt → FFT NR+anti-alias → ÷6 decimation → Formant EQ → AGC → Compressor → Limiter → ACELP |
| QoS | DSCP EF (0xB8) voice priority marking |
| CPU Usage | < 20% during active transmission |
| Memory | < 50 MB steady state |
Compatibility
| Validated Devices | Hytera P50, P50 Pro, PNC460, PNC560, PDC760 |
| Developer Devices | Motorola LEX L10 |
| General Android | Any Android 5.0+ smartphone (Xiaomi, Samsung, etc.). Some consumer devices may deliver reduced voice quality due to bass-heavy microphones and high dynamic range characteristics not optimal for the ACELP codec by design. |
| Server | Brew protocol — TetraPack, TMO.services (WebSocket TLS, port 443) |
| Operation Mode | Half-duplex PTT (Push-to-Talk) |
| Audio Sources | Internal mic, wired headset, Bluetooth, USB audio |
System Requirements
Future Development
Device Validation
On-demand support for additional device validation and certification upon request.
Protocol Updates
Continuous protocol enhancements and feature updates aligned with TetraPack server development roadmap, as permitted by the TetraPack/BM team.
Changelog
- + Private Calls — simplex + duplex, floor control, incoming call dialog, auto-answer, call history.
- + TETRA Scan — Motorola-style TG scanning with per-TG priority and preemption.
- + Hamburger Menu — Private Call, Messages (unread badge), Scan, Settings, Exit App.
- + Mic Gain Slider — real-time adjustable from Settings.
- + Dream/MeigSmart PTT — hardware PTT key support for rugged devices.
- + Doze-resilient keepalive — alarm-based heartbeat for background reliability.
- + Exit App — proper service teardown from menu.
- + TX audio overhaul — new capture pipeline, rewritten DSP chain, directional mic beamforming.
- ~ Fixed PTT race condition, memory/thread leaks, service lifecycle, API 23 compat, DPAD navigation.
- ~ Native DSP loop fusion, LTO, compiler optimizations, reduced idle CPU wakeups.
- + SDS Messaging — send/receive text messages with delivery reports and notifications.
- + License management improvements and activation workflow refinements.
- + Production build optimizations and stability improvements.
- ~ Bug fixes and performance tuning from v1.1.2 field testing.
- + Hardware PTT support — configurable key code with auto-detect + broadcast intent for rugged devices.
- + On-Screen PTT toggle — hide software PTT button when using hardware PTT.
- + Voice formant EQ retune — improved mid-range clarity and intelligibility on TETRA networks.
- ~ Eliminated background noise when connected but idle.
- ~ Improved compatibility with older Android devices.
- ~ Profile selection now persists across app restarts.
- + Hytera-style signal indicator with connection state colors.
- + Responsive layout — VU meter and caller info visible on all screen sizes.
- + Compact caller info card with adaptive height.
- ~ Improved notification handling and status bar icon.
- + ISSI suffix support — login with extended subscriber identity (ISSI + suffix 01-99).
- + Refined voice presence tuning for improved clarity on repeater networks.
- + Redesigned TX audio dynamics processing for broadcast-grade output quality. Consistent speech levels with clean silence between transmissions.
- + Improved ACELP-to-AMBE transcoding compatibility with optimized spectral shaping and bandwidth management.
- + Enhanced mid-range voice presence for improved radio intelligibility.
- ~ Fixed UI layout issues on small-screen devices.
- + New high-fidelity 48kHz TX audio pipeline with spectral noise reduction and optimized downsampling to 8kHz ACELP.
- + Improved automatic gain control with faster convergence and better MEMS microphone support.
- + Responsive UI layout that adapts to all screen sizes, DPIs, and device form factors.
- ~ Fixed audio clipping issues on certain devices.
- + Advanced spectral noise reduction delivering professional-grade TX audio clarity.
- + Voice EQ profiling for natural radio voice character.
- + Consistent TX/RX VU meter scale for accurate visual feedback.
- + ETSI ACELP codec conformance validation.
- + Rebranded to TETRALink with refreshed visual identity.
- + Enhanced license management and activation workflow.
- + Security improvements and production build optimizations.
- + Improved TX audio quality with voice clarity enhancements.
- ~ Fixed audio artifacts and background noise during transmission.
- + Better speech detection preserving natural voice dynamics.
- + Initial public release with full TETRA voice support, secure authentication, hardware PTT, and reliable audio playback.
Licensing
RX (receive) is always free and unlimited. TX (transmit) requires a license.
TX License
- Unlimited TX on all groups & private calls
- Up to 3 devices per callsign
- All future updates included
- Professional DSP & noise reduction
- Works with TetraPack & TMO.services
- SDS messaging & TETRA scan
PayPal: paypal.me/YO3TCO
Include your callsign in the payment note.
Free License
- Full TX access forever
- All future updates included
- Up to 3 devices
- Recognition on this page
Granted by peer recognition — multiple ham operators must vouch for the nominee's merit and contributions to the community.
Frequently Asked Questions
How do I purchase a license?
How many devices can I use?
What if I change devices?
How does this compare to a TETRA radio?
What about offline use?
For questions or support, reach out to Chris YO3TCO on Telegram (@invictus747) or email yo3tco@gmail.com.