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
- + Updated TetraPack compatibility with the latest Brew protocol requirements.
- + Aligned connection behavior with Brew v1 and Terminal mode for smoother network entry and reception.
- ~ Refined interoperability while keeping the hardened production build and open HAM-radio use model.
- + Paid licensing removed — TETRALink is now open right-to-use for HAM radio, with future development funded by donations.
- + Public release APK cleaned for distribution — debug capture removed from production builds, release logging reduced, output stripped.
- + Hardened shipping build with stronger obfuscation, native symbol stripping, and explicit non-debuggable release packaging.
- ~ Better rugged-device behavior for hardware PTT, private-call routing, reconnect handling, and clean app exit/restart flows.
- ~ Audio settings refined with live speaker playback gain trim/boost for easier device-by-device field tuning.
- + 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.
Open Right-to-Use for HAM Radio
There is no licensing. RX and TX are both open and unlimited for HAM-radio use. Future development is supported by voluntary donations.
HAM-Radio Right to Use
- Full TX and RX access on supported HAM-radio networks
- No licensing gate, activation key, or hardware-ID exchange
- Use it on your own supported HAM-radio devices
- All future public updates included
- SDS messaging, scan, private calls, rugged-device UI
- Works with TetraPack & TMO.services
Use it freely for HAM-radio operation.
Donations are welcome only if you want to support what comes next.
Future Development Fund
- Funds rugged radios and phone compatibility validation
- Helps interoperability work with TetraPack and related services
- Supports fixes, regressions, and release hardening
- Supports future development while keeping use rights open
- Direct line for deployment feedback and support
- PayPal or Telegram, whichever is easier for you
If TETRALink is useful for your daily operating, emergency readiness, or field experiments, consider sending a donation back into the project.
Thank you to everyone who helped develop the TETRALink project, whether through financial support or through rigorous, continuous testing, reported feedback, and feature requests that contributed to what TETRALink is today.
If you bought a TETRALink license in the past and want to be listed as a project sponsor, contact Chris YO3TCO. Sponsors receive preferential support, early access to releases, and optional beta-testing access if they want to join.
Frequently Asked Questions
Do I need a license or activation?
How can I support the project?
I bought a license in the past. What happens now?
How many devices can I use?
What changed in the latest release?
How does this compare to a TETRA radio?
What about offline use?
Donations are optional. For questions, support, or deployment feedback, reach out to Chris YO3TCO on Telegram (@invictus747) or email yo3tco@gmail.com.