# LinHT-hw
**Open-source, Linux-based, SDR handheld transceiver**
[![CC BY-NC-SA 4.0][cc-by-nc-sa-shield]][cc-by-nc-sa]
[](https://m17-project.github.io/LinHT-hw/)
## What is LinHT?
**LinHT** is an open-source handheld **software-defined radio (SDR) transceiver**
built around a modern Linux System-on-Module and a true IQ RF front-end.
It is the **successor of the OpenHT project**, with focus on:
* simpler and more maintainable hardware,
* no FPGA in the signal path,
* tight integration with Linux, GNU Radio, and modern SDR tooling,
* long-term openness and hackability.
LinHT is developed by members of the [**M17 community**](https://m17project.org) and is intended primarily
for **radio amateurs, SDR experimenters, and developers**.
This repository contains the **hardware design files** for LinHT.
> ⚠️ **Important**
> LinHT is **not a consumer product** yet.
> It is an experimental, community-driven open hardware project.
## Key ideas behind LinHT
* **True SDR**: IQ baseband access, not FM-only
* **Linux-first**: no microcontroller firmware lock-in
* **No FPGA**: easier development, lower entry barrier
* **Open everything**: hardware, software, toolchains
* **Hackable handheld**: not just another black box walkie-talkie
## Hardware overview
LinHT is built around a Linux SoM and a wideband IQ transceiver.
* **System on Module:** [CompuLab MCM-iMX93](https://www.compulab.com/products/computer-on-modules/mcm-imx93-nxp-i-mx-93-som-smd-system-on-module)
* **RF front-end:** [Semtech SX1255](https://www.semtech.com/products/wireless-rf/lora-core/sx1255)
**CPU**
* Dual-core ARM Cortex-A55 @ 1.7 GHz
* ARM Cortex-M33 coprocessor @ 250 MHz
* Floating-Point Unit
* ARM Ethos-U65 microNPU (TensorFlow Lite support)
**Memory**
* 2 GB LPDDR4
* 32 GB eMMC
### RF capabilities (revision B target)
| Parameter | Value |
| --------------- | ------------------------------------------------------------- |
| Frequency range | **UHF band** (exact limits depend on PA/filter configuration) |
| Bandwidth | up to **500 kHz IQ** |
| Architecture | Direct IQ (complex baseband) |
| TX power | up to **~5 W** (revision B, internal PA) |
| RX features | Programmable attenuation, gain control |
| Modes | FM, SSB, M17, experimental digital modes |
> 📌 **UHF only!**
> VHF support is frequently requested, but **is not planned for revision B**.
> The current priority is **stability, manufacturability, and software maturity**.
## Software overview
LinHT runs a **custom Yocto-based Linux distribution** designed for SDR and
embedded radio use.
### Supported development models
* C / C++
* Python
* GNU Radio flowgraphs
* SoapySDR
* Custom DSP pipelines
Standard Linux tools (gcc, gdb, strace, etc.) are available directly on the device.
### Supported modes (current status)
* ✅ FM (TX/RX) with pre-/de-emphasis and CTCSS
* ✅ SSB (TX/RX)
* ✅ **M17** (TX/RX)
* ✅ TETRA (RX only)
* 🧪 Experimental 64-QAM @ 2 Mbps
* ⏳ Planned / possible: FreeDV, APRS, packet radio, custom modulations
## Hardware revisions
LinHT is developed iteratively. Each revision serves a specific purpose.
| Revision | Status | Purpose |
| ---------- | --------------------------------------------- | -------------------------------------------- |
| **Rev. A** | Completed | Early prototype, architecture validation |
| **Rev. B** | In progress | Feature-complete, manufacturing-ready design |
### Revision A
* Manufactured earlier in 2025
* **4 assembled prototype units**
* Used to:
* validate the Linux + SDR architecture,
* bring up SX1255 under Linux,
* start software and DSP development,
* identify mechanical, RF, and power issues
* Revision A was **never intended for production**.
### Revision B (current focus)
* Incorporates lessons learned from Rev. A
* Major improvements:
* redesigned power supply
* internal PA (~5 W)
* improved RF path and attenuation for RX
* cleaner layout and grounding
* **Not yet released for manufacturing**
> 📅 **February 2026 status**
> A test batch of Revision B PCBs is currently being assembled.
> Please check this page later for updates.
## Repository contents
This repository contains:
* KiCad 9.0 project files
* Schematics
* PCB layout
* Manufacturing outputs (generated automatically)
Gerbers, BOM, pick-and-place files, and schematics are:
* generated automatically via **GitHub Actions**
* published on [**GitHub Pages**](https://m17-project.github.io/LinHT-hw/)
## Required hardware (donor radio)
LinHT is designed as a **replacement mainboard** for the
**Retevis C62 handheld radio**. You will need:
* a Retevis C62 (donor device)
* its:
* enclosure
* display
* keypad
* battery
* connectors
More details (Rev. A focused, older but useful): [LinHT Open SDR Handheld For Radio Amateurs](https://uart.cz/2811/linht-open-sdr-handheld-for-radio-amateurs/)
## Firmware images
Prebuilt Linux images for LinHT are available here:
[https://m17project.org/linht/](https://m17project.org/linht/)
Documentation:
* [https://wiki.m17foundation.org/index.php?title=LinHT_Image_Build](https://wiki.m17foundation.org/index.php?title=LinHT_Image_Build)
Yocto layers:
* [meta-linht-hardware](https://github.com/M17-Project/meta-linht-hardware)
* [meta-linht-software](https://github.com/M17-Project/meta-linht-software)
* [meta-linht-sdr](https://github.com/M17-Project/meta-linht-sdr)
## Flashing the device
Flashing is done using **NXP Universal Update Utility (uuu)**.
1. Boot LinHT into flash mode
(hold the secondary side button while powering on)
2. Flash using:
```bash
uuu -v -b emmc_all imx-boot-mcm-imx93-sd.bin-flash_singleboot linht-image-mcm-imx93.rootfs.wic.zst
```
Tool download: [mfgtools](https://github.com/nxp-imx/mfgtools/releases)
To access LinHT’s USB network device on Windows, install the **RNDIS driver**: [microsoft.com USB RNDIS Gadget](https://www.catalog.update.microsoft.com/Search.aspx?q=USB%20RNDIS%20Gadget)
## Documentation & Wiki
Primary documentation lives on the **M17 Wiki**:
* [LinHT overview](https://wiki.m17foundation.org/index.php?title=LinHT)
* [Image build instructions](https://wiki.m17foundation.org/index.php?title=LinHT_Image_Build)
* [Image usage & manual](https://wiki.m17foundation.org/index.php?title=LinHT_Image_Manual)
## Contributing
LinHT is a **community project** and contributions are welcome. The best way to
get involved is [**joining the M17 Discord**](https://discord.gg/4brEP8wwVp), look for channel: **#linht**.
This is the preferred place to:
* discuss ideas,
* coordinate work,
* ask questions,
* avoid duplicated effort.
Other ways to contribute:
* Open issues in this repository (design notes, questions, suggestions)
* Help on the **software side** (especially welcome):
* Yocto recipes
* device tree improvements
* CI / GitHub Actions
* build automation
* Explore and extend [LinHT-utils](https://github.com/M17-Project/LinHT-utils)
If you’re an experienced **embedded Linux or SDR developer**, we would love
your help.
## FAQ – Frequently Asked Questions
### ❓ Where can I buy LinHT hardware?
You currently **cannot buy LinHT as a product**. To build LinHT, you need to:
* manufacture the PCB yourself (using provided Gerbers),
* source components,
* assemble the board,
* use a **Retevis C62** handheld radio as a donor for:
* enclosure,
* display,
* keypad,
* battery,
* connectors.
This may change in the future.
### ❓ Is LinHT suitable for everyday radio use?
Not yet. And maybe never in the "consumer radio" sense. LinHT is currently best
suited for:
* developers,
* radio amateurs comfortable with Linux,
* SDR experimenters,
* people who enjoy building and debugging hardware.
You should **not** expect:
* plug-and-play user experience,
* polished UI,
* certification,
* warranty,
* commercial-grade RF compliance.
### ❓ Does LinHT support VHF?
**No, not in revision B.**
VHF support is a **frequently requested feature**, but it is
**not planned for revision B**, adding another band significantly increases:
* RF complexity,
* filtering requirements,
* PCB area,
* development time.
Right now, the project is focused on:
* stabilizing the hardware,
* finishing revision B,
* improving software and DSP,
* validating the new power amplifier and RF chain.
VHF is **not ruled out** for future revisions, but it is
**not a current priority**.
### ❓ Is LinHT certified / legal to transmit with?
LinHT itself is **not certified**. Responsibility lies with the builder and
the operator. LinHT is intended primarily for:
* amateur radio use,
* experimental licenses,
* lab and research environments.
Always follow your local radio regulations.
### ❓ I want to help. Where do I start?
The best starting point is **discussion**. Join the M17 Discord, channel: **#linht**.
Good ways to contribute:
* software development (Yocto, drivers, tooling),
* testing and feedback,
* documentation,
* RF/DSP experiments,
* CI and automation improvements.
If you’re unsure where to help - just ask.
## License
This project is licensed under: **Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International**
You are free to:
* share
* adapt
Under the conditions:
* attribution
* non-commercial use
* share alike
[![CC BY-NC-SA 4.0][cc-by-nc-sa-image]][cc-by-nc-sa]
## Acknowledgements
LinHT is developed by the **M17 community**, with contributions from many individuals.
Thanks to everyone testing prototypes, reviewing schematics, writing software, and sharing ideas.
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