Kv4p HT – A homebrew 1W radio (VHF or UHF) that plugs into an Android phone

KV4p HT is an open-source hardware and software project that transforms an Android phone into a 1-watt VHF or UHF radio, requiring users to assemble the device themselves. The project is designed for amateur radio enthusiasts with at least a Technician license and offers features like APRS, GPS, and text messaging.

The KV4p HT kit includes a PCB with a radio module (such as SA818-V or DRA818V), and the project’s firmware and app are fully open source under GPL3 licensing. Users solder the components onto the PCB, attach it to their phone using sticky gel pads, and connect an antenna. The device draws power directly from the phone, eliminating the need for a separate battery.

The Android app, compatible with devices running Android 8 or higher, provides a full suite of amateur radio features, including a 1200 baud modem for APRS, position beaconing, and haptic feedback for push-to-talk. The firmware and PCB designs are available on GitHub, with options to order pre-assembled kits or source parts independently.

Why It Matters

This development matters because it offers a low-cost, customizable alternative to traditional ham radios, potentially expanding access to amateur radio communications. Its open-source nature encourages innovation and community involvement, while the integration with smartphones makes it convenient and versatile for emergency preparedness, field operations, and hobbyist experimentation.

Background

The project builds on the growing trend of open-source hardware for amateur radio, combining modern microcontrollers like ESP32 with readily available radio modules. You can learn more about controlling smart devices with your voice. It follows recent interest in portable, smartphone-integrated communication devices, and addresses the need for affordable, easy-to-assemble radios for hobbyists and emergency responders. Prior projects have focused on standalone radios or software-defined radio, but KV4p HT emphasizes simplicity and accessibility.

“KV4p HT is an open-source project that lets you build a portable ham radio that integrates seamlessly with your Android phone, offering advanced features like APRS and GPS.”

— KV4p (creator of the project)

“It’s impressive how the project leverages existing phone hardware to create a functional ham radio, making amateur radio more accessible.”

— Hacker News community member

What Remains Unclear

It is not yet clear how the device performs in real-world conditions, including range, reliability, and battery life under various usage scenarios. The project also requires a Technician license, which may limit immediate adoption among casual users.

What’s Next

Next steps include wider testing by the amateur radio community, potential refinement of the firmware, and the development of beginner-friendly kits or instructions. For testing and device options, see Android phones for app testing. Further updates may include enhanced features or integration with other digital modes.

Key Questions

Can I use the KV4p HT without a license?

No. Operating the device requires at least a Technician class amateur radio license, according to FCC regulations.

What equipment do I need to build the KV4p HT?

You need a PCB (which can be purchased as a kit or assembled from parts), a radio module (such as SA818-V), an antenna, and an Android device running Android 8 or higher. The project provides PCB designs and firmware for DIY assembly.

Is the project suitable for beginners?

Building the device involves soldering and some technical knowledge. It is recommended for hobbyists comfortable with electronics assembly and firmware flashing. For more on device compatibility, check out rugged Android phones for testing.

What features does the KV4p HT support?

It supports 1W VHF/UHF transmission, APRS for position and messaging, GPS integration, and a full-featured Android app with haptic feedback and animation controls.