kv4p HT is an open-source hardware VHF or UHF radio designed to plug into the USB-C port of an Android smartphone and turn it into a handheld ham radio transceiver. It’s based on an ESP32 wireless module and an SA818 radio module.
This accessory makes your phone capable of off-grid voice and text communication with a Technician-class amateur radio license. It’s small enough to fit into a pocket, partially because it does not need a battery, relying on the built-in battery of your phone.
kv4p HT V2.0 specifications:
- Wireless module – ESP32-WROOM-32E-N4
- SoC – ESP32 dual-core Tensilica LX6 microcontroller @ up to 240 MHz with 520KB SRAM
- Storage – 4MB flash
- Wireless – 2.4 GHz WiFi 4 and Bluetooth 4.2 BR/LE connectivity, built-in PCB antenna
- VHF Radio
- SA818-V radio module or DRA818V (134 – 174MHz)
- VHF low-pass filter
- SMA antenna connector
- Tx Power – Up to 1 Watt for several miles/kilometers range without draining your phone’s battery excessively
- Note: while the project focuses on VHF communication, UHF can be supported via SA818-U (400 – 480MHz)
- Features
- Supports texting with notifications just like SMS — radio-based APRS messaging (not just location) with built-in 1200 baud modem
- “Crystal-clear” 44kHz 8-bit ADC/DAC audio with filter and squelch
- Live closed captions on supported phones
- Scan through unlimited memories and groups
- Automatically find nearby repeaters using GPS
- Sticky PTT (Push-to-Talk) with haptic feedback
- USB – 1x USB-C port for connection to a smartphone
- Misc
- Program, Reset, and PTT buttons
- LEDs
- USB-C to USB-C adapter
- Power Supply- Via USB-C, no built-in battery
- Dimensions – PCB: 82 x 38mm
Note that the specifications and photos above are for version 2.x of the board, as previous iterations required the users to add his/her own ESP32 board to the SA818 board.
It’s a completely open-source hardware design licensed under GPL3, and the source code for the kv4p HT Android app and ESP32 Arduino firmware, as well as EasyEDA PCB designs, and 3D printer files can be found on GitHub. The instructions to get started and contribute to the project are all shared on the project’s website.
While you could build the kv4p HT by yourself since it’s an open-source hardware project, most people would likely purchased a Android smartphone ham radio kit on Halibut Electronics or Chelegance. A vendor also sells both VHF and UHF versions on AliExpress for about $51, but people complain that the device sold there keeps coming out of the USB Type-C port… Finally, you can also find 2 kits on Amazon for $54.
Thanks to onebir for the tip.
Jean-Luc started CNX Software in 2010 as a part-time endeavor, before quitting his job as a software engineering manager, and starting to write daily news, and reviews full time later in 2011.
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