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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I’ve made two of these based on older board designs and they work well. The software and hardware for this project are in a constant state of rapid advancement. I expect that will continue for at least another year–yielding a lot of new features.
It’s all open source/hardware and everyone working on it is a volunteer, so temper your expectations and attitude. The discord server is a good place to get support and to find out how to contribute to the project.
Oh no discord! Lol im too old for this 😁 i prefer an asynch approach, but probably if you are on a project full time discord has its beauty, who knows…
Ok great to hear, as all is OS/OSHW (I suppose minus the TRX board from Ali), it should also be possible to swap parts of the HW if something better is turning up at a good price. I got to know besides the RDA1846 there is also ADF7021 from analog amongst others.
Lets see maybe will get one in a while, but for now im on other projects, first time after my graduation back to ieee802.15.4, what a quantum leap compared to the cc2420 w/ AVR and what an improvement arduino is compared to those crappy 8051 C compilers of the era (cc2530 the chip we dumped for that)
Wishing all the best to those guys and their project
I got myself such a baofeng walky talky its cool for its price, as usual the SW is a bit moot, but this here seems in that regard better with a large touchscreen ui.
I just hope the RX is more sensitive than the beken chip in my walky talky
Any thoughts about using this for ft8 on 2m?
I don’t think those can do SSB…
H is aspirated in most English words, so “a ham” (except of course silent h words like “an honor”)
I modded one of these with the UHF board for a fellow ham. He says it works like a champ but the audio is too hot.
73 de kd6mtw
Nice where can I get one
Hi, I really like this project! I did a small review about the RFinder B1+, it’s an integrated Analog/DMR/Android device, but a modular like yours is more interesting. A UHF module or (both VHF/UHF) could have a lot of potential! Do you expect a DMR/Tetra version?
73, Yves, ve2ymm
How to purchase one?