kv4p HT is a homebrew VHF radio that makes your phone capable of voice and text communication completely off-grid with at least a Technician class amateur radio license.
The radio simply plugs into the USB C port on your Android smartphone and transforms it into a fully-fledged handheld radio transceiver. It’s completely open source (GPL3): the Android app, ESP32 firmware, PCB designs, and 3D printer files.
It’s small enough to fit in your pocket and take anywhere, and since it has no internal battery it’s the perfect radio to put in a go-bag or your car’s glove compartment.
NOTE: kv4p HT is an open source project you build yourself and has absolutely no warranty, or guarantees on functionality or reliability!
Can be built with parts costing a total of $35 (approximately 5,300 yen ~ 34 USD).
