Silicon Labs EFR32 transceivers give access to filtered IQ samples on receive, so it's possible to make a multimode handheld transceiver using them.
There are two major versions of the hardware. The first version is built around a BRD4151 radio module and only works in the 2.3-2.9 GHz band. See hardware_v1/ for details.
The second version is built on a custom PCB and uses a dual band EFR32 chip. See hardware_v2/pcb/ for a KiCad schematic and PCB design. Construction is documented in hardware_v2 README file.
There is also a tutorial for flashing firmware.
The second version was initially designed for the 70 cm (432 MHz) and 13 cm (2.3 GHz) amateur radio bands. Later it was found that the EFR32 can be made to tuner over a much broader range. Matching circuits of sub-GHz path in current hardware are optimized for 70 cm but work reasonably well for lower frequencies as well. Modification for the 23 cm band should be possible but has not been attempted yet.
Tuning range has some gaps but covers the following frequencies:
* SSB is transmitted as a constant envelope signal by only modulating the frequency of a synthesizer. Amplitude variations are discarded and the synthesizer is made to approximately track the phase of an SSB modulated signal. This results is somewhat distorted audio and some splatter to neighboring channels, but it sounds surprisingly intelligible and has even received reports of good sound quality. During quiet moments, some carrier is added in order to have something to transmit.
Having a slightly dirty spectrum, this SSB transmitting trick may not be suitable for high transmit power on a crowded bands, but is probably acceptable for VHF/UHF contacts at low transmit power.
The firmware is released under the MIT license. It depends on the Gecko SDK from Silicon Labs, mostly licensed under the Zlib license.
I haven't decided on licensing of the hardware design yet.