Acknowledgement: Thanks to Dhiru Kholia who designed this TRX and for sharing it to the Radio Amateur Community.

What is it?

The 'Direct Digital Transceiver' for short DDX is a radio transceiver (rig) which is rugged, simple and reliable. It is based around the original Barb ADX design Radio frontend and uses an RP2040 at it's core.

Features (DDX-1)

Single USB-C cable for handling both Audio + CAT control

True 5W output on all HF bands. It even outputs ~1-2 W @ 50 MHz! (We now just need a 6m capable receiver section to build a 6m digital transceiver).

Rock-solid PA which handles open, short, and bad SWR conditions. We knowingly stress-test it with untuned antennas and still manage DX (not a recommended practice for sure though).

Rock-steady VFO which does NOT drift even under exposed conditions. Yes - it receives WSPR at 28 MHz just fine.

Reliable T/R switching based on a DPDT relay

Switchable BPF support to get rid of BCI and other interferences

No toroid's to wind (assuming an external LPF bank is in use) ;-)

The IRF510 final remains as cool as a cucumber (Class-D operation) - a small heat sink is more than enough.

Avoids problems associated with the 'audio frequency counting' approach used by earlier designs. DDX-1 has a bit-perfect, deterministic TX output.

It works beautifully with the 'FT8 Radio' app GitHub. The 'FT8 Radio' app handles FT8 decoding well in real time (Native MCU decoders offer significantly reduced performance at the moment). The app can decode 35++ stations at a time, and even large screens can fill up very rapidly - such is the receiver's performance (with a BPF)!

Supports largely automated assembly from JLCPCB (all the required files are in the same GitHub repository)

DDX-1 comes with a free, open-source AGPLv3 licensed firmware.

No calibration is (ever) required. Just pick up DDX-1 and it is ready to go on air.

What is Included?

Pack of 2 PCB'S - Mainboard and VFO board