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Intro

For help, please see the DDX manual. To purchase an assembled and fully tested DDX-Commercial board please reach out to us over email.

The 'Direct Digital Transceiver' (DDX) project. DDX is a radio transceiver (rig) which is rugged, simple and reliable.

DDX-1 is a 'silent' radio which can be heard almost all over the world!

Current versions:

  • DDX-Commercial-7: 5W+ digital transceiver (Commercial, Latest Upgraded Version)

  • DDX-1 R1.10: 5W digital transceiver (FOSS)

For a truly portable backpack setup you can combine DDX with the FT8 Radio Android app.

Demo Pic 0

Sample QSO (from Pune to Medellin on 10m, 15691km) on DDX-1:

Medellin QSO

QSO with Paraguay:

Paraguay QSO

Who doesn't want a QSO from Medellin after binge-watching Narcos? ;)

Another sample QSO with WW1WW (Pune to USA):

USA QSO

Render (DDX Commercial)

DDX-Commercial-1

5W+ transceiver based on Pico 2 MCU platform. Beats IC-705 in terms of efficiency and power consumption!

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 (1:10 SWR tested). 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 (tested against OTH radar + 100 kW AM station in close visual proximity)

  • No toroids 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 (https://github.com/kholia/DigitalRadioReceiverSupport/). 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)!

  • 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.

  • Low cost (cost-effective)

  • Stress tested by WSJT-Z for multiple days

  • DDX-1 routinely receives FT8 traffic from 80 to 100+ countries using a simple 5m long EFHW antenna.

RX Performance

RX Performance

Performance of CD2003-with-BPF is >= 80% of that of RSP1 SDR, at least!

I live right next to a 100 kW AM station (Pune AIR @ 792 kHz). Also, there is an OTH radar nearby operating close to 28 MHz!

TX Performance

TX Performance

VFO stability

It receives WSPR @ 28 MHz ;)

Stability

WSPR TX Performance

WSPR TX Performance

QSOs

DDX-1 has already made hundreds of QSOs on air.

QSOs!

QSOs 2!

Power sources

DDX-1 was tested with the following power sources.

  • SUGON 3005D Adjustable Digital DC Power - RECOMMENDED

  • USB battery bank with PD 3.0 and >= 35W output and 15V or 20V PD decoy module (RECOMMENDED, safe, portable, durable)

  • RUIDENG DPS5020 power supply module (@13v) powered by MEAN WELL / Mornsun SMPS

  • 3S "12V" Li-ion 18650 battery pack (can be "volatile")

Safety Tips

  • Use a Common-Mode-Choke (attached between the rig, and the antenna) for safety against return/back RF.

Resources

Joining In

Are you interested in such projects, and spam-free technical discussions?

If yes, you might be interested in joining the 'HAMBREWERS' Telegram group.