The QDX is a tiny FSK mode transceiver from QRP Labs which works amazingly well. This week, new firmware was released which improves transmit a little. I've been running it on 40m here and results are very good.
My friend Stephen, VK2BLQ, is 800km away in Sydney and he received my 3W at +18dB last evening.
I have a theory that direct generation of RF for digital modes in rigs like the QDX produces a cleaner signal than you get by mixing audio up to RF in a sideband radio and so decodes are better.
At a similar time I had a transmit cycle that was spotted by 45 stations around the world.
Changes in 1.04:
- Resolution to the Rev3 PCB "popping" issue (RF discontinuities during TX).
- Audio streamed to the PC during Transmit is now set to zero (silence).
- 50 millisecond transmit timeout on cessation of audio from PC (protects QDX e.g. if PC crashes).
- No CAT command TX timeout (configurable enable and timeout duration).
- Removed unnecessary 48ksps clock domain sync PC vs QDX.
- Enables PTT output connector, with grounded and +5V outputs individually controllable by band.
- 12kHz IF offset is removed when you enable IQ Mode.
- Transmit is disabled when you are in IQ mode.
- Gain is now in dB.
- Gain is now configurable per band.
- New "Band Configuration" screen where you can configure the list of supported bands.
The firmware upgrade process couldn't be easier. You interrupt the power up cycle and then re-plug the device. It mounts as a disk drive and you drag over the firmware.
After running for a few days on 40m I see I'm #3 on the WSPR Challenge for receiving.
Hard to beat Phil, VK7JJ though!