Thursday, July 21, 2022

Updated QDX Firmware to 1.04 - working very well on WSPR

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!

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