QDX rev3 from QRPLabs

Hi all,
Maybe this new QRP TRX will interest few activators :wink:

New kit: QDX - QRP Labs Digital Transceiver
Sat, 09 Oct 2021 09:30:26 UTC

Hi QRP Labbers

I am pleased to announce at last the availability of the new QDX transceiver. I actually developed this nearly two years ago but a lot of things got in the way of finishing the final touches to the firmware and documentation… ya know, Covid19, a new baby in the house, and of course QCX-mini and all it’s associated teething troubles, along with keeping QRP Labs going…

QDX will cost $60 and the optional enclosure will cost $20.

The shop page is QDX 4-band 5W Digi transceiver

Ordering will open at 1800Z on Monday 11-Oct-2021.

The main QRP Labs page is QDX Digital Transceiver

Between now and Monday, you can read the manual and ask any questions. Please understand and read the manual before ordering.

So QDX… a four band 5W digi modes transceiver 80, 40, 30 and 20m. It produces 5W from a supply voltage of 9V using a new Class-D Push-Pull amplifier I developed specially for it. Most importantly, this is NOT an SSB transmitter! It suits any single FSK mode (such as FT8, JS8Call, WSPR, JT4, JT9, JT65 and more). It performs an analysis of the audio output by the PC program (e.g. WSJT-X) to determine the audio frequency then commands the Si5351A Synth to produce that frequency. As such, there is NO unwanted sideband transmission, NO residual carrier transmission, and NO IMD products due to amplifier non-linearities. Just efficient, clean transmission.

The QDX receiver is a high performance SSB received using an embedded SDR, with a high performance 110dB dynamic range, 24-bit, 48ksps stereo ADC chip and 32-bit ARM Cortex M4 processor.

All band switching and transmit/receive switching is solid state. No plug-in modules here, no relays. Everything is electronically switched by CAT control automatically when you change the band drop down in WSJT-X.

QDX also includes a 24-bit 48ksps stereo USB sound card for audio, and a USB Virtual COM serial port for CAT. Transfer of audio from WSJT-X to QDX is noise-free, lossless, just a pure transfer of digital sample information. Transfer of audio from QDX to the PC via the USB sound card is high fidelity without possibility of ground loops. No audio cables, no headaches - just a single USB cable between PC and QDX carries both audio and CAT commands. QDX has only three connectors: DC power, USB and RF (to the antenna).

The VFO is a Si5351A Synthesizer under CAT command from the PC. So it covers any digital frequency, not just limited to FT8 for example. QDX includes a 25MHz TCXO module as standard, as the reference for the Si5351A Synthesizer.

QDX includes its own internal signal generator and test tools suite too. You can connect a terminal emulator to it and explore the performance and techniques that make it work, as well as enter any specific configurations you may need. However the terminal application mode is not necessary for ordinary operation and most users will not need it.

QDX includes the QFU (QRP Labs Firmware Update) bootloader so lifetime free firmware updates are easy to install, just by loading the new firmware file into QDX using File Manager on your PC: works on any OS, no drivers, no software, no hardware e.g. programmer.

Due to an unfortunate self-resonance QDX assembly requires removal of four 47uH SMD inductors that are to be replaced with four axial leaded inductors (supplied). Furthermore, since QDX uses the AMS1117 voltage regulator, an additional electrolytic capacitor is supplied that must be soldered to connections on the top side of the board. Other risks of using the AMS1117 are mitigated by the fact that QDX has no ports where hot-plugging or shorts could cause any danger of AMS1117 failure - so this is not a risky situation as the first batch QCX-minis had.

The optional QDX enclosure is the same aluminium extrusion as used in the QCX-mini but of course is cut, drilled and laser-etched differently.

Initially, I produced a batch of 500 QDX, which I actually manufactured back in January 2020 before the Covid19 pandemic got started. On Monday 11-Oct-2021 at 1800Z I will put a quantity of 450 QDX in the shop, for ordering. What of the remaining 50… well quite a few didn’t make it through the firmware development and testing (when developing the QFU bootloader, I bricked quite a few QDX!)… and I am going to hold a few back in case of issues etc. losses in shipment, etc etc.

Due to the global semiconductor crisis, several of the ICs used are currently unavailable so I do not know when the next batch of QDX can be made available. I will begin researching sources or alternative ICs.

So - any comments and questions are welcome, the manual is there, available to read and understand so you can decide whether you would like to order one.

73 Hans @G0UPL


73 Éric


I am not affiliated with QRPLabs but I love these QRP products,
See some photos

73 Éric


It looks interesting, I may join the fight on Monday to order one. Of course QRP labs produce a range of great QRP CW rigs and this is the first pure digi-modes rig. The way the rig works was explained in Hans’ email and what is one of the first questions some goon asks? “No CW?” SBJ… this is for digimodes driven from a PC. There always has to be one…


Sorry Andy no CW, we all waiting for the QSX :slightly_smiling_face:
I think you can say how many digital SOTA QSO (activator’s) are on the database !
I work sometime on FT8 summits actives but I don’t particularly like this mode, Hans says we can use it in RTTY and other modes, for the weight and price of this QRP I think it’s worth it and it’s already mounted and I will surely take one :yum:
Let’s wait for today’s activators to read this info :upside_down_face:

73 Éric

Looks like a good option for multi-day trekking if you’re a no-code ham. Could tempt some people out on the trail.
73 Matt


Here a video.

QDX Video now live…

Date: Sat, 09 Oct 2021 14:51:39 UTC

Including sneak preview of the new QRP Labs offices…

73 Hans G0UPL "

73, Éric


Anybody have any luck getting hold of one of these today? 1800 came and went, out of stock.
Good luck

Tim, come on now, they haven’t gone on sale yet.

Twenty minutes and Hans open his shop :wink:

From Hans message :

“” The first batch are 80 40 30 20 only. When the dust settles I do hope to make versions for different bands such as a high band version. “”

Maybe we can wait for new sun cycle…

73 Éric

Lol, Google was not my friend.
Panic over…
Good luck all


Got one :wink:

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Got one.

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I got to stage 3 of the checkout and it stopped.

:innocent: Thank god it wasn’t me… Luckily I read the info!! Phew!!!

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Crashed 4 times whilst checking out, just received the confirmation. Happy days…

500 kits sold out for less than 15 minutes.
It is more faster than QCX mini =)

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440 have been sold.