Digitrex Tv Manual

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James Talbot

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Aug 3, 2024, 4:43:36 PM8/3/24

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QDX is suitable only for single tone FSK modes, which covers the majority of digital modes in use today. This includes everything in WSJT-X, JS8Call, some fldigi modes e.g. RTTY, Olivia and more. QDX is not suitable for on/off keyed modes such as CW because it does not have click-reducing RF envelope shaping; furthermore it is not suitable for phase shift keyed modes such as PSK31 or modes involving multiple concurrent tones such as WinLink,

The Optional enclosure is black anodized extruded aluminium, very sturdy and elegant. The enclosure size is 89 x 63 x 25mm without protrusions. The front and rear panels are drilled and cut to match the QDX PCB with laser-etched lettering. The enclosure includes four self-adhesive feet.

QDX works well on 60m, as documented by John AE5X at -analysis-qdx-on-60m.html. Outside the range 3.4-14.5MHz, QDX can be used as a receiver, with some loss of sensitivity. Firmware versions 1.06 onward can operate on any amateur band from 2200m to 4m, but hardware changes will be needed (correct filters etc).

NOTE: Due to the global semiconductor shortage, the price of many ICs has increased dramatically, and there have also been (less drastic) price increases in other parts of the production. Accordingly it has been necessary to pass on some of these costs to the price of the QDX, this is why it is now $69 when the original price was $60 for the first batch. The first batch was produced in Jan 2020, a whole world away.

There are three types of USB devices in QDX: USB Audio, USB Virtual COM port, and USB mass storage (like a USB Flash memory stick) for firmware update. Drivers for all of these types of audio device are already present on your PC if you are using Mac, Linux, MS Windows 10 or MS Windows 11. If you are using older versions of Windows, then you need to install a driver for the Virtual COM port (audio and USB Flash drivers are already present even on older Windows), the details are in the QDX manual.

Please MAKE SURE you use the correct documentation for your PCB Revision and your firmware version! Batch 1 (Rev 1) PCBs were sold in October 2021 and do not have a PCB Revision printed on them. Subsequent PCB revisions have a large "Rev 2" (etc) printed on the PCB silkscreen.

You need THREE manuals, one contains the Operating instructions, one contains the Assembly instructions for the output transformer, and one contains the remaining assembly instructions, theoretical design information, and performance measurements.

Please refer to the manual for the firmware update procedure, which is very easy and does not require any special hardware, software, drivers etc. It requires only a PC and a USB cable. Click the file in the first column of the table below, to download the firmware file of interest. Note that firmware files are encrypted and can only be used on the QRP Labs QDX.

The first thing was to change the QDX configuration using my terminal emulator to only require one sample of tone before setting the output frequency (the default being 480). This is to allow the QDX to keep up with the tone frequency potentially changing every 22mS.

Next, under the rig control option, select Hamlib and check the "Use Hamlib" box at the top.
The rig should be Kenwood TS440S, device is COM3 (i.e. whatever you use with your terminal emulator to get to the QDX menu) and check the box "PTT via Hamlib command". Other items can remain at their default values. Finally, press the "Initialize" button to make it all work.

Expect to spend an hour or two browsing the help files to see how to operate the various buttons and options. One thing which I found difficult to find was how to turn on the Rx Monitor to hear what's going on on receive. This is done from the "View" menu: choose the top option "Rx Audio Dialog". On my setup, the received audio was very quiet for some reason. Maybe I will discover how to adjust it to a reasonable volume in due course.

By the way, I spent an hour or two wondering why the QDX wasn't going into transmit, to find that I had not checked the "Use Hamlib" box for rig control. Quite exasperating, but with perseverance I got there: it does work, so I am happy!