Four Days in May (FDIM) is an annual QRP convention that is held in Dayton, Ohio. A series of talks are usually given and for the 2022 event, there was an interesting presentation given by Hams Summers (G0UPL) about his new QDX transceiver kit.
This is a 5-watt radio for the 80m, 40m, 30m and 20m bands and is designed for digital modes like FT8. The basic kit currently retails for just $69 but there may be additional costs like import duties. It is still a very cost effective way of getting on the bands especially when you consider how many main brand radios costing $1000++ must be sitting on one frequency doing FT8 day after day.
Hans writes on his website… “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 QDX is supplied with the surface mount parts already on the PCB but some level of experience is still required to build and assemble this kit. I don’t think it’s for absolute beginners.
The power output versus the supply voltage is shown above. As the frequency is relatively low… 3.5 MHz to 14 MHz… the performance of the output stage is pretty good.
Hans did mention that there are plans for a similar radio covering 20m to 10m …14 MHz to 28 MHz… and the challenge then will be to have a reasonable output at the higher frequencies.
Demand for this kit has been huge so check on the QRP Labs website for availability. There is also a lot more information about the radio on that site.
The presentation itself covers the basics of digital modes before exploring what is going on in the QDX radio.
The video of the presentation which was only put up on YouTube on the 14th of November 2022 is about an hour long but the audio level is very low. I had to use headphones to listen to it.[embedded content] Source