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(tr)uSDX

There are quite a few small QRP rigs about nowadays. Some of them are pretty basic like the Rockmite type (which by the way doesn’t make them bad!) and some are a bit more advanced like the MTR range from LNR Precision. You may be familiar with the Hans Summer QCX design which has sold in its thousands although it was a single CW only rig. It was simple to assemble and a good performer.

The uSDX, micro SDX, (or rather as it is called now the (tr)uSDX after a load of cheap Chinese knock offs bearing the uSDX name appeared on the various marketplaces that trade in that kind of stuff) is an off shoot of the QCX. It takes a similar principal in as much as the architecture is similar but it is a multi band CW and SSB rig.

Its fair to say that he development of the rig has been on the cards for some time and it has gone from a through hole, multi board construction through to its (final) iteration as a 2 board SMD device. This revision is expected to be the last from DL2MAN but it is a useful piece of kit none the less.

Assembly

I was lucky enough to be on the right groups.io conversation at the right time and managed to get in the UK group buy. 50 of us managed to get hold of a pair of boards after Ian, MM0GYX did all the hard work sourcing parts that couldn’t be supplied as part of the PCB manufacturing assembly. So not only was I lucky to get in on the group buy I also got 2 completely assembled boards with only a few toroids to wind and some minor assembly. The instructions are on video and very good.

There 13 toroids to wind, some relays that need a bit of a tweak, an OLED that needs a couple of caps removed and a mod to the supply as part of a charge pump modification. Add in the switches, a speaker and mic and 3.5mm sockets all adds up to around about half a days work if you plod on at my speed.

To give you a sense of scale the markings on the mat below are 1cm wide. So in total the boards are about 865cm x 55cm.

Here we are with the boards sandwiched together. The RF board sits directly below the main board using a low profile pin header and the case is a 3D printed one (include the speaker surround).

Its all very well engineered to fit in a small space.

Performance

Well firstly don’t expect it to beat a KX3. But with around 5w on the 80m, 60m, 40m, 30m & 20m bands it is perfectly useful for SOTA operation. This was with a 11.1V LiPo. This drops to around 400mW when using the USB power (which it is clearly not the purpose of that power source)

I’ve not managed to get it out on the fells yet because the weather has been just too bad but I have managed to get a few spots on Reserve Beacon Network on my favourite HF band (30m). OH6BG, SE5E & SM7IUN all picked me up with the 400mW with the loft dipole which works for me. The others were with the full 5W. Including the VE2WU one. Not bad really.

We’ll see how it works in a few weeks time when I get to use it in anger.

Firmware

A quick note about firmware. I don’t think I’ve had an easier experience with these types of rigs. You’ll need to download your copy of the .hex file from the DL2MAN website and just follow the instructions. Excellent

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