Building a 40M QCX Transceiver Kit

Introduction to the project

On the lead up to Christmas 2019, my wife asked me if there was anything particular that I wanted as a present. After a bit of head scratching, I decided that I already had enough jumpers to stock a shop, so it was going to have to be a radio related Christmas present this year. But what to ask Santa for ? I had seen reviews on the QRP Labs QCX kit by Hans Summers. This appealed to me as it was available in many HF band versions, it was feature packed and very small. The order was placed for a 60M version. I'm not really sure why I decided on 60M. It must have seemed to be a good idea at the time. Santa duly delivered the kit to me on Christmas night, left in the stocking at the end of the bed, to be eagerly unwrapped in the morning.

Opening the box

I was not disappointed. This was an extremely well produced kit. All components were placed in small plastic bags, grouped together in order of construction. This included the ATMega IC, which is the brains behind the rig, which pre-loaded with the firmware, and the LCD display . For instance, all components for the band pass filter were together in one bag, containing the toroids, capacitors and enameled copper wire.

Although it has two surface mounted ICs, both were already soldered to the board, and the rest of the components are through hole mounted. It is a very small board and the components are close together, so a lot of care is needed to get everything just right. The board itself is screen printed with the position of every component, making it easy to place components in their correct home.

Get soldering

The kit does not contain any instructions. This is quite intentional. The QRP Labs web site has a download section, containing links to the manuals as PDFs for each build revision. They are very comprehensive, running to nearly one hundred and fifty pages. Each page details the installation of one group of components, such as a group of resistors that are of all of one value. Together with the very clear screen printing on the board, construction is pretty foolproof.

The part that is a little tricky is winding and soldering the toroid cores. Their small size doesn't help, but with care most constructors will be able to follow the very clear instructions and get the job done.

As I said in the introduction, my kit was bought with the intention of building the rig for 60M. After more thought, I decided to build it for 40M instead. This was not a big deal, all I had to do was swap the toroids that had been supplied for the band pass filter to slightly different ones, and change the capacitors. Luckily, I had all the parts in stock.

How’s your eyesight?

Mine is okay, but not what it used to be. I have made myself a work station with a built in magnifying glass. I find this essential for any fine detailed work. I also built a small tilted platform to hold PCBs which helps to support the PCB at the correct angle when using the magnifying glass.

Did I mention that this is small? You don’t need anything unusual in the way of tools, so long as you have a fine tipped soldering iron, needle nosed pliers and sharp cutters, you should be ok. There is one essential item that's needed though. A magnifying glass. My workstation has a magnifying glass mounted on a flexible stork, but I use a hand glass as well.

My workstation with the tilted platform. This has a lip along the front edge to stop the board sliding down. The workstation has a built in LED light under the magnifying glass.

You will need some fine tipped tools

Firing it up

So, once you have all the components neatly soldered in their correct places on the PCB, with the board triple checked for solder bridges, or joints with no solder at all,It's time to power it up.

The smoke test, but let's hope we have no smoke today!

So I got to this stage, powered it up and ....... nothing.

The LCD lit up, but that's all. It was at this point that I realised that the ATmega IC was still in its packet, not plugged into its socket on the PCB as it should have been. In my defence, when the LCD is in place, it covers the IC socket, so you can't see it. The IC was quickly inserted, and then we were in business.

The great thing about this kit is that it contains on-board test and alignment equipment. You just need to follow the instructions. It's just a matter of adjusting trimmers in sequence, watching the LCD display as you twiddle. It's really easy to do, and once it's done, it's done. You have a fully functional transceiver.

Putting it in a case.

I think that some constructors just leave this rig as a bare PCB, and use it like that, but I didn’t want to do this. I like things to be a bit more finished off and functional. At one point QRP Labs were able to supply pre-built cases, but I think that the supply dried up, so I was on my own with that one.

What I did have was a second hand diecast aluminium box that I had bought in a job lot from the Chippenham Rally some years ago. I had bought two boxes exactly the same, both containing old projects, both in good condition except for a few holes. I had already used one of them on an 80M DF receiver, but the other was looking for a purpose in life. It was just the right size (maybe a bit of a tight fit). I had to fill the holes, using my baking powder and super glue trick.

I wanted to have the controls on the flat face of the box lid. As the board was designed, the three controls are all at different heights, which would make it very difficult to align with the flat surface of the box, so my circuit board build had to take this into account. I also wanted to move the rotary encoder, the tuning control, to a more central position.

What I decided to do was not to solder the volume control, the rotary encoder or the two press button switches onto the board, but to mount them all on the lid, and connect them via flexible leads. There is a provision on the PCB for you to do this.The height of the board had to be adjusted so that the LCD just poked through the slot that I had cut in the lid for it. I did this by packing the mounting studs with washers to get the height just right. It was a fiddle, but I was pleased with the result. The case was primed with etching primer and sprayed with the remains of a can of car paint my son had used at some time ( Fiat Coral Beige) and the job was complete.

This shows the CW decoder working . DJ6UX calling CQ

This was DJ6UX hoping for a real QSO on a contest weekend. Some chance !

In Conclusion

The only thing that I have changed since building the project is replacing the two push buttons with rather better versions, which are nicer to use and look good too. Sadly, this kit has now been withdrawn by QRP Labs, but it has been replaced by two new kits. They both are built with pretty much the same circuit and the same firmware as the QCX.

The QCX + is just a physically bigger version of the QCX, similar circuit and firmware, but on two boards, one being the front panel, and the other is the main board which is much bigger than that of the original QCX. A very nice case with the front panel screen printed is available as well. If you have dexterity issues (fat fingers) or the eyes refuse to focus like they used to, this could be the answer, as everything is spread out more.

If you like small, like very small, the QCX Mini looks like a winner. This is much smaller than the QCX. Mine in its case measures 12 x 9 x 3 cm, not counting the knobs, but this measures 9.5 x 6.3 x 2.5 cm, and it’s much lighter too. To achieve this, Hans has used a board mainly populated with SMD components, but they are already mounted on the PCB, all done for you, so you just have the ‘through hole’ bits to solder.

I really enjoyed building this kit. You end up with a single band rig, that is truly portable, and gives you a wide range of functions. Maybe it's not ideal for a first project, but if you have had some building experience, it's worth thinking about one of the new versions as your next build.

Contributed by G4SPE

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