ACØPR, ham radio blog: Building a 40m QCX Mini to go with my 20m radio

After a couple of SOTA activations using my 20m QCX Mini, I started feeling guilty about completely leaving out the many great 40m chasers I usually have. I decided I needed a second QCX Mini for 40m. It would also be good to have a backup radio in case one fails. I haven't checked to see the weight difference between two QCX Mini radios and the HB-1B, but I'll do that soon. Also, my 20m dipole won't do the trick for 40m, so I'll look into my antenna setup as well.

I was excited to get the package--coming all the way from Turkey. It wasn't long comparatively. I received it in the evening of a work day so decided I would divide the build into two nights after work. I also documented this build more than the first one. Having done one before, it went a little faster this time. All the toroids had more windings though (required for the new band).

I ran into my first snag very early. I had the main toroid done with the four different windings (a little complicated), and as I was getting all the wires in the right hole, I tugged on one too hard and it broke. So, either make it work or re-do the windings. However, this was the longest portion and it was already cut to solder in place, meaning I may not have enough wire to wind it again. I decided to just make it work and use the "stub" of wire left. It took some doing, but got it soldered and in place. This time instead of trying to burn off the enamel coating on the wire to make the electrical connection, I scraped the enamel off as I have in builds in the past (spoiler--it totally worked the first time).

The placement of components went smoothly and although I followed the instructions carefully again, I didn't feel the need to read them numerous times and was more confident. Everything went smoothly after the first toroid issue. Before too long I was connecting the different boards together. At that point, the soldering was done and it was time for the smoke test. It always make me nervous, mostly because in the years I've been building I have had two failed smoke tests--each time a capacitor burned out and there was indeed smoke.

I hooked up the power, and low and behold, it turned on as it was supposed to. I was pretty excited. I went through the preliminary setup and tests and adjustments. Once those are all done, the radio is actually ready to use and be put in the case. This is the point when I had all the parts hooked up and tested the wattage. My 20m radio had an original output of .7 watts and after lots of tweaking and reading (and trying to fix the poor toroid connections) I finally got it to 4.4 watts. This time I hooked up the watt meter and it read 7.3 watts! Now that's with a dummy load though, I would need to test it with an actual antenna.

With the preliminary tests done, it was time to put the radio in its case. The first try didn't quite fit, even with some wiggling. I did see where the issue was though, and I knew I needed to just file the board in a spot. After doing that, it went right together and the project was done! I hadn't checked the receive on it yet, so I connected to my shacks main antenna and starting listening and found numerous stations and activity on the band. I checked the wattage again now that I was using a real antenna, still 5.5 watts--outstanding and just where it needed to be.

Next will be a test in the field, once I've modified my antenna system. I'm most like going to just clip on extenders on the end of my 20m dipole using 30 gauge wire (extremely thin). I just need to tune the extenders so my SWR is good. Hopefully this Saturday I'll be able to test it out for real.