I’ve been building a QMX+ HF QRP radio from QRP Labs since a little before Christmas. It’s finally completed and ready to go!

I’m pretty happy with it. It’s a kit build designed by Hans Summers (G0UPL) and has a bit of a cult following online. The latest version does SSB as well as CW and data. What interests me most are the small size and built in WSPR beacon.

I opted for the QMX+ rather than it’s smaller cousin the QMX as there is plenty of space inside the radio to add some personal touches. In my case I wanted to add a battery pack to make the radio truly portable.

In terms of performance I get around 2.5 – 3w measured output power across the HF range which seems to be around what most people achieve. There are a few compromises in the design I suspect to reduce the radios size such as sharing toriods across more than one band in the filters which I think likely mean that it is tricky to achieve the full specified 5w output power. Possibly with some more fiddling with the number of turns in each inductor it may be possible to optimise for increased power output but to be honest it’s not likely to make that much difference. I experimented with squeezing and expanding the turns on the toroids with limited success.

For the battery pack I used the design here from TA7MNA. Originally I intended to purchase the custom made board to do the job, however, unfortunately Mustafa has stopped producing the boards and although the plans are freely available on his GitHub I couldn’t find someone to produced them cheaply for me. Therefore I painstaking re-constructed the design on prototyping board! If I did this again I would purchase the expansion board from QRP Labs which would make this much easier. I didn’t include the audio part of the project as I plan to use a Retevis hk008 amplified speaker microphone for SSB use which I think will be a more practical solution.

Now I just need to learn CW to do it justice!