QRP Labs QMX SSB beta firmware relased

Tl;dr: yes, but it is really only intended for amateur use.

QMX(+) can technically tune anywhere, you can go into the configuration and adjust the band RF ranges so you have full control over what frequencies the QMX(+) will attempt to tune. These configurations are there so a law abiding ham can keep themselves from making the silly (and illegal) mistake of transmitting out of band.

But it has band pass filters around the ham bands, so you’ll lose sensitivity the further you get from a ham band in general. There would be some places where you wouldn’t lose sensitivity- the 10m and 12m band use the same filter, so you would get full sensitivity between 25-28 MHz. As far as I’m aware you must select a band pass filter and cannot bypass without a hardware mod (I honestly wouldn’t be surprised if Hans put in a bypass for diagnostic purposes but I don’t know). There is almost certainly a way for you to make one of the band pass filters very wide, but this would be a substantial modification, requiring you to figure out the inductance values yourself.

On the Tx side the issue is low pass filters. You can configure which filter bank gets used, so you could configure it to transmit on any frequency. But the filters are designed specifically to keep the the transmissions clean and legal- there are certainly frequencies where you would have to select a low pass filter that does not suppress a harmonic to legal levels.

Footnote: the 160m band has issues on the QMX+ but I’m pretty sure that will get fixed in another firmware release. But for now the useable range is ~3.5-54 MHz and not all the way down to 1.5 MHz.

If it's anything like the PE1NNZ uSDX/derivatives it tunes only in the (rough) ham bands - obviously if you modify the firmware to remove the end limits of the ham band you can tune to other frequencies but fundamentally, the thing has a bunch of relays and coils for the different bands.

Only the ham bands, and there are three different models that hit different harmonics of the bands: 80/60/40/30/20m; 60/40/30/20/17/15m; and 20/17/15/12/11/10m.

Maybe earth shattering isn’t the right word, but this is a big deal for fans of QRP labs. The (tr)usdx is a bit cheaper hardware, which limits the performance. The QMX has a more powerful processor and will outperform the (tr)usdx by several dB in terms of distortion.

Hans (the designer) is an amazing developer and very thorough, and his kits are very high quality. He includes several diagnostic tools in his firmware, so you don’t just build a kit, but you can diagnose and tune the performance with the kit itself. A beta release from Hans is practically a release candidate in everyone else’s eyes because he’s so thorough.

In terms of functionality, this SSB mode means you can do practically any modulation now, where previously you could only do single frequency fixed amplitude modes. So now you can do PSK, winlink, SSB voice, and whatever modes become popular in the future.

Hans took a while developing this because he wanted to get the max performance from the tiny ~5W transmit power, so he implemented a technique called controlled envelope SSB which was clearly challenging to get right, and I’m not sure the (tr)usdx even has the processing power to implement it.

I’ll probably buy another kit because of this just because I’m so excited (I built a QMX+ last year). This makes the QMX a really good radio. It has always been high quality, it was just held back by only being able to do CW and a certain digital modes. Being able to do voice and ALL digital modes at this price range and quality is unbeatable.

I can't say for sure, but I think you're going to start to struggle with performance and I wouldn't want to spend a lot of effort on it.

It is already a challenging to get good 6m performance from the QMX+. You would have to redesign the filters for 4/5m and you might still get poor performance due to being close to the limit of the si5351 chip (the frequency source), as well as the fact that parasitic capacitance on the PCB is going to start to matter. You might also have to modify the firmware, so it might end up being a lot of effort for the modification.

did it work?