One of my goals for 2024 was an electronics “Wildcard” where I would finish my QDX transceiver kit or some other ham related project. Today I will mark this one complete, as I finally got my QRPLabs QMX Multimode Transceiver on the air and completed a couple of FT8 contacts.
I did have a few glitches trying to get the rig on the air using WSJT-X (version 2.70 rc6). The first had to do with the short USB-C cable that came with the kit. When I tried using that, I received a pop-up message saying the USB device was unrecognized and had failed. Several folks said they had issues until they changed the USB cable, which I did, and that appeared to work just fine – COM 6 came alive.
The next issue had to do with setting the rig in WSJT-X. The manual suggested “TS-440”, which was a choice that appeared as “TS-440S”. However that did not work, and returned a pretty long failure message when I tried to the Test CAT function. The manual also suggested “TS-480”, which did appear as exactly that (no “S” at the end). That fixed the issues and WSJT-X was now in control of the QMX.
A few minutes later at 1842 UTC I responded to CQ POTA N0WHA EM91 who was -04, and received a -15 in return. At 18:48 UTC I responded to CQ POTA N4NR EM64, who was +04. I did receive a -14 report and a 73 in return. Both stations confirmed the contacts in their POTA Activator logs. So the QMX is working.
In the photo below, you can see the QMX attached to an Elecraft T1 QRP Antenna Tuner, and if you look closely you can see a 3dB attenuator installed in line with the QMX. The QMX lacks a tuner, and if it detects a high SWR, will immediately shut down the transmitter. This quick response prevents the T1 from being able to do its job. By inserting a 3dB attenuator, that guarantees no matter what the antenna load, the worst case SWR seen by the QMX is less than 3:1 – a value that no longer cuts out the transmitter. When the T1 is tuned correctly, the 3dB attenuator can be removed. If you leave it in, the 5 watt output of the QMX is reduced to 2.5 watts. 3dB of RX attenuation really doesn’t matter on the receive side.
In the photo below, you will see the exchanges with N4NR as well as the waterfall.
