ozQRP MST400

Here are some (very poor quality) photos of the current project. An ozQRP, MST400 the MST standing for “Minimalist Sideband Transceiver”. Available as a partial kit in two versions, 40m and 80m. I’m building the 40m version designated MST400. The kit comes with the PCB and optionally some hard to find parts. You source the rest of the parts yourself. The parts sourcing issue elevates this kit to an intermediate level of difficulty. This is not a beginners kit.


Front view. Plastic box (finding good, cheap metal boxes is so hard – sigh). Metal front and rear plates. Silver knobs from a very old defunct crystal CB radio (Yeah, I know, never use metal knobs!). The fact that the two smaller knobs don’t line up properly shows up in the photo! It’s not so noticeable when your holding the radio. I’ll have to do something about that. The misalignment is due to the way I mounted the pots (more on that in a minute). The signal strength meter is from the same discarded CB radio.


Top view. Speaker grill is a sink drain filter. Not sure if I like the look or not. But it’s functional. Next time I might just use it as a template and drill holes in the plastic. The construction manual is alongside. The manual is absolutely excellent! Not quite the Elecraft “step-by-step” gold standard but very good for the intended audience.


I had a roll of aluminium foil (flashing) with adhesive backing. Available from hardware stores and used for insulation. I used it to insulate the box from RF. I mounted the DDS VFO, a separate but matching kit (you can supply your own VFO if you prefer) and the controls to a PCB set rearwards from the front panel. Rather than mounting them directly to the front panel. This makes it easier to keep the front panel looking neat and builds a RF shield between the DDS VFO and the main transceiver PCB. Probably not required but it seemed like a good idea.


Another shot of the case top cover. Showing speaker, sink drain speaker grill and aluminium insulation.


Front panel and DDS control board. Upside down. Not only can I not take in-focus pictures I get them upside down as well! I’ll fix it later.


Here is the cause of the pot alignment problem. Because of the pot shaft length that I had on hand I decided to try and solder the pot body directly to the PCB. It works. But the precise alignment is quite difficult without building an alignment jig to hold the pots in place while soldering. And if you build that jig, out of say PCB material, then you may as well make it permanent! Ah, well, live and learn.