The mixer stage acts like two traditional direct conversion mixers operating in tandem. It centres around U10, a SOIC-16 Dual 4:1 Mux/Demux Bus Switch. A 2-pin and 3-pin socket also needed to be installed along with three resisters. And for testing the stage, an 80/40m Band Pass Filter board also needed to be built.
Care had to be taken once more when soldering the tiny pins of U10 into position.
Building the BPF was relatively simple, with the exception of winding the two coils; these take time and care but aren’t particularly difficult to do.
Testing went well. Current and voltage readings were as expected. The only test I was unable to carry out at this stage was to test it with Rocky, a SDR software package that shows a chunk of spectrum. This was due to my Linux laptop’s sound card not showing up in Rocky.
Next will be to build the TX Op Amps.