I finally landed at a quiet tape vs. noise configuration for TouCans on Saturday afternoon. Here’s how. In the picture above, the wires circled in green include the + and - power wire, (white and red respectively), and the keyer wire, (also red.) When I taped the bundle of wires including the single turn coil shown in the white wire to the side of the can, the noise from the power supply went away. I was left with only noise from the radio, (the kind I want), and a gentle hum from the power supply because it had switched into buck converter mode to step its voltage up to the required 15V! The helicoptering from the Pico-W was also almost gone. In other parts of the project, the Pico-W has started burning through pairs of AA batteries rather quickly.