- I've built keyers with optoisolators and also just with FETs and never had a
problem with either method.
- Regarding audio transformers: I built my original so2r headphone switch
without one and had constant buzz in audio from one of the rigs. I added one
transformer (on the audio from the left rig) to allow isolating the grounds
between rigs and it silenced the buzz. I used a 1:1 audio transfromer from
local electronics store with no mfr. or part number markings.
CQ-Contest mailing list