#electronics .
I want to use a coil to send low-speed data across an air gap (rotary transformer).
Searching the web, it looks like I'm the first one with this idea.
5V, low power sender, 20Hz times 2 bytes. 2-5 cm diameter, 5mm gap.
I know I need to drive it with AC (FM?), but how do I receive? Band-pass filter? How do I wind the coils to be sensitive enough?