@freemo @lupyuen I'm in a funny situation. In my work we use classical EM to make detectors/pickups and kicker magnets etc, but these can be at very low frequencies. For example a couple of years ago, I found an unwanted resonance on a kicker magnet at 6MHz. The PCB I mentioned to you was for phase matching signals from a bunched particle beam at 200 MHz. At very low frequencies (~100 kHz) fields leak through conductors, which can also a potential concern for me. It feels a world away from typical modern RF/electrical engineering, but clearly there is overlap. I'm always interested to read your EE posts :)