EMI

Spectrum Depends Upon Frequency and Rise/Fall Time

Per hackaday: https://hackaday.com/2024/03/30/how-much-bandwidth-does-cw-really-occupy/ and https://www.youtube.com/watch?v=KEgrTwjWLf0 Ideally a spectrum analyzer will look at both the spectrum and the waveform (oscilloscope), the latter being used for rise/fall time. Also worth noting is the old adage about square waves being made up of sine waves. http://web.archive.org/web/20230711194015/https://www.thepulsar.be/article/generating-sine-wave-from-square-waves/ Of course, rise and fall time is often the highest frequency in your circuit.