When I wanted to build a diplexer, I read that this can be done by using a highpass anda lowpass filter. But what if someone wants to make a multiplexer, or if one wants to use bandpass filters? As I recently needed to make a small diplexer, I decided to make a little writeup of my process.

Because the ordinary bandpass filters have a 50 Ohms input impedance, it is not possible to directly connect two filters to the same source, because the input impedance of one filter would disturb the other filter.