1. The problem statement, all variables and given/known data I am doing a project on the Elenco AM/FM superheterodyne radio kit. I have been stuck for ages trying to figure out how the two common emitter amplifiers are tuned to filter out anything that is not around 455 kHz. I tried to find a bandpass filter, or a high-pass and a low-pass filter, but to no avail. Here's the entire circuit for the radio kit. I am interested in the AM part of the circuit (the lower part). 2. Equations Not any for now... 3. The attempt at a solution I know that transistors Q8 and Q9 form two common emitter amplifiers. I think that the capacitors C34 and C36 might have something to do with the selectivity of the amplifiers. Transformer T7 could be playing a role in it as well, I have no idea. What I do know is that the instructions that came with the kit say the following: To be honest, as a beginner, I don't understand all of what is explained. I do understand that T7 is probably the most important component to provide selectivity. That is all I know. Please, can someone help me figure out how the amplifiers are setup to filter anything but frequencies around 455 kHz?