My understanding of the FM capture effect is that if an FM receiver receives two, on frequency signals, it suppresses the weaker one and demodulates the stronger one, given that the difference in signal strength is significant enough. This differs from the case of AM where the two signals are summed together at the receiver. I don't understand how the capture effect work. I've tried working it out mathematically, and in block diagram form, but I still don't understand the phenomenon. Can anyone explain what causes the capture effect? Also I've read that the capture effect occurs with all angular modulated signals; i.e. FM, PM, PSK, QPSK, QAM, etc. From what I remember from my communications course, when demodulating PSK, QPSK, and QAM, the receiver decomposes the signals into an I and Q signal, and they are individually demodulated using AM like techniques. So, is it accurate that the capture effect is present with these types of modulation schemes? Thanks!