Hello all. So I have been trying to build a mixer lately, I have done my research on google but I am still kind of lost. I know now many mixers exist; single diode, multiple diodes, single balanced, double balanced, unbalanced and so on. I don't want to build a circuit blindly, so I am trying to understand what is going on. I stumbled upon this pdf during my search: http://www.carmarthenradioclub.org.uk/mixer design.pdf . Specifically, at the bottom of page 5 of the pdf is a nice little circuit. I thought this would be a nice place for me to start since I have no previous experience with mixers. I have a couple of questions about this circuit, if I may ask... 1) The low pass filter (LPF) will work for a certain frequency of LO, not a range, am I right? 2) How is the LPF attenuating LO from the RF port? I thought freq. of LO < freq. of RF, no? (EDIT: or is this because they are assuming low-side injection?) 3) I have no idea what the job of the IF tuned circuits is. I know if they are tuned to IF freq. then they will have least impedance for IF freq., but what does that do to the circuit? Is it supposed to "attract" the IF signal towards the diode? Thank you. PS: any links, pdfs or sources that you think are good/worthy reads on this topic will be greatly appreciated.