It's not that modern receivers are more sensitive, but that they are more selective. Harmonic or "image" rejection can achieve 20 to 60 dB in commercial applic

It's not that modern receivers are more sensitive, but that they are more selective. Harmonic or "image" rejection can achieve 20 to 60 dB in commercial applications today. The first and last sections of this paper may help explain: http://www.plextekrfi.com/images/pdfs/RF_mixer_design.pdf http://www.plextekrfi.com/images/pdfs/RF_mixer_design.pdf