Diodes used for "mixing" - why needed? At the site http://www.st-andrews.ac.uk/~www_pa/...rt1/page1.html [Broken] there is a very comprehensive explaination of a "mixer diode". My question: if the diode is always forward biassed to produce an output frequency of fs - fl (source minus local frequency), why is the diode even needed? Would not this same circuit without the diode produce the same strong "beat" at the source minus local frequency? Thanks from someone pretty confused about this.