First of all, superhet receivers have only one stage of detection
and filtering, not two, after the last IF stage, right?

Wrong. The conversion of the RF signal to the intermediate frequency is a
form of detection (ie, non-linear mixing). The IF stages provide filtering
that removes the unwanted components of the mixing process.


o Is their explanation of how DCR works even correct? I don't
understand the business of mixing the signal with a LO signal:
why would you do that?

Ever heard of a product detector?


Anyhow, I think I've shown that even if I'm way off base, Wikipedia
articles tend to be extremely badly written, if not outright full of
doubtful information.

Badly written, yes. Some articles need a thorough re-write.

Doubtful information? I don't think so. In areas I'm knowledgeable about, I
find Wikipedia remarkably accurate.


What else would one expect of the "encyclopedia" that
any PlayStation-playing, junk-food wolfing pimple-faced
junior-high-school student can edit?

What kind of useful criticism can we expect from someone who doesn't seem to
know much about receiver design?


By the way, the last "GE Transistor Manual" had a classic "direct
conversion" (???) FM tuner (p385) that had only one inductor and no bandpass
filters. (45 years later, I still don't understand how it works.) I'd wanted
to build it, but the transistors were expensive -- the parts came to close
to $100.