The NE602 was an old part. The product was bought by another company
(Signetics?) who renamed it SA602, but kept the rights to the name NE602 so
sometimes you still find an NE602. Worse yet, the NE/SA 612 is a little
more widely available and somewhat cheaper -- sometimes a lot cheaper. It
is the same part with a little different set of QC tests, so for any
imaginable application, all 4 parts are the same thing. If you were doing
some military application there might be a slight advantage to the 602 over
the 612, but even that isn't clear from the spec sheets. Usually (but not
always) if you find an NE part it will be "old stock". Sometimes the 602
will be a few cents more than a 612, other times it will be 2 or 3 times the
price, although it's only a couple buck part so paying double isn't going to
break the bank, anyway.

The NE602 was widely used in a lot of projects, and still is. Hams got used
to calling it an NE602 so the name stuck, even though an actual NE602 is
hard to find anymore and the alternatives at least as good. Guys who build
lots of receivers have a drawer marked NE602 that probably contains more
SA612's than NE602's.

...

"Andy Bullington" wrote in message
news
I'm really interested in building the product detector and second and
third mixers for my R4C as described in the recent QEX article. My
question is (and please pardon my ignorance) in 2 places an SN 602 IC is
called for but I can find no trace of such a component anywhere. Is the SA
602 or NE 602 the same? I'm a ham but a musician by trade and learning
this stuff as I go. Thanks in advance.
Andy W1AWB