D Peter Maus ) writes:

There is a chip...I forget the designator...but it replaces the ZN414
family....an AM TRF on a single chip, running off a single AA cell. It
will run a month, non stop, on a single cell.

I'm pretty sure it's the MK484, though I can't remember who makes it, and
I've enver seen a good explantion of how it differs from the ZN414 (I assume
there must be some slight difference, or else the company might as well
have just second sourced the '414).

It works so well by having good AGC action, so you get lots of gain between
stations, and then when you're tuned to a station the AGC kicks in and makes
the single coil appear to have far better selectivity.

THe ZN414 came out in the early seventies, and obviously someone decided
there was enough demand to bring out the MK484. Yet in all this time,
I've never seen them actually used in a commercial device. Lots of hobby
circuits, and someone must be using them, but I've never seen them.

When tracking down the IC used in those $1.00 FM radios with the "scan"
and "reset" buttons, one schematic showed an AM section, using the MK484.
ANd that would make sense since it makes an AM receiver comparable with
the FM section, yet all I see are cheap FM only receivers.

Michael