"Harry - SM0VPO" ) writes:

As stated, the basic problem is getting a chip that is available, cheap and
is likely to be available next year. The MB501 (SA701, MC12022, SP8704) is
now classed as "obsolete" and one of my sources has also dried up. By the
way, the TDA7000 is also obsolete and is soon to be joining the ZN414/5/6
and TCM3105 chips in the depths of obscurity.

BR Harry - SM0VPO


Do they have really cheap FM broadcast band only pocket radios over there,
that tune with one button (and have a second button to reset to the bottom of
the band)?

They're everywhere here, and I've seen them for as low as $1.99 Canadian.
Curious, I bought one at that price. No cermic filter, so it's using
an oddball scheme. My first thought was that it was a TDA7000; as I
mentioned a couple of weeks ago, the number on the IC was barely visible.
So I looked up the TDA7000 on the web (it was easier than digging out
the paper datasheet), and clearly it was not a match. But Signetics
had pointers to a couple of other similar ICs, ie converting down to
70KHz where active filters can be used, and that frequency locked loop
scheme. One of them was a match, if I'm remembering a 7088.

I don't know how the specs generally compare with the TDA7000, but
this IC has the logic in place for the two button tuning scheme.
Obviously these are being put into products (I always wondered if
the TDA7000 actually was put into commercial products), and hence there
is an available source. Maybe not as IC, but the cheap radio is there.
The IC is surface mount, but it's already soldered to a circuit board.
Change the required parts, and you've got the radio or IF strip.

Michael VE2BVW