) writes:
Henry Kolesnik wrote:
I sure see lots of retired cell phones and wonder why I haven't seen any
homebrew projcts to make something useful out of old outdated ones.

It always surprises me how little useful I can get out of these. I
used half the diplexer from a big old one as a filter for an 875 MHz
local oscillator chain for a 903 MHz receiving converter. And I used
the speaker from a more modern one to provide sidetone for a laser MCW
transmitter. That's it so far....

The big clunky ones, and I've not seen any at garage sales in a few
years, have offered up things like FM IF strips (they've tended to
be really easy to isolate from the rest of the unit), various crystal
filters with centre frequencies above 30MHz which would be suitable
as roofing filters, some txcos, go back far enough and they have
standalone NE570 (or later variants) compander ICs. I've also pulled
prescaler ICs out of them.

The trick is that the older and bigger they are, the better the parts.
There will be recognizeable parts, and many will even be in DIP packages.

The more recent they are, the less valuable because everthing gets
highly integrated. I opened one hand held cellphone, of recent
vintage obviously, and the IF filter was barely recognizeable.

Because they were specifically designed to be part of a system (ie
you'll never use a cellphone by itself), they have usually been
way too dedicated to allow for much in the way of modification.

MIchael VE2BVW