"chickenhawk" ) writes:
Typically a phase locked loop (PLL) oscillator driven off of a crystal
oscillator running as a frequency useful to other housekeeping functions in
the phone. All of this is usually done in custome IC hardware by the major
manufacturers.


But by the time you see custom ICs, everything is pretty small and there
is much less likelihood of being able to recycle any of it. I paid fifty
cents for a relatively recent handheld cellphone last summer, and I could
barely identify the crystal filter, and it was pretty much a waste of
the money since virtually nothing could be reused.

Older ones are a different matter. The big clunky portables, the mobile
units from the early days. In those, most of the ICs are identifiable,
and even in DIP packages. I've seen common Motorola synthesizer ICs used.

These old phones are a neat source of parts, particularly since nobody
wants to use them anymore (or they outright can't be used anymore), so
the cost is low. Pull out a temperature compensated crystal oscillator, a
nice FM IF strip with a crystal filter in the 45MHz or higher range (plus a
crystal to move it down to 455KHz), prescaler ICs, those synthesizer ICs,
various computer stuff (the old ones have things like 8085s, and their
peripheral ICs), and NE570 compander ICs.

Michael VE2BVW

larry wrote in message
le.rogers.com...
Greetings
Has anyone taken apart a cell phone or see a block diagram of a typical
cell
phone who could answer a question for me?
I would like to know how they generate the operating frequency?
Larry