Hi Lightspeed,
Yes you can use a car alternator; if you can spin it fast enough! - so best used on a combustion engine generator, unless you modify the alternator with permanent rare earth magnets - expensive!
How about making a generator from scratch and bespoke to your needs? Enter...
http://www.energy-creator.com/the-coil.php
I bought this guys video and highly commend it.
It explains how to make a powerful generator that creates power even from a low rpm - unlike the car alternator.
Using plain and simple tools, the generator is very easy to make and is quite novel!
See his videos!!
For more info on different electric generators, see link below
http://www.otherpower.com/otherpower_win...ators.html
Hopefully something like this (see earlier post) could help with our comms or power needs; now, in the field or post 'doo-doo hits the turbine'.
Cheers Juice.