Usually the DC power jack on the side of the radio has a built in "switch" which disconnects the battery when the AC adapter is plugged into the radio.
hmmm...simple yet straightforward solution now that you've mentioned it...thks!
To complicate the matter a little, what if i now hv a usb port on the microchip (eg 18F4550). What can one do to hv the uC system to, say, switch off, the battery or the ac adapter power and use the usb power that comes on from the PC.