cd/radio looses preset stations?

i have a peugeot 307 that has a none genuine cd/radio fitted but it will not keep the preset that i enter if i set the stations before i go on a jurney they store ok but when i stop the car and turn the ignition off the next time i come to use the car all the preset stations have been lost its as though the reset button has been pressed i bought a new cd/radio but it does the same. any settings that i put in are all lost.