i thought about using a transistor instead. I hoped that I could bypass the switch with a transistor ? Is that possible ?
Yes it is but you need to know what voltage the switch has on it. As it is a radio it is very unlikely to be 5V. The point about using a PNP transistor as a top switch like this, is that the signal you put on the base of the transistor needs to be as big as the voltage you are switching. If it is not then then you need another transistor, an NPN one to boost the 5V signal from the Arduino to the voltage you are trying to switch.