The Power Supply.

If you use a mobile or hand held type of radio as a base, you will need one of these to convert the mains supply to 12volts for the radio.


For a legal CB, the power supply will need to have:

* mains voltage input.
* 12 to 14volts DC output.
* 2Amp (or more) output current.
* Regulated output


* Model Train power supplies.
* Multiple output transformers. The ones where the box plugs into the mains socket, and the output leads come straight from that box. Some may have variable output voltage, some don't.
* Battery chargers.

Any of the above will NOT have a regulated output and may even have a certain amount of AC in the output. At best, they will make your outgoing signal bad (with a loud buzzing sound), at worst they will destroy the radio.
Another type of supply to avoid is the Switched Mode type. These are commonly found in computers, and are used due to their efficiency. Unfortunately, they can interfere with radio equipment - with noise on the power line or radiated from within the case.