We often use the term “power supply” to denote a piece of equipment that will process the electrical power from a source, such as the ac power mains, by manipulating it so the device output will be acceptable to other equipment we want to power. The common form of the power supply is the familiar direct-current power supply, which will power a transmitter, receiver, or other of a wide variety of electronic devices. Often a topic of discussion among hams, power supplies are required by almost every type of consumer and Amateur electronic device you’ll likely encounter in a home or shack. They often make great homebrew projects, especially for beginners.
In the strictest terms, however, the power supply is not actually a source, or “supply” of power, but is actually a processor of already existing energy. Therefore, the old term “power supply” is becoming obsolete, and a new term has arisen to refer to the technology of the processing of electrical power: “power conditioning .” By contrast, the term “power supply” is now used to refer to devices for chemical to electrical energy conversion (batteries) or mechanical to electrical conversion (generators). Other more exotic varieties include thermoelectric generators (TEGs) and radioactive thermoelectric generators (RTGs).