Not quite sure i'm with you on that one.

On a radio you have 2 lives and an earth. One live is permanent and one is switched. The permanent is there to keep the unit always powered on, if not you would loose your radio station presets and your bass / treble settings etc everytime you turn it off. The switched live dos just that, switches it on and off.

The aerial does the same thing, 2 lives and an earth, so when the switched live turns off, the aerial still has power from the permanent live so it can wind itself down.