Radar start-up time
Why does my radar have to wait 2 minutes after I turn it on before I get a picture?
The component that transmits radar energy is called a magnetron and is similar to that which is in your microwave oven, but much more powerful. This is a tube, which will be damaged if the filament isn't heated to a proper temperature. Therefore, radars have a timing circuit – typically 2 or 3 minutes – which disables the magnetron from transmitting until the filament is sufficiently heated. This protects the magnetron from being damaged.