Waveguide of a microwave

A waveguide, is a hollow rectangular tube, designed to channel microwaves from the Magnetron to the outside world.

Rather than use a wire, this is found to be the best way to transfer microwaves at 3 cm to 10cm wavelength. (Some 10cm systems use large coax instead)

They are normally found on radar systems, to transfer the signal to and from the rotating scanner to the transceiver unit.

Modern radars keep the length of the waveguide to a minimum, by housing the transceiver in the motor unit of the scanner, instead of a separate room.