English: A Russian MI-189W magnetron tube from an obsolete aircraft radar. It generates a pulsed output at 9 GHz in the X band. The end of the tube with filament contacts projects inside the red pipe at right. The rest of the tube itself is concealed between the two powerful horseshoe-shaped alnico magnets that provide the magnetic field it requires to operate. The pole pieces of the magnets embrace each end of the tube, creating a magnetic field along the tubes axis. The microwaves produced radiate out of the rectangular waveguide aperture at top, which in use is attached to a waveguide which conducts the microwaves to the antenna. The text on the front side reads: "Do not bring ferromagnetic materials closer than 100 millimeters".