Abstract: An antenna structure has a rotatable dipole array constituting a driven antenna element, a cup mounted around the dipole, a first conductor connected to and extending from the antenna, and a first dielectric mounted around the first conductor. A second conductor is mounted around the first dielectric, and a second dielectric is mounted around the second conductor. A third conductor is mounted around the second dielectric, and the first and second conductors form a quarter-wavelength transformer. The first dielectric maintains a uniform spacing between the first and second conductors, and the third conductor defines a radio-frequency coupling cavity. The second dielectric electrically enlarges the cavity. Thus the physical dimensions of the structure can be reduced without sacrifice of its electrical properties.

Abstract: Signal propagation apparatus is formed with a waveguide cavity for propagating first and second electromagnetic signals respectively having first and second electric fields that are distinguished outside the cavity by first and second polarizations, for example orthogonal polarizations, one vertical and one horizontal. Within the cavity, the electric field lines are curved and cross one another at angles that vary as a function of location within the cavity. A pair of probes are mounted within the cavity in spaced-apart relation to each other and have orientations that differ from the orientations of the electric fields outside the cavity. In order to send or transmit signals having electric fields that are respectively vertically and horizontally polarized, for example, thereby forming an angle of 90.degree. with respect to each other, the probes lie in planes forming a dihedral angle of about 80.degree..

Abstract: A dual band signal receiver is provided with inner and outer relatively coaxial cylindrical waveguides electromagnetically coupled to respective upper and lower band rectangular waveguides and ports through suitable polarization switching probe assemblies. The rectangular waveguides are mounted adjacent one end of the outer cylindrical waveguide. The rotatable probe assembly of the inner cylindrical waveguide is electromagnetically coupled to the high band rectangular waveguide by a suitable transmission line extending substantially along the longitudinal axis or centerline of the outer cylindrical waveguide.

Abstract: An electrically-conductive flexible probe is mounted within a wave guide that receives radio-frequency electromagnetic radiation. A leading portion of the probe has an orientation that is adjustable between two positions that are angularly displaced with respect to each other by 90.degree.. A permanent bar magnet is connected to the leading portion of probe, and an electromagnet is mounted adjacent to the bar magnet so as to be capable of being magnetically coupled to the bar magnet.

Abstract: Disclosed is apparatus for and a method of continuously filtering and optionally degassing molten copper and otherwise extracting impurities therefrom comprising disposable porous ceramic foam filtering means and means for supplying a deoxidizing or cleaning gas advantageously disposed within a chamber containing a flowing stream of molten copper.