Abstract: An antenna and preamplifier system suitable for use with airborne ADF equipment. Each of two orthogonally oriented loop antennas feed a different one of two preamplifiers. Each preamplifier includes an impedance establishing network and a pair of negative feedback amplifiers operating in push-pull.

Abstract: A playback system for recovering prerecorded information from a disc record through the use of a stylus mounted on a stylus arm includes a stylus arm lifting-lowering device. The lifting-lowering device uses a permanent magnet mounted on a leaf spring. The permanent magnet is arranged to normally occupy the central volume of a core with a coil wrapped around the core. The leaf spring has an extension to receive the stylus arm. When an appropriate control signal is applied to the coil, a magnetic field is generated which tends to repell the magnet out of the central volume and the stylus arm, which rests on the extension, is gently lowered toward the record.

Abstract: In a system where improvement of the signal-to-noise ratio for a wideband video signal is effected by subtraction therefrom of a signal which follows low-amplitude excursions, within selected close-to-axis limits, of the video signal's high frequency component, means are provided for varying the selected close-to-axis limits in response to variations in the level of noise accompanying the video signal. In an illustrative use, the noise reduction apparatus is advantageously employed to process a luminance signal component separated by the comb filtering from a composite signal recovered during playback of a video disc, with the limits varying means being responsive to variations in the level of noise accompanying the luminance signal components. The subtraction step is effected in apparatus also serving to recombine separated luminance and chrominance components for formation of the disc player's output composite signal.