Heath Company

Donald L Hornback

A microprocessor-controlled antenna positioning system for automatically steering a rotatable antenna in the direction of a source of radiated signals is disclosed. The present invention, which is particularly adapted for use in a television receiver or a subscription television receiver (STV) decoder, automatically seeks the best signal when a new channel or frequency is selected, remembers that preferred antenna position, and will return to it whenever that channel or frequency is subsequently selected. A large number of desired antenna headings may be stored in memory for subsequent use and the computer-selected antenna heading may be modified to avoid TV ghosts or to select a second station on the same channel. The system determines optimum antenna direction by sweeping the antenna through a full 360.degree. circle, keeping track of the width of receivable signal lobes. Upon completing the sweep, it selects the widest transmitted signal lobe at the desired frequency and positions the antenna in the center of that lobe. In addition, an intermediate frequency automatic gain control (IFAGC) voltage representing received signal strength is compared with a predetermined signal level established by the viewer for insuring that received signal strength is sufficient for presentation of a minimally acceptable video image. Accurate positioning is insured by incrementally rotationally displacing the receiving antenna, sequentially and repetitively comparing the new position with a programmed, or stored, position by means of a control signal feedback loop, and generating antenna positioning commands in response thereto.

Automatic antenna positioning system

A system for stabilizing the synchronization (sync) signal provided to a second video display generating a second video signal for the precise overlay thereon of a first video signal from a first video display having a relatively unstable sync signal is disclosed. The stable sync signal is generated by providing the multiplied unstable sync signal to a phase lock loop synthesizer in generating a higher multiple frequency signal which is synchronous with and phase locked with a sync signal of the first video signal and has a frequency which is an integral multiple of the horizontal active line period. The frequency of this signal is an integral multiple of the number of pixels, or dots, per active horizontal scan line of the second video display. By synchronizing the horizontal scan signal of a second video display with this high frequency signal, an integral number of pixels per horizontal scan line is provided. The synthesized, stable horizontal sync signal is then combined with a stable vertical sync signal to form a stable composite sync signal which is provided to the second video display permitting the synchronized overlay thereon of video signals from both video displays.

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St. Joseph, MI, United States of America

Donald L Hornback