Antenna

A marine satellite television receiver antenna system for use on a marine vessel, comprising:

• a receiver antenna having a main reception direction, the receiver antenna comprising a rotatable components,
• means for rotating said rotatable component so as to rotate said main reception direction in a conical scan,
• means for scanning the main reception direction of the receiver antenna,
• means for measuring the signal strength of a signal received from the antenna during a scan to produce a measurement signal, said means for measuring including sampling means for sampling the signal received by said antenna at spaced points in said scan to produce signal samples and for generating said measurement signal in dependence upon a difference between said signal samples from different said spaced points, and
• means for varying the alignment of the antenna to maintain orientation with a satellite based on the measurement signal.

A satellite television receiver antenna system comprising:

• a receiver antenna having a main reception direction, said receiver antenna comprising a rotatable component for scanning the main reception direction of the receiver antenna at a scan rate,
• means for measuring a signal strength of a signal received from the antenna during a scan to produce a measurement signal,
• means for varying the alignment of the antenna to maintain orientation with a satellite based on the measurement signal, and
• scan rate control means for maintaining the scan rate, said scan rate control means comprising sensor means responsive to a rotational position of said rotatable component for producing a sensor signal, and rotating means for rotating said rotatable component in dependence upon said sensor signal to maintain said scan rate substantially constant, said rotating means comprising a motor, a pulse controlled power supply and supply means for supplying power control pulses to said pulse controlled power supply, said supply means comprising means for deriving, from the sensor signal of the sensor means, at least one pulse within each rotation of said rotatable component having a width which increases in dependence upon a rotary period of said rotatable component, so as to increase the power supplied when rotary speed of said rotatable component decreases.

A satellite television receiver antenna system for use on a vehicle, comprising:

• a receiver antenna having a main reception direction, the receiver antenna comprising a rotatable component,
• means for rotating said rotatable component so as to rotate said main reception direction in a conical scan,
• rotary position detecting means for sensing first positions of said rotatable component,
• sampling means for sampling a signal received by said antenna at spaced points in said scan to produce signal samples, and
• interpolation means responsive to said rotary position detecting means to produce a plurality of sampling position signals corresponding to said spaced points at second positions between said first positions.