Automatic tuning circuit for TV receiver - approaches wanted station from both directions at progressively reducing tuning speeds

摘要

The automatic tuning circuit is designed for use in a TV receiver. It has a circuit to control coarse and fine tuning. The control circuit generates a relatively fast sweep signal for coarse tuning and a slower one for fine tuning. The changeover from coarse to fine occurs when the wanted frequency is first detected. The circuit then fine tunes backwards towards the wanted station. When the wanted station is again detected fine tuning reverses again to move forwards but at a lower speed. This approach is repeated a fourth time before terminating.