| 摘要 |
<p>PURPOSE: To prevent noise by incrementing or decrementing a tuning frequency fo by one step each, receiving a normal signal after stop depending a change in H, L so as to reduce the reception time in the HRC mode when an AFT port is H or L after the frequency fo is sent to a tuner. CONSTITUTION: A channel is selected via a key entry section 5 and data of a tuning frequency fo are given to a PLL IC of a tuner section 30. A video signal demodulated by a demodulation section 50 is detected by a video detection section 60 to discriminate the presence of a video synchronizing signal. An AFT(automatic fine tuning) port is checked. When the AFT port is at H, the tuning frequency is increased up to +2MHz by one slap (62.5kHz) each. When the level changes from H to L, it is discriminated that the point is a positive tuning point of the STD mode, the increment of the frequency is interrupted and a normal signal is received. On the other hand, when the AFT is at L, the frequency fo is decremented up to -0.5MHz by one step each, and when the level changes from L to H, it is discriminated that the point is a positive tuning point of the STD mode, the decrement of the frequency is interrupted and a normal signal is received.</p> |
