| 摘要 |
PURPOSE:To obtain a normal trigger signal even when the channel separation is 1/2 of a predetermined value by shifting the center frequency of the IF selective circuit of the trigger circuit 12.5kHz in either direction from IF frequency. CONSTITUTION:Output of IF amplifier 11 (for example, 10.7MHz) is added to the trigger amplifier 12, while the base signal source output (11.52MHz) is added to the amplifier 12, subjected to mixing by means of the mixer 121 and converted into the signal of 820kHz. The synchrobnizing frequency with the above is amplified by the 12.5kHz shifted amplifying portion 12, detected by the wave detector 14 to obtain the trigger output. Thus, the receiver frequency of PLL synthesizer is retained at 50kHz spacing and can automatically select the frequency of odd number times of 25kHz. |
