Product Review

Description:
1. Frequency Modulation (FM) section
CD9088 is a dedicated single-chip FM radio chip,
Its simple external circuit, the circuit was built frequently 70KHZ phase locked loop system, selectively implemented by active RC filter, mute circuit can be suppressed non-IF signal and the IF signal is too weak.
FM signal input circuit rod antenna C8 / C10 and L1 IC1 11, 12 feet into the mixer circuit, local oscillation circuit uses a variable capacitor CA / L2, etc. vitality can be achieved manually tune.
Circuit R2 / C2 to squelch circuit, 3 feet to the audio loop filter capacitor C4. Indirect C13 6,8 feet of the intermediate frequency feedback capacitor, 7 feet is connected to C14 was the low-pass capacitors,
between C17 of 8/9 feet is IF coupling capacitor , 10 feet connected to the C12 is a limiting amplifier low-pass capacitors, 13 feet connected to the C6 of the limiter offset voltage capacitors.
2. Amplitude modulation (AM) section
AM band using Direct IC TA7642, TA7642 IC has 10 transistors internal composition, its appearance uses encapsulation mode a TO-92,1 feet grounded, 2 feet input , 3 feet output. Audio signal output from 3 feet, through R6 / C18 is coupled to the input of the power amplifier IC TDA2822 the power amplifier, pushing the speaker working.