BA1404 and upc1651 produced by the modulator circuit

BA1404 is Toyo's products, operating voltage range of 1 ~ 3V, the circuit is from the FM stereo mixer, 38KHZ oscillator, FM modulator and high-frequency amplifier monolithic integrated circuit.

Works (see Figure I): stereo audio signal and by increasing the input matching network consists of 1,2 feet, the amplified FM stereo into the mixer, to produce a main signal from the L + R and LR stereo sub-signal composite signal composed of amplified by the buffer from 14 feet out (16,17 feet to adjust the parameters of the composite signal, can control the left and right balance); 4,5,6 pin external discrete components and internal oscillator circuit 38KHZ 38KHZ signal by the buffer supply of mixers and amplification, respectively, 1 / 2 divider, 38KHZ 19KHZ signal by the divider to get a pilot signal from 13 feet out; 13-14 feet out from the composite signal and the pilot signal by the matching network consists of 11 feet into the FM Modulator (9,10 feet of production sub-component to determine the external oscillation frequency) to produce a FM signal, the amplified output from 7 feet; 2 feet for the AF offset 3 feet for the AF ground point, 8 feet is the RF connection location, 15 feet for the positive power supply. (Note: a reference voltage output pin 11 to facilitate external discrete components to control the oscillation frequency, where not used.) 7 foot by μpc1651 final amplified output signal.

Production Highlights: circuit board can be used in the million-intensive to install, to remove the excess copper point; 13,14 feet, only the reference value of resistance, because of its value on the stereo separation are related, according to the actual situation given value; L for the iron shell variable inductance, its parameters and frequency-related, here is the critical frequency stabilization, be careful; If you want electricity supply, pay attention to power, the current small, discrete filter can be regulated power; μpc1651 the working voltage is 5V, not exceed, easy to burn.

Experiment Summary: As the "electronic newspaper" BBS there are many users requiring detailed information on the FM stereo transmitter, so I re-collect the relevant information on the simple discrete, merge, integrated FM stereo transmitter experiment, that The BA1404 + μpc1651 mix of the most easy to make and debug, and very high frequency stability (relative to the previous circuit BA1404), transmission power does not exceed the statutory range.

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