This Audio Video RF modulator application working on VHF UHF Band uses a MC44BS374TI from Freescale. MC44BS374 is audio and video modulator for use in Transmit Video audio and similar device.
These IC are the next generation of the MC44BC374TI with the following new features :
- TV output level 83dBuV
- 5V and 3.3V compatible I2C bus
- Logic Output Port pin (pin 3) available
SCHEMATIC DESCRIPTION
Download Schematic in PDF format, Trial HEX CODE
A MC44BS374 audio video RF modulator IC is used to provide the RF output and amplified by RF IC UPC2709 and UPC1678GV. It will have output about 17mW. The TV modulator is controled via microcontroler I2C interface and can tune the R.F Output to broacast channel. Microcontroler will set the frequency to 471.25Mhz - 895.750Mhz and have frequency step 250Khz. The modulator can set to VHF, it only depending on which software is used.
The audio video RF modulator IC has two input. One called Audio Input, and one called Video input. You can directly attack your VCD/DVD output to this modulator and transmit to UHF frequency.
To change frequency use either up or down buttons, it will change frequency with 250Khz. Status button will have some function: Read Memory, Write Memory, Reset Memory and Lock status of the modulator.
The microcontroler is used to control I2C and drive LCD 2x16 Display. it will set the frequency, PWC (Peak white clip) default is on (System B/G), Sound Carier default is set to 5.5Mhz (PAL System), Picture to sound ratio 12dB, etc. Source: Audio Video RF Modulator
See more: FM Preamplifier - TV Transmitter - Transistor FM Transmitter
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