Self-made 45-870MHz FM receiver

The machine uses the drawing good TDQ-38-type addition of high-frequency head and the whole composition of the finished products by the LA7533 release box, which receives high sensitivity, stable performance, and making easy. The machine can receive 45-870MHz FM signal to all within, and can be used to listen to FM radio, TV audio and radio and cordless phone signals; with audio and video signal output port, can monitor the whole package to become a TV channel receiver can be used as audio and video repair television signal source when.
    Circuit, see picture on the right. LNB output of 38MHz and 31.5MHz all TV audio signal directly into the first IF signal box to put the finished intermediate frequency amplifying and detector and frequency discriminator, the output of audio and video signals were treated with C5, C6 coupled to the audio and video output. W2 audio volume potentiometer also been adjusted into the IC2 (ULN2283B) audio amplifier circuit formed by the amplified output to the speakers, the output power 1W.
    IC1 (CD4017) composed of L, H, U tri-band touch electronic conversion circuit, and the two-color LED LED1 respectively red, green, and yellow directions. L band frequency is 45MHz ~ 150MHz, H band frequency is 142MHz ~ 380MHz, U-band frequency is 375MHz ~ 870MHz.
     Tuner sensitivity should be used all added to the type of high quality product, the complete elimination of common radio sensitivity is low, and poor string of Taiwan and selective. LA7533 put boxes in the use of finished products, audio frequency is 6.5MHz, the built-in a pre-amplifier and SAW filter and LA7533 in the release block; single row of 11 pin arrangement, which for the IF input pin ①, ② feet grounded ③ pin 12V power supply connected, ⑥ pin for audio output, ⑦ pin 6.8V AGC voltage output side, ⑩ pin video output, shell be grounded.
    IC2 audio amplifier block model ULN2283B, if it can not easily buy into the composition of the LM386 audio amplifier circuit. Tuning potentiometer W1 choose 220KΩ TV field frequency adjustment potentiometer, tuner direct DC 30V mini header.

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