Wireless Transmitter


Posted on Feb 7, 2014

A basic circuit of the transistor UHF radio transmitter with surface acoustic wave resonator (SAW), and the SAW is used as a positive feedback element connected between the transistor VT base and LC network in parallel. Figure (b) shows another basic transistor UHF radio transmitter circuit with the surface acoustic wave resonator


Wireless Transmitter
Click here to download the full size of the above Circuit.

, in this circuit, SAW is connected between the transistor`s base and emitter; the phase relationship between them is 180 degree. (View) This transmitter is basic but allows transmission of audio to an AM radio. It consists of an RF oscillator operating in the AM broadcast band, together with a modulator stage, which mixes the incoming audio and the RF. A signal appears on the output, which has an AM component that can be picked up on a nearby AM radio receiver. The transmitter consists of oscillator stage Q1 and modulator/buffer stage Q2. Q1 is biased via R1, R2, and R3. L1, C3, and C4 form the tank circuit with feedback network C3-C4 providing feedback to the emitter of Q1. RF voltage at the junction of C3 and L1 drives buffer/modulator stage Q2. Q2 is biased by base current produced by RF rectification in the base emitter junction of Q2. C6 is an RF and AF bypass capacitor. C9, C10, and L2 form the tank circuit for the collector of Q2. RF is taken from the junction of C9 and C10 and fed to a short-wire antenna. Audio is fed to modulator Q2 via C8 and isolation resistor R5 and mixes with the RF signal in the collector circuit of Q2, producing a signal that has sum and difference frequencies if the RF carrier and AF input along with the carrier signal. An AM signal appears at the collector of Q2. Audio with an RMS voltage equal to about 0. 7 times the collector voltage of Q2 is needed for full modulation of the output....




Leave Comment

characters left:

Related Circuits

  • New Circuits

    .

     


    Popular Circuits

    OSCCAL Value Finder Board with 16F88
    PIC16F627A Touchpad circuit
    Automatic blind hooked up to existing projector screen using Arduino
    FM Wireless Microphone Transmitter with High Power
    door loock circuit
    555 timer circuit temperature monitoring system
    Definition of a Hartley oscillator
    Simple Pyro RF Receiver (27 MHz) - Signal Mixing
    AM radio rf amplifier
    As one of the thyristor type delay circuit
    Closed loop speed control



    Top