![]() We can power this circuit by using a 9V battery or small voltage and package battery. The length of the antenna should be long so that the transmission will be efficient and receiver would be able to pick noise free signal.Transmitter circuits are very fun to work on, try it out and post your opinions about this circuit. We make a simple and small FM bug transmitter circuit designed by using a single transistor and a few oscillating elements, which can be constructed in small size PCB or general-purpose PCB. It consists of a simple oscillator with silicon planar RF PNP transistor. The Tank circuit with C5,C6 and L1 together with the Transistor Q2 forms the Oscillator part in the circuit.The resistors around the Transistor Q2 set the working point for Q2 and to limit modulation in FM band which is 80-130 MHz. This simple transmitter allows you to broadcast on FM radio band 87.5 - 108 MHz. If you are looking for an FM radio circuit which should be as small as possible yet have a very high accuracy in terms of band selection, then you can try the following concept. What is FM Transmitter An FM (Frequency Modulation) transmitter circuit is an electronic device that uses radio frequencies to transmit signals wirelessly. This bug has an effective range of about 100 meters. However, it will be difficult to obtain the oscillation at 100 MHz. To harness and prove this, I made the transistor oscillate in the FM band, then injected an AF voltage on the collector to vary the C-B junction capacitance. Allowing you to tun it to an open frequency on an FM Radio and listen to what is going on in the room you leave that bug in. FM transmitter FM carrier frequency can be calculated by the LC tank (L1 and 33pF) 1 1 21VLC 27L1 33pF We would like to design an FM transmitter that radiates around 100 MHz. The Q1 acts as the amplifier, it amplifies the audio signal from the microphone.R2-R4 are there in the circuit in order to set the working point of the transistor.C1 and C2 in the circuit acts as blocking capacitors so only AC signal can go through them. Simple FM transmitter using a single transistor: Transmitters: Mar 23, 2015: 1: Simple quiz display using 74 series logic chips: Games: Mar 23, 2015: 2: Single chip dice using a 4060 chip: Games: Dec 07, 2014: 1: Solid-state voltage indicator with high voltage cutout: Power: Dec 07, 2014: 0: Sound operated music bell using 555 timer: Alarms. The FM Listening Bug Kit gives you all you need to build a small, single Transistor, FM transmitter that can operate between 80 MHz and 150 MHz. The above circuit was very simple and uses only 9V and a mike for feeding audio input to the transmitter circuit.The circuit can be divided into three parts for simple understanding that is oscillator,Modulator and amplifier. How does the transistor act as a varicap to perform FM. FM circuit holds a significant position in wireless communication.This circuit uses a single transistor transmit noise free FM signal to the distance of about 50-300 meters.The transmitted signal from the transmitter can be received by means a simple receiver circuit which have the facilities of FM. ![]()
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