TREE

This circuit shows how to build a super-sensitive, mini-powered FM transmitter consisting of a RF (radio Frequency) oscillator section interfaced with a high sensitivity, wide pass-band audio amplifier and capacitance mike with a built-in FET (Field Effect Transistor) that modulates the base of the RF oscillator transistor. Transistor Q1 forms a relatively stable RF oscillator whose frequency and is determined by the value of coil L1 and turning capacitor C4. Part List : R1_______15K R2_______3K9 R3_______220R R4,R5____1K R6,R9____10K R7_______390K C1,C6____0.01uF C2_______4.7pF C3_______0.1uF C4_______6-35pf trimmer cap C5_______2.2uF B1_______3V L1_______Coil winding (see below) Q1,Q2____PN2222 M1_______Special FET bypassed microphone Assemble L1 : Form L1 by tightly wrapping eight turns of #16 bus wire on a #8 wood screw. Produces an eight-turn coil with an inner diameter of approximately 0.135 inches and lenght of about 0.625 inches. Insert in the proper hole and solder as shown.

This simple circuit FM radio receiver comprises a step of regenerating rf, TR1, followed by a two-stage three audio amplifiers, TR2 to TR4. A critical part of the FM radio receiver is the first stage, TR1/VC1 where the wiring should be kept as short as possible. Coil L1 consists of 8 turns of the winding 1 mm (20 AWG) enamelled copper wire 6 mm in diameter L1 should then be thoroughly and uniformly stretched to a length of about 13mm. Read more Small Circuit Multiband Radio  FM Radio Receiver Circuit Diagram The tuning capacitor VC1 is one of two sections of a fm radio FM miniature, it is connected to the capacitor C1 22pF. The inductance value L2 rf is not critical, since anything 1μH to 10μH. The output is suitable for common headphones connected in series to provide an impedance of 64Ω. List of Transistors TR1 = BF199 TR2 TR3 TR4 == = BC547

Circuit diagram: AM FM radio reciver circuit diagram Datasheet for TDA1083: Download

The project is a user-friendly and cheap FM radio receiver which produces the desired audio signals using integrated circuit to achieve the pre-processing units. During operation, the user is allowed to change stations and interact with the receiver by integrating a keypad and an LCD for communication. There are several functions that this radio receiver can perform including adjusting the threshold when picking up stronger or weaker stations, setting up 3 favorite stations for quick tuning, scanning up/down for next strong signal station, and tuning up/down a frequency. A keypad is designed for controlling the receiver and the buttons are mapped to their corresponding functionality while the other buttons are not connected. The 4 main sub-components of the receiver include the LCD, the keypad, the favorite station storage, and the communication with receiver. Each of them is being controlled by their software components. The antenna transfers the incoming radio signal to the AR1010 F...

A simple PLL FM demodulator circuit using IC XR2212 is shown here. XR2212 is a highly stable, monolithic PLL (phase locked loop) IC specifically designed for communication and control system applications. The IC has 0.01 Hz to 300KHz frequency range, 4.5 to 20V operating voltage range, 2mV to 3Vrms dynamic range, high temperature range, TTL / CMOS compatibility and adjustable tracking range. The block diagram of a typical PLL FM demodulator circuit is shown below. PLL FM demodulator block diagram The working of a PLL FM demodulator is very easy to understand.The input FM signal and the output of the VCO is applied to the phase detector circuit. The output of the phase detector is filtered using a low pass filter, the amplifier and then used for controlling the VCO. When there is no carrier modulation and the input FM signal is in the center of the pass band (i.e. carrier wave only) the VCO’s tune line voltage will be at the center position. When deviation in carrier frequency occurs ( ...

Warning: Take care with transmitter circuits. It is illegal in most countries to operate radio transmitters without a license. Although only low power this circuit may be tuned to operate over the range 87-108MHz with a range of 20 or 30 metres. Circuit diagram Notes : I have used a pair of BC548 transistors in this circuit. Although not strictly RF transistors, they still give good results. I have used an ECM Mic insert from Maplin Electronics, order code FS43W. It is a two terminal ECM, but ordinary dynamic mic inserts can also be used, simply omit the front 10k resistor. The coil L1 was again from Maplin, part no. UF68Y and consists of 7 turns on a quarter inch plastic former with a tuning slug. The tuning slug is adjusted to tune the transmitter. Actual range on my prototype tuned from 70MHz to around 120MHz. The aerial is a few inches of wire. Lengths of wire greater than 2 feet may damp oscillations and not allow the circuit to work. Although RF circuits are best constructed on...

This FM transmitter circuit uses four radio frequency stages: a VHF oscillator built around transistor BF494 (T1), a preamplifier built around transistor BF200 (T2), a driver built around transistor 2N2219 (T3) and a power amplifier built around transistor 2N3866 (T4). A condenser microphone is connected at the input of the oscillator. Working of the circuit is simple. When you speak near the microphone, frequency-modulated signals are obtained at the collector of oscillator transistor T1. The FM signals are amplified by the VHF preamplifier and the pre-driver stage. You can also use transistor 2N5109 in place of 2N2219. The preamplifier is a tuned class-A RF amplifier and the driver is a class-C amplifier. Signals are finally fed to the class-C RF power amplifier, which delivers RF power to a 50-ohm horizontal dipole or ground plane antenna. Use a heat-sink with transistor 2N3866 for heat dissipation. Carefully adjust trimmer VC1 connected across L1 to generate frequency within 88-108...

Designing various electronic circuit system (synthesizer, modem, decoder, data converter, etc) of ten need a frequency modulator subsystem. An FM modulator is very easy to build with TC9400 since the it has very good linearity as V/F converter. While Vin determines the amount of modulation (FM deviation) around the center frequency, the potentiometer determines the center frequency. Vin can be negative as well as positive. Superlinear FM Circuit Diagram

BH1417 IC The circuit shown here is of a good Stereo FM transmitter that can transmit high quality signals up to a range of 70 feet. The circuit is based on BH1417 PLL stereo transmitter IC from Rhom semiconductors. The IC has separate audio processing sections for the left and right channels, pre emphasis circuit for improving signal to noise ratio, crystal control circuitry for accurate frequency locking, multiplex circuit for making sum ( left plus right) and difference ( left minus right) {see this article for better understanding – Stereo decoder circuit} etc. Another important feature of this IC is that the transmission frequency can be set using a 4 channel DIP switch. The IC can be powered from anything between 4 to 6V DC and has an output power around 20mW. At full output power the circuit consumes only 20mA and has a channel separation of 40dB.There are 14 possible preset transmission frequencies, starting from 88.7MHz and incrementing in steps of 0.2MHz that can be selected ...

Let’s construct a low-power FM transmitter using surface-mount devices (SMD) that will be received with a standard FM radio. Soldering surface mounted devices is not so hard and actually is quite easy. There are many designs for small FM transmitters but they have some problems. First, you need an audio amplifier to get enough modulation. Second, the antenna is attached directly to the collector. Third, the coil L must be wound by hand and adjusted by stretching. It all ads with a weak signal that tends to drift in frequency. In contrastm the transmitter schematic we present here eliminates some of those problems, using varactor diode for tuning and modulation, givind great sensitivity without an audio amplifier. FM Transmitter – How it works The figure below shows the schematic of the transmitter which consists of two stages: an oscillator and an output amplifier. Modulation is from an electret microphone but you can use a low power audio source. Oscillator stage Transistor Q1 is a C...