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For those of you like / love to talk in the air can assemble this simple circuit that can be received by the radio receiver to within a few hundred feet. The voice that issues by this circuit at all clear without rustling. Can also be used to link communications over the air using this radio transmitter, provided that other person also had the same circuit. This PCB design : Description : Resistor R1__________________1K R2__________________18K R3__________________82K R4__________________1K2 R5__________________5K6 R6__________________39K R7__________________18K R8__________________68K R9__________________470R R10_________________100R R11_________________50K XTal Q1__________________ Crystal according to the desired frequency Inductor L1__________________10uH Capacitor C1__________________10uF C2__________________30uF C3__________________20uF C4__________________47uF Transistor Tr1_________________2SB175 Tr2_________________2SB175 Tr3_________________2SB178 Antenna X1-1________________...

Description The use of transmitters which have a more powerful output than the ‘ flea-power ’ are sometimes required when there are many obstacles in the path of the surveillance transmitter and monitoring station receiver, or the distance between them is too far so as to make a low powered device feasible. Whereas a typical micro transmitter will produce an RF power in the order of just a few milliwatts, i.e. a few thousandths of a watt, the VHF-FM transmitter described has a power output of between around a half and 2 watts, depending on the power source, which may be anywhere between 6 volts and 30 volts d.c. The battery or batteries should be of the alkaline high power type, since the current drain will be found to be relatively higher when compared to microtransmitter current drain. The power output of this device is somewhat proportional to the current drain and so therefore both may be decreased by altering the val...

This circuit is a circuit diagram is included in the RF circuit. FM Transmitter circuit diagram using the IC BH1417. Where the integrated circuit design from RHOM which includes many features in one small package. He came with pre-emphasis, limiter so that music can be transmitted in the same audio level, stereo encoder for stereo transmission, visit page. FM Stereo Transmitter circuit diagram

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...

   4 Transistor FM Transmitter Circuit Diagram Build a  4 Transistor FM Transmitter Circuit Diagram. This 4 Transistor FM Transmitter Circuit Diagram provides an FM modulated signal with an output power of around 500mW. The input microphone pre-amp is built around a couple of 2N3904 transistors (Q1/Q2), and audio gain is limited by the 5k preset trim potentiometer.  The oscillator is a colpitt stage, frequency of oscillation governed by the tank circuit made from two 5pF ceramic capacitors and the L2 inductor. The output stage operates as a 'Class D' amplifier, no direct bias is applied but the RF signal developed across the 3.9uH inductor is sufficient to drive this stage. The emitter resistor and 1k base resistor prevent instability and thermal runaway in this stage.

This electronic circuit is a simple VHF FM transmitter circuit. The circuit can easily make portable use for a small 9 volt battery. Transmitter range from 60 to 100 meters range.  The construction of the circuit is very simple. Electrically adjustable frequency between 88 and 108MHz. Portable and low power consumption. You can use any FM receiver. 9 Volt works. Portable and Low Power VHF FM Transmitter Circuit Diagram Parts list: R1 = 10K R2 = 15K R3 = 3.3K R4 = 470 ohm R5 = 100K R6 = 4.7K VR 1 = 10K Pot meters VALUE C1 = 0.1uF----- 104 C2 = 0.001uF---- 102 C3 = 0.0015uF---- 152 C4 = 10pF ----- 10 C5 = 3pfF ----- 3 C6 = 2.5pF----- 2.5 C7 = 10pF ----- 10 C8 = 0.01uF---- 103 C9 = 0.022uF----- 223 C10 = 1pF ----- 1 C11 = 0.001uF---- 102

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.  Four-Stage FM Transmitter Circuits diagram : Four-Stage FM Transmitter Circuits Diagram 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 di...

You'll find that this is a very easy project to build. It will transmit good quality sound in the FM band ( 88 - 108 mhz ). One inportant item is that the IC chip operates on 3 volts DC. The chip will get destroyed if it is operated on any voltage higher than 3.5 volts. The antenna can be a standard telescopic antenna or a 2 foot length of wire. The input is in the millivolt range and you may need to add additional pots for the inputs. I was able to use this circuit for a walkman and a portable CD player in my car. I used the headphone jack on both and varied the signal with the volume control. FM Stereo Transmitter Circuit Diagram To adjust the circuit tune your FM radio to a quite spot then adjust the trimmer capacitor C8 until you hear the signal that you are transmiting. When you have a strong signal adjust the resistor R4 until the stereo signal indicator lights. If the input is to high of a signal you may over drive the IC chip. Use two 15 turn pots on the input signals to b...

The use of transmitters which have a more powerful output than the ‘flea-power’ are sometimes required when there are many obstacles in the path of the surveillance transmitter and monitoring station receiver, or the distance between them is too far so as to make a low powered device feasible. Whereas a typical micro transmitter will produce an RF power in the order of just a few milliwatts, i.e. a few thousandths of a watt, the VHF-FM transmitter described has a power output of between around a half and 2 watts, depending on the power source, which may be anywhere between 6 volts and 30 volts d.c. . Circuit diagram : Long Range FM Transmitter Circuit diagram The battery or batteries should be of the alkaline high power type, since the current drain will be found to be relatively higher when compared to microtransmitter current drain The power output of this device is somewhat proportional to the current drain and so therefore both may be decreased by altering the value of R6 to a...

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...

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. 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 a PCB, you can...

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...

This portable AM and FM radio circuit is designed using the LA1800 IC and some other external components. As you can see in this circuit diagram the LA1800 manufactured by Sanyo Semiconductors , require few additional components. The LA1800 am FM portable radio circuit needs to be powered from a 3 volt DC power supply circuit. AM and FM Radio with LA1800 Portable Project You can use an 3 volt battery. This radio receiver circuit has a low current dissipation of 5.6mA for FM band and 3.2mA for AM band .Also the output signal is driven into earphone speakers , but you can use an additional speaker ( in that case you need to connect an additional small power audio amplifier).

This the fm wireless transmitter circuit, the truth is one kind microphone that developed to be used without a cable from the microphone to the amplifier. Makes flexible to use than a plain microphone much Because without cumbersome cables. And also save a microphone cable as much Because microphone cable is high quality that has relatively high prices. How it work When we speak, the microphone will receive the audio signal is mixed with range FM frequency to transmit the broadcast spectrum. The audio input is just bring to the FM radio receiver tuned provide the radio only. The detailed procedures are as follows. In Figure this circuit has very little equipment, MIC is used in the circuit be special that called the condenser microphone, inside the MIC has an one amplifier section Serves to amplify the voice that speaks to the strength increases and send to the output. So this MIC must a current one to them. Please note the circuit is supplied to the resistor 27K positive in the leg mi...

Build a Simple FM Transmitter Circuit Diagram . This FM transmitter is about the simplest and most basic FM transmitter it is possible to build and have a useful transmitting range. It is surprisingly powerful despite its small component count and 3V operating voltage. It will easily penetrate over three floors of an apartment building and go over 300 meters in the open air. The circuit we use is based on a proven Australian design. It may be tuned anywhere in the FM band. Or it may be tuned outside the commercial M band for greater privacy. (Of course this means you must modify your FM radio to be able to receive the transmission or have a broad-band FM receiver.)  The output power of this FM Tx is below the legal limits of many countries (eg, USA and Australia). However, some countries may ban ALL wireless transmissions without a license. It is the responsibility of the builder to check the legal requirements for the operation of this circuit and to obey them.   Simple...

Block diagram of FM transmitter and receiver and its explanation FM transmitter Frequency Modulation is the process in which the frequency of the carrier signal is varied by the modulating signal while the amplitude remains constant Using Reactance modulator direct method The FM transmitter has three basic sections. The exciter section contains the carrier oscillator, reactance modulator and the buffer amplifier. The frequency multiplier section, which features several frequency multipliers. The power output section, which includes a low- level power amplifier, the final power amplifier, and the impedance matching network to properly load the power section with the antenna impedance. The essential function of each circuit in the FM transmitter may be described as follows. The Exciter The function of the carrier oscillator is to generate a stable sine wave signal at the rest frequency, when no modulation is applied. It must be able to linearly change frequency when fully modulated, w...