Simple MP3 FM Transmitter

---

A simple MP3 FM transmitter circuit shown here can be built easily in few minutes if all parts are available to you. All the components used in this transmitter circuit are general purpose and low cost. The circuit will work as a best FM transmitter for simply broadcasting your music around your house and yard, and can be used to broadcast the output of any equipment like mp3 player, ipod, satellite, etc. 

Simple FM Transmitter with BC549

---

This is simple FM transmitter for FM broadcast band in 88-108 MHz. BC 549 is small signal transistor for wide applications, but usually for AF. You can build simple FM transmitter with one BC549 transistor and several other component parts. Simple FM transmitter with only one transistor is often called “bug”. This project is suitable for beginners in radio amateur, education, or hobbies. As an antenna you can connect 150cm of copper wire. 

100m Simple FM Transmitter

---

Here is a very interesting and simple FM transmitter used to transmit audio in the wide range up to 100M using only one transistor. The entire circuit of FM transmitter is divided into three major stages oscillator, modulator and amplifier. The transmitting frequency of 88-108 MHz is generated by adjusting VC1. The input audio generated by microphone is changed into electric signal and is given to base of transistor T1. Transistor T1 is used as oscillator which oscillates the frequency of 88-108 MHz. The oscillated frequency depends upon the value R2, C2, L2 and L3. Transmitted audio from FM transmitter circuit can be received by standard FM receiver. 

Sun Tracking Solar Panel

As the non renewable energy resources are decreasing, use of renewable resources for producing electricity is increasing. Solar panels are becoming more popular day by day. We have already read a post about how to install solar panel for home. Solar panel absorbs the energy from the Sun and is stored in the battery. This energy can be utilized when required. Utilization of the energy stored in batteries is mentioned in below given applications. Solar panels should absorb energy to a maximum extent. This can be done only if the panels are continuously placed towards Sun direction. So solar panel should continuously rotate in the direction of Sun. This article describes about circuit that rotates solar panel.

Street Lights that Glow on Detecting Vehicle Movement

Generally, street lights are switched on for whole night and during the day, they are switched off. But during the night time, street lights are not necessary if there is no traffic. Saving of this energy is very important factor these days as energy resources are getting reduced day by day. Alternatives for natural resources are very less and our next generations may face lot of problems because of lack of these natural resources. We have already seen the circuit diagram and working of Auto Intensity Control of Street Lights circuit in the earlier post. This article describes about the circuit that switches the street lights on detecting vehicle movement and remains off after fixed time.

Logic Gates

Logic Gates 

 

 

Logic gates are the basic building blocks of digital electronics. These are circuits made out of transistors that perform a a logical operation (see Boolean algebra).

Digital electronics represent data (called bits) with only two states. Since in electronics we work with voltages, these two states are most times represented by a presence or lack of voltage. One (high state) in TTL logic familiy is represented by 5v, zero (low state) is represented by 0v (ground).

There are three basic gates: AND, OR, and NOT (Inverter).
Other common gates are NAND, NOR, XOR, XNOR (Equivalence). These gates are made with combinations of the basic logic gates. Its functions can be represented using a truth table, which lists every combination of inputs (A, B) and the resulting output (Z).

 

 

1W PLL Transmitter with MC145152

 

 

Following 1W PLL transmitter exciter provides stable, low noise operation. Transmitter uses a PLL frequency synthesizer built with MC145152 which covers the FM band in 100kHz steps. The VCO uses MV2109 varicap diode to automatically tune to selected frequency via SW1 dip switch. output stage uses 2N4417 RF power transistor and provides 1W of RF power. With good antenna expected transmission range is 2km. Transmitter may be built on a double sided PCB, with top side copper left mostly undisturbed as a ground plane. The copper is removed only around non-grounded pins. The ground connections can be soldered on the top side, so it’s not necessary to have plated-through holes. 

Veronica 1W FM Transmitter

Veronica 1W FM Transmitter

Veronica 1W FM transmitter is an easy to build transmitter. Veronica is also known for frequency stability, clean FM signal and uses no integrated circuit. The Veronica oscillator is actually formed from 2 oscillators which operates somewhere around 50 MHz in anti phase and the 2 signals are combined to form 100MHz FM radio signal. This kind of circuit design is stable and is amplified up to 1W by 2n4427 transistor. Veronica transmitter is equipped with a mini-mixer and so you may forget an external mixer. This consist from T1 transistor which amplifies the microphone signal before it is combined with CD player audio or PC signal. R1 and R2 are potentiometers (variable resistors) used to adjust the audio level. The component between R8 and C21 represents the oscillator which generates radio signal. D1 is a varicap diode (like a variable capacitor or trimmer) controlled by audio signal. C12, C13 and L1 determines the frequency.

18W FM Transmitter

 

 

 

Here's FM transmitter for commercial FM band that provides 18 watts of power. Since the electronic diagram is too large we decided to divide it into two parts. The first part is the actual FM transmitter while the second part is 18W RF amplifier. The circuit should be built on an epoxy printed circuit board with the upper face components reserved for interconnecting tracks and the bottom solder to the ground plane. If powered by 14V and 2.5A transmitter outputs 15W of power, whereas 18V and 3.5A will provide 18W. BB110 variable capacitor connected to the collector of transistor BF199 adjusts the transmission frequency of the circuit. 2K2 potentiometer serves as fine tuning. Once the output frequency is adjusted amplifier variable capacitors must be adjusted for maximum output power one stage at a time. All adjustments must be made with 50 Ohm dummy load connected to the output of transmitter.  

 

1 Watt FM Transmitter Amplifier

 

 

This is a 1 Watt FM Transmitter amplifier with a good design that can be used to amplify a RF signal in the 88 – 108 MHz band. It is very sensitive if you use good RF power amplifier transistors, trimmers and coils. It has a power amplification factor of 9 to 12 dB (9 to 15 times). At an input power of 0.1W the output will be 1W. You must choose T1 transistor depending on applied voltage. If you have a 12V power supply then use transistors like: 2N4427, KT920A, KT934A, KT904, BLX65, 2SC1970, BLY87. At 18 to 24V power supply you must use transistors like: 2N3866, 2N3553, KT922A, BLY91, BLX92A. You may use 2N2219 at 12V but you will get an output power of 0.4W maximum.

Calibration of the 1 watt fm power amp
Do not connect any RF source, just apply the power supply and measure the voltage at point 1. Adjust R3 until you measure 0.7V. Replace the antenna with 2 x 100 Ω 0.5W resistors in parallel at the RF output. Now connect the rf signal that you need to amplify and connect this RF Probe to the output.
Slowly adjust C1 in order to get the highest voltage value on the rf probe. Now adjust R3 again to get 0.7 V at point 1. Now adjust C5 and C6 for maximum output voltage (must be between 12V to 18V).

Check the temperature of T1′s heatsink, if it is ok turn off the power supply, disconnect the 2 resistors of 100 Ω and connect the antenna (keep the probe connected). Apply the power and now adjust again C1, C5 and C6 for maximum voltage indication on the probe.

You may use an ampermeter in order to check the current flow through T1. This must not exceed 150mA at 12V and 100mA at 24V or the transistor will burn. L2 and L3 coils must have an angle of 90 degrees between them. Don’t use the 1W rf fm amplifier if you find that you tv set is jammed and the laws of your country does not allow the use of FM transmitters.

4km FM Transmitter

 4km FM Transmitter

This is a VCO FM Transmitter. With good antenna (dipole placed outdoor and high) the transmitter has very good coverage range about 500 meters, the maximal coverage range is up to 4 km. To calibrate for maximum power connect 6 V / 0,1 light bulb to the output and use R1 to tune the right frequency, adjust L1 coil if necesary. Then use C14 and C15 to adjust the highest power (the highest light of the bulb). Then you can connect antenna and audio signal. Adjust R2 until the audio sounds as loud as the other stations. 

27MHz Walkie Talkie

27MHz Walkie Talkie

 

This classic walkie talkie consists of both 27MHz transmitter and receiver all in one circuit. Nearly all the components in the 4-transistor circuit are used for both transmitting and receiving making it simple to build and economical at the same time. The frequency-generating stage only needs 27MHz crystal to be removed and it becomes a receiver. Next is a three transistor audio amplifier with very high gain. The first transistor is a pre-amplifier and the next two are wired as a super-alpha pair, commonly called a Darlington pair to drive the speaker that is also used as a microphone. The use of telescopic antenna will provide better reception and transmitting range. Use two identical walkie talkie circuits for two way communication. 

Phone Transmitter

 

 

This small phone transmitter will transmit a phone conversation to an FM radio on the 88-108MHz band. It uses energy from the phone line to transmit the signal about 100 meters away. It uses the phone wire as the antenna and is activated when the phone is picked up. Transmitter components are mounted on a small PC board. PC layout is included.

 

 

Mini FM Transmitter

 

 

Here's how to build your own mini FM transmitter. It transmits FM waves so you could easily receive the signals on your mobile phone, radios, etc. As the name and the picture indicates it is very small and is approximately the size of a 9v battery clip. With this FM transmitter you could start your own mini FM station. The circuit uses BC547 transistor to amplify the signal and then frequency modulate it. It uses "frequency modulation" most commonly known as FM, the same principal to transmit audio signals captured by the microphone.

6W FM Transmitter 88-108 MHz

6W FM Transmitter 88-108 MHz

Presented FM transmitter is built around low power PLL transmitter and amplifier that boosts its signal all the way up to 6 Watts. The signal is amplified by three RF stages of amplification. In the first and second stages of the transmitter one of the best driver transistors were used 2SC2053. You can use the other transistors but only up to 500mW of power. In the third stage 2SC1971 RF transistor was used to achieve 6W of power. For making any RF transmitter circuit at least two meters are necessary, one is frequency counter and the other is RF field strength meter for which the schematic is provided. 

Easy FM Transmitter

 

The figure shows a schematic of an easy to build FM transmitter circuit. Mostly all FM transmitter circuits you will find online or in books require some kind of hand build inductor/coil and after building the transmitter you have to adjust that coil and trimmer capacitor a little to adjust the transmitter to transmit on your desired frequency. If you are looking for an easy or simple FM transmitter circuit in which you don't have to make a coil with your hand then the circuit given here is ideal for you. The circuit is using a ready made 1uH inductor which can be purchased from an electronic components store. These inductors are mostly look like resistors. The circuit also does not require a trimmer capacitor, because we have used a fixed value of 39pF capacitor in the place of trimmer capacitor. We have already calculated and used the values of coil and capacitors of oscillator to broadcast on FM band, so you don't have to do any further adjustments and tuning after building the circuit. The circuit can be operated with 9 to 12 volt DC. For antenna use a 12 inch wire or for maximum range use a 30 inch wire and make it vertical.

Note: If the circuit is not broadcasting on your desired frequency then you can change the value of 39pF capacitor a little bit higher or lower to change the frequency.