Do More

This is a Small Circuit Multiband Radio -Transmitter CW for who wants to learn more about radiofrequency, mainly operating principle from radios transceivers multiband, That circuit consists of a frequency oscillator RF, which is the main component us transmitters and radio receivers.  He oscillates for high frequency, he is called variable frequency oscillator or VFO, their frequency may vary of 5.2 MHz to 15 MHz, depending the coil chosen and signal can be received in the band shortwave by any receiver radio.In S1 is used a switch type bell, but can-if use a handler CW, these used by radio amateurs. How antenna should-if use a the type dipole from 1/4 wave.

This FM transmitter circuit is very simple and it has a acceptable transmission . The signal transited from this FM transmitter circuit can be received at almost 300 meters in open air .The circuit require a 3volts operating voltage and can be tuned anywhere in the FM band.The coil should be about 3mm in diameter and 5 turns. The wire is tinned copper wire, 0.61 mm in diameter.After the coil in soldered into place spread the coils apart about 0.5 to 1mm so that they are not touching. If you don’t have a trim cap you can use a fixed value capacitor and you can vary the TX frequency by adjusting the spacing of the coils or placing a small piece of ferrite inside the coil , but the better way to change the transmission frequency is to use a variable capacitor .Connect a half or quarter wavelength antenna (length of wire) to the aerial point. At an FM frequency of 100 MHz these lengths are 150 cm and 75 cm respectively.

The power output of many transmitter circuits are very low because no power amplifier stages are incorporated. The transmitter circuit described here has an extra RF power amplifier stage, after the oscillator stage, to raise the power output to 200-250 milliwatts. With a good matching 50-ohm ground plane antenna or multi-element Yagi antenna, this transmitter can provide reasonably good signal strength up to a distance of about 2 kilometres. Simple Long Range FM Transmitter Circuit Diagram : The circuit built around transistor T1 (BF494) is a basic low-power variable-frequency VHF oscillator. A varicap diode circuit is included to change the frequency of the transmitter and to provide frequency modulation by audio signals. The output of the oscillator is about 50 milliwatts. Transistor T2 (2N3866) forms a VHF-class A power amplifier. It boosts the oscillator signal power four to five times. Thus, 200-250 milliwatts of power is generated at the collector of transistor T2. For bett...

LM567 Infrared Transmitter Circuit This infrared transmitter use PWM (pulse width modulation). The transmitter is equiped with LM567, tone decoder circuit. Audio signal ( at least 50mVvv ) is amplified with T1 and then it is used to modulate IC1. Infrared transmitter frequency is adjusted with P2 between 25 and 40KHz. LM567 Infrared Transmitter Circuit

Description 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. Circuit Schematic Diagram 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 f...

  This term was coined by Honeywell, USA in 1985. The first generation of instruments like flow meters were mechanical devices. The next generation used electronics for improving performance. With electronics, adjustment of range, span, zero adjustment etc. could be carried out with potentiometers. (i.e. ease of setting parameters was achieved) In some cases functions like linearization, annunciation (exceeding process limits) etc. were also integrated. With the help of 4-20mA transmitter, data transmission over longer distance was made easy. There was a considerable jump in technology in terms of improved accuracy, response, interface with operator, ease of adjustment of range and span. This was made possible with use of digital circuits, microcontrollers, ADC, DAC. Today we hear about not only Smart Transmitter/Instruments, but Smart Control Valves, Smart Machines like Microwave Ovens, Washing Machines etc. Digital Oscilloscope also can be categorized as Smart Oscilloscope. Most...

This device connects to your audio input and output video from a cassette player or a camcorder and thus pass through the air to one or more televisions in the area of ​​a house. It is also useful to output the image and the sound of a computer to do multimedia presentations in several TV screens distributed in an enclosure. If you have a satellite TV service or premium cable system and want to watch programming on multiple televisions with a single tuner and / or decoder output can connect it to this project and enjoy the images in the house. Also useful in closed systems for security video, avoiding large number of cable runs. Domestic TV Transmitter Circuit Diagram As shown in the circuit diagram the circuit has several stages (a local oscillator, an FM modulator for audio an AM modulator for video, a mixer and an output amplifier) very simple to assemble. It has the controls necessary for achieving optimal fit and proper signal transmission. Circuit Description: The video signal en...

This low-power UHF FM transmitter is intended for remote control applications such as garage doors and wireless alarm systems . It is a single transistor design that operates at a frequency reserved for low-power wireless signalling. The operating frequency is determined by a resonator, F11. The following types may be used: UK: Type R2528 for 418 MHz; USA: Type Rl53O for 315 MHz; Holland, Belgium, Germany: Type R2554 for 433;92 MHZ: France: Type R2523 for 224.5 MHZ. The transmitter is frequency-modulated by an audio (or digital) signal applied to the junction of a varactors D1, D2 via R3. The varactors effectively change the shunt capacitance of the resonator as a function of the modulation signal, which results in FM. The design may be changed to produce AM (amplitude-modulation) by omitting components D1, D2, R2, R3 and R6, and interconnecting points ‘A’ and ‘B‘. Transistor T1 is fitted at the solder side of the printed circuit board, as indicated by the dashed outline on the compo...

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.   Lets start with getting all the parts. Components BC547 Transistor An microphone A variable capacitor 47pf An Inductor (see steps for description) 4.7k Resistor 330ohm resistor 1n capacitor (102) 10p capacitor 9V battery LED(optional) Tools Soldering Iron An FM receiver (any mobile phone) I got almost all of the components from a pile of old PCBs I had in an old forgotten box. All I had to get was the BC547 and the electret microphone. Actu...

This article should satisfy those who might want to build a low power FM transmitter. It is designed to use an input from another sound source (such as a guitar or microphone), and transmits on the commercial FM band - it is actually quite powerful, so make sure that you don't use it to transmit anything sensitive - it could easily be picked up from several hundred meters away. The FM band is 88 to 108MHz, and although it is getting fairly crowded nearly everywhere, you should still be able to find a blank spot on the dial. NOTE: A few people have had trouble with this circuit. The biggest problem is not knowing if it is even oscillating, since the frequency is outside the range of most simple oscilloscopes. See Project 74 for a simple RF probe that will (or should) tell you that you have a useful signal at the antenna. If so, then you know it oscillates, and just have to find out at what frequency. This may require the use of an RF frequency counter if you just cannot locate the ...

      This is the schematic for an FM transmitter with 3 to 3.5 W output power that can be used between 90 and 110 MHz. Although the stability isn't so bad, a PLL can be used on this circuit. This is a circuit that I've build a few years ago for a friend, who used it in combination with the BLY88 amplifier to obtain 20 W output power. From the notes that I made at the original schematic, it worked fine with a SWR of 1 : 1.05 (quite normal at my place with my antenna). Circuit diagram   Parts: R1,R4,R14,R15 10K 1/4W Resistor R2,R3 22K 1/4W Resistor R5,R13 3.9K 1/4W Resistor R6,R11 680 Ohm 1/4W Resistor R7 150 Ohm 1/4W Resistor R8,R12 100 Ohm 1/4W Resistor R9 68 Ohm 1/4W Resistor R10 6.8K 1/4W Resistor C1 4.7pF Ceramic Disc Capacitor C2,C3,C4,C5,C7,C11,C12 100nF Ceramic Disc Capacitor C6,C9,C10 10nF Ceramic Disc Capacitor C8,C14 60pF Trimmer Capacitor C13 82pF Ceramic Disc Capacitor C15 27pF Ceramic Disc Capacitor C16 22pF Ceramic Disc Capacitor C17 10uF 2...

Description: The following circuit shows about 88-108MHz FM Transmitter Circuit Diagram. Features: 1W transmitter Tetsuo style. Component:  Capacitor, Antenna, transistor, IC, diode.[thing.net]

Block diagram of AM transmitter and receiver with explanation AM Transmitter : Transmitters that transmit AM signals are known as AM transmitters. These transmitters are used in medium wave (MW) and short wave (SW) frequency bands for AM broadcast. The MW band has frequencies between 550 KHz and 1650 KHz, and the SW band has frequencies ranging from 3 MHz to 30 MHz. The two types of AM transmitters that are used based on their transmitting powers are: ·          High Level ·          Low Level High level transmitters use high level modulation, and low level transmitters use low level modulation. The choice between the two modulation schemes depends on the transmitting power of the AM transmitter. In broadcast transmitters, where the transmitting power may be of the order of kilowatts, high level modulation is employed. In low power transmitters, where only a few watts of transmitting power are required , low...