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.

 Description A very simple TV audio video transmitter circuit can be constructed using this schematic diagram . This TV audio video transmitter circuit can be used to transmit video signals from VCR ( or some other device ) to a TV without using any cable . Video signals input at jack J1 are first terminated by resistor R6 and coupled through capacitor C1 to clamping-diode D1. Potentiometer R3 is used to set the gain of the video signal; its effect is similar to that of the contrast control on a TV set. Bias-control R7 can be used to adjust the black level of the picture so that some level of signal is transmitted, even for a totally dark picture. RF-transformer T1 and its internal capacitor form the tank circuit of a Hartley oscillator that's tuned to 4.5 megahertz. Audio signals input at J2 are coupled to the base of Q3 via C2 and R4: the audio signal modulates the base signal of Q3 to form an audio subcarrier that‚s 4.5-megahertz higher than the video-carrier frequency. The FM ...

Description The power amplifier boosts 88-108MHZ 1-2W FM transmitter's power to 15 W. It includes multi-level low pass filter and has a high conversion efficiency with strong Yi-wave suppression. With good antena expected transmission coverage is at least 15Km. It uses high power 175 MHZ 4A 25W 2SC1972 RF transistor that must to be mounted to heatsink for proper heat dissipation. To maintain 88 ~ 108 MHZ with any frequency output reached rating, according to the level before the center frequency of some components to make suitable adjustments. May, when necessary, to reduce low-ball-series, to increase power output. The expansion of the power signals from three low-pass filter Yi-filtered high element of the transmitting antenna feed. Components choice: In addition to electrolytic capacitor, the other tiles with high-frequency capacitors, C11, C12, C14 use high-frequency characteristics of a good, stable performance of adjustable capacitors, inductors Choke RFC1, RFC2 finished with...

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.

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...

AM Transmitter circuit  To this powerful AM transmitters are huge, using ceramic tuning 3.587 mhz resonator and resonator filters are also sold with a value of 5.5 mhz, 7.7 mhz and 10.7 mhz. Distance transmitter range is approximately 2-4 km. the working principle of this circuit are filter resonator/ceramic filters raise the frequency of the value of the resonator filter. This frequency is amplified by the transistor can be changed t1. Frequency so need C7 as a regulator / placement. sound signal superimposed over the audio transformer.frekuensi which awakened by resonator filters and t1 is fed to the next amplify strengthened so as to achieve the desired power passed to antenna. t2 and t3 as a buffer as a final power amp. AM Transmitter Schematics AM radio / receiver circuit For AM radio because it's hard to find IC ZN 414 then now could be replaced with the equivalent of IC MK 484. Frequency coverage between 550 kHz-1600 mhz...

This circuit is a video transmitter that has many uses, such as video cameras, security cameras, satellite receivers, DVD, Video Games, etc. .. The circuit transmits 470-580MHz and can be tuned in the UHF channels 21-34. The video transmitter can reach up to 300 meters in open field using a wire antenna of 10-20 cm. TV Video Transmitter Circuit Diagram Video Transmitter Transmitter can work with a voltage from 9 to 15 volts. However, you can also use a 9v battery. Oscillator is based around BF199 and BFR90 is the RF transistors. If necessary, the transmission power can be increased by replacing with BFR90 transistor 2N3886.

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...

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...