FM 9V transmitter circuit with expllanation

This circuit diagram transmitter is a very simple and useful circuit that require few external components and operates in FM band ( above 100 MHz ) . This circuit diagram transmitter needs to be powered from a 9 volts battery or from another 9 volts regulated power supply . The tuned coil L1, has two output tappings for the antenna connection, marked "A" and "B". These are both low-level outputs and you choose which tapping you want to use ( stable low range, or more unstable but higher range). Tap B (2.5%) takes just a very small portion of signal from the oscillator circuit and therefore gives a very frequency stable transmitter. The output level (around 2.5mW) and range are therefore somewhat reduced. Tap A (10%) delivers very much more power (around 10mW) to the antenna load. This gives you a greater range, but at the expense of frequency stability. All component leads should be kept as short as possible. The LINK wire on the PCB should lay flat on the PCB. Use the cutoff from a resistor leg. Antenna length for circuit diagram transmitter varies with frequency for optimum distance: 90MHz 80 cm, 95MHz 75cm, 100MHz 70 cm, 105 MHz 68 cm. The frequency determining elements (L1, C5 and C6) form a simple LC tuned oscillator. The inherent problem with this type of circuit diagram transmitter is that any external load (antenna) will change the operating frequency.

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FM Transmitter Circuit with MAX2606

FM transmitter schema which is build using single chip of MAX2606. A very simple FM transmitter connects your home-entertainment system to a portable radio that will be carried surrounding the house and into the back yard. As an example, it is possible to play music on the CD player in your private room, and listen to it on a portable radio by the back-yard barbeque.



IC1 is a voltage-controlled oscillator with integrated varactor. Its nominal frequency of oscillation is set by inductor L1, and a 390nH value places that frequency at 100MHz. Potentiometer R1 then allows you to choose a channel by tuning above the FM band of 88MHz to 108MHz. Output power is about -21dBm into 50 (most nations accept emissions below 10dBm in the FM band).

The home systems left and right audio signals are summed by R3 and R4, and attenuated by the (optional) potentiometer R2. R2s wiper signal serves as a volume adjustment by modulating the RF frequency. Signals above 60mV introduce distortion, so the pot attenuates down from that level.

In the absence of a common FM radio antenna, 75cm (30 inches) of wire will suffice as a transmitting antenna. For most effective reception, it need to be mounted parallel with the receiving antenna. The IC operates on a single power supply voltage inside the range 3V to 5V, but it is best to regulate the applied voltage to reduce frequency drift and noise.

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Simple FM transmitter with 2N3904

In this section discuss about the series of mini fm transmitter, with broadcast coverage of about 300-400 meters. when using a 9 volt working voltage, the transmit power of about 300 meters and when using the working voltage 12 volts, the range of about 400-450 meters, depending on the antenna you use.

This scheme of simple fm transmitter

For L1 and L2 windings 5 times the wrap, you can use a pen to fill melilitnya so neat and after lepaslah content of these pens. C5 is used for placement of broadcasting frequencies, can be tuned between 88-108 mhz, to reach further use steering antenna or Yagi antenna.

Part List

C1 = 0.001uF

C2 = 5.6pF

C3 = 10uF
C4 = 10uF
C5 = 3 - 18pF Adjustable capacitor

R1 = 270R

R2 = 4.7K

R3 = 10K

R4 = 100K

R5 = 4.7K

R6 = 4.7K

Q1 = 2N2222A

Q2 = 2N3904

L1 = 5 turn

L2 = 5 turn

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FM adaptor circuit for car stereo

With this compact FM adapter schema plugged into the audio out of your cassete player or i Pod out put,you can listen your favorite music on your car stereo.This schema is very useful if your car stereo does not have an auxiliary in socket.The schema is nothing buy an short range FM transmitter.





The FM transmitter schema is based on low power NPN transistor 2N2222.The tank schema consisting of L1 & C1 produces the necessary oscillations at the collector of Q1.The capacitance C4 , resistance R3 & R4 performs the function of mixing the stereo out put from the audio player or i-Pod.The emitter resistance R2 provides sufficient stability to the schema.It also limits the collector current to increase the battery life.



Notes.

* Use a 28SWG , 10 cm insulated copper wire as antenna.
* For L1.make 8 turns of 20 SWG insulated copper wire on a 5mm dia plastic former.
* Power the schema from a 3V battery.
* Assemble the schema on a good quality PCB or common board.
* C1 can be a 50pF trimmer.

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