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Showing posts with label fm. Show all posts

Tuesday, April 30, 2013

FM Stereo Transmitter

Youll 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.

Circuit Diagram

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 bring the level down. You can balance the signal by using headphones. The inductor L1 is 3 turns of .5 mm wire on a 5 mm ferrite core.

Sourced: extremecircuits

Tuesday, April 9, 2013

FM transmitter using UPC1651

Here is the circuit diagram of an FM
transmitter using the IC UPC1651. UPC1651 is a wide band UHF Silicon
MMIC amplifier. The IC has a broad frequency response to 1200MHz and
power gain up to 19dB.The IC can be operated from 5V DC.
The audio
signals picked by the microphone are fed to the input pin (pin2) of the
IC via capacitor C1. C1 acts as a noise filter. The modulated FM
signal will be available at the output pin (pin4) of the IC. Inductor
L1 and capacitor C3 forms the necessary LC circuit for creating the
oscillations. Frequency of the transmitter can be varied by adjusting
the capacitor C3.Circuit diagram with Parts list.

Notes.

The circuit can be assembled on a Vero board.
Inductor L1 can be made by making 5 turns of 26SWG enameled copper wire on a 4mm diameter plastic former.
A ¾ meter insulated copper wire can be used as the antenna.
Do not give more than 6V to the IC.
Mic M1 can be a condenser microphone.

FM Moulator with IC 555

FM Modulator circuit is a simple FM modulation circuit using IC 555, where the resulting modulated signal has a tenuous meeting depends on the signal frequency information.

The resulting signal can be spelled out quite nice and stable so that the result will be more perfect. No winding or inductor in series modulator, so you do not need to bother to make a winding and calculate the value of the coil that you created it. With this circuit the desired value of frequency modulation can be obtained easily by calculating the frequency of IC 555 in general, which is determined by the resistor 6.8 K and 3.3 K and 0.1 UF capacitor. To obtain the other frequencies of your stay replace one or all three components.

Actually fm modulator ic 555 circuit is very simple though, but I think it reliable enough to handle a simple application purposes that do not require a big power or a very high frequency. But if you want more power you can add the RF amplifier circuit at the output of this circuit. Thus, the results of modulated signal can be amplified with the help of a series of supporters. In accordance with my experimental series modulators can work well at frequencies below the MHz range, because it is not IC IC 555 which is devoted to support of a very high frequency. You can use oscilltor transistor circuit, XTAL or others if you need a very high frequency.

The difference circuit with IC 555 on the multivibrator circuit in general is the use of pin 5, on the FM Modulator circuit is pin 5 of IC 555 is used as input information signal, which in turn will influence the shape of the output signal (modulated). But in applying this 5 pin multivibrator functions normally associated with 0.01 UF capacitor or left alone.

Thursday, March 28, 2013

Single Chip Stereo FM Transmitter Circuit

ROHM (www.rohm.com) is originally a resistor producer company, but finally expand their business and produce monolithic IC, and this one used in our circuit is the example. The internal structure of this FM transmitter integrated circuit consist of stereo modulator that creates a stereo composite signal, an FM modulator that modulate a carrier frequency with the composite signal, and an RF amplifier that provide enough power to be transmitted through antenna. This is the figure of the circuit;

The core of this stereo FM transmitter is BA1404 integrated circuit chip. from ROHM. This FM transmitter is ideal for wireless microphone, or for audio interface and distribution for home or car appliance. For example, you can now play your portable mp3/mp4 player on your old car radio sound system that doesn’t have line-input plug. This stereo FM transmitter chip is designed for 75-108 FM band, and you can adjust the operation by trimming the LC network connected to pin 10 of this IC chip. To ease the adjustment, you can use a 22-33p variable capacitor for the 15p capacitor connected to pin 10. Finally, this stereo FM transmitter works with only 1.5-3V power supply, ideal for battery operation. More than 3.5V supply voltage could burn this FM transmitter circuit. [Circuit diagram source: ROHM Application Notes]

Friday, March 22, 2013

FM Radio Transmitter schematic with pcb

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________________10-20 meters

Connector
X2-1________________Ground
X2-2________________VCC 9-12 Volts DC
X3-1________________Input
X3-2________________Ground

Thursday, March 21, 2013

Precise FM Tuning Indicator

Here is an add on circuit to your FM radio for precise tuning of stations. Usually an LED indicator is provided in FM radio to see whether the station is tuned or not. But it is difficult to see the precise tuning points since the variation in the LED brightness cannot be detected easily. This circuit solves the problem.

Precise FM Tuning Indicator Circuit diagram :

FM-TUNER Circuit diagram

The circuit uses the Op Amp IC CA3140 as a differential amplifier to sense the voltage level between the terminals of the tuning LED. The output of IC1 drives two LEDs one Red and one Green to indicate whether the station is precisely tuned or not. If both LEDs remain off, it indicates precise tuning. If anyone LED is on, it indicates that tuning is not precise. If both LEDs remain on, it indicates that there is no signal.

First tune the FM receiver in a station having strong signal. The tuning LED will light brilliantly. Then connect point A and B to the soldering points of the tuning LED observing polarity. Adjust VR till both the Red and Green LEDs turn off. Slowly change the tuning knob position. Any one LED will light up. So the circuit is working. Now glue the wiper of VR using adhesive to prevent its position change. Disconnect the tuning LED from the board. Now the circuit is ready to use. Power for the circuit can be obtained from the power supply of FM radio.

Source : http://www.ecircuitslab.com/2012/08/fm-tuning-indicator-circuit.html