“I just looked up the data sheet for the BF494 at Philips, and noted that the Collector and Base in your diagram seem swapped. Why is the Vs via C6 going to the ground?” “I have tried to build the project but it didn’t work out, and it doesn’t compare with the datasheet of the LM 386. Even after adjusting the potentiometer and variable capacitor in various positions, no sound is emitted from the eight-ohm speaker.Īlso, I noticed quite a few questions unanswered on this thread that could potentially provide people with solutions The inductor is a 24AWG Enameled copper wire consisting of 12 loops, each being 4mm in diameter. The 2N3707 was used in place of the BF495 because in a previous question you stated a BF494 will work in place of a BF495. For both transistors, the 2N3707 was used which is equivalent to the BF494. Everything was done as shown on the schematic with the exception of the transistors and inductor. Connections have been thoroughly checked in comparison to the schematic above. I’ve completed this project on a protoboard and it doesn’t seem to work. More on FM receivers in the slideshow below. The receiver can be operated off a 6V-9V battery. The 22k volume control (VR) is a logarithmic potentiometer that is connected to pin 3 and the amplified output is obtained at pin 5 of IC LM386. It provides 1 to 2 watts, which is enough to drive any small-size speaker. IC LM386 is an audio power amplifier designed for use in low-voltage consumer applications. The performance of this tiny receiver depends on several factors such as quality and turns of coil L, aerial type, and distance from the FM transmitter. You can also Read: Different Types of Antennas The optimum length of copper wire can be found experimentally. However, A good reception can also be obtained with a piece of isolated copper wire about 60 cm long. You can use the telescopic antenna of any unused device. When the required number of turns of the coil has reached, the coil is taken off the cylinder and stretched a little so that the turns don’t touch each other.Ĭapacitors C3 (100nF) and C10 (100♟, 25V), together with R3 (1k), comprise a band-pass filter for very low frequencies, which is used to separate the low-frequency signal from the high-frequency signal in the receiver. It can be constructed on any cylindrical object, such as a pencil or pen, having a diameter of 4 mm. The self-supporting coil L has four turns of 22 SWG enamelled copper wire, with the air core having a 4mm internal diameter. Its capacitance is to be determined experimentally.
#Two transistor fm receiver full#
If you are using some other capacitor that has a larger capacitance and are unable to receive the full FM bandwidth (88-108 MHz), try changing the value of VC. So, a 22pF trimmer is a good choice to be used as VC in the circuit. You should be able to change the capacitance of the variable capacitor from a couple of picofarads to about 20 pF. The information signal used in the transmitter to perform the modulation is extracted on resistor R1 and fed to the audio amplifier over a 220nF coupling capacitor (C1). That is, it has to be tuned between 88 and 108 MHz. Trimmer VC sets the resonance frequency of this oscillator to the frequency of the transmitting station that we wish to listen to.
Transistor BF495 (T2), together with a 10k resistor (R1), coil L, 22pF variable capacitor (VC), and internal capacitances of transistor BF494 (T1), comprises the Colpitts oscillator.
Here’s a simple FM receiver with minimum components for local FM reception. Presented below is an FM Radio Circuit Diagram along with its full explanation. This allows a much larger range of frequencies to be transferred in FM and thus the quality of FM transmission is significantly higher than that of AM transmission. The maximum audio frequency transmitted in FM is 15 kHz as compared to 4.5 kHz in AM. The FM radio transmitter has a 200kHz wide channel. This bandwidth range is marked as FM on the band scales of radio receivers, and the devices that are able to receive such signals are called FM receivers. FM Frequency Rangesįrequency modulation is used in a radio broadcast in the 88-108MHz VHF frequency band. It is also used in telemetry, radar, seismic prospecting, and monitoring newborns for seizures via EEG, two-way radio communication systems, music synthesis, magnetic tape-recording systems, and some video-transmission systems.Īn advantage of frequency modulation is that it has a larger signal-to-noise ratio and therefore rejects radio frequency interference better than an equal power amplitude modulation (AM) signal. Frequency modulation is widely used for FM radio broadcasting. Of the radio waves, FM is the most popular one.
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