If we want to build or learn about the FM receiver circuit. It has many circuits to do. But now I will show you two circuits ideas.
The first is a very old circuit, using only transistors. And the other one, using IC chip.
Even both circuits are small FM radio receiver circuit. But works well, although the sensitivity is poor.
Old FM receiver circuit using transistor
This circuit is suitable for learning only. See in the circuit below.
The principle of this circuit is to use the generator frequency circuit. Which consists of Q2 and Q3. They work by producing frequency sync with the frequency that has been derived.
Then, Q1 acts as a preamplifier of the frequency VHF range wider. We may cut the Q1 out. Then connect the antenna at the C4. But the sensitivity of this circuit will decrease.
Figure 1: FM receiver circuit using transistors
Next, we can adjust the C5 in the frequency generator circuit. To control the frequency from 87MHz to 108 MHz.
And the frequency of the incoming sync with the frequency of the generator itself. Therefore, the frequency deviation of the signal received from the antenna to the audio signal.
Which the frequency modulation is across the VR1 + R5. And the low pass filter circuit, R6/C6 be the frequency of sound. Then, after be amplified by the Q4 and Q6, and enter to output by C9 respectively.
Details of Coils
Wrap 25 SWG enamel coated copper wire on an air core of 10 turns, with an inside diameter of about 3 mm.
13 turns of 25 SWG inside diameter of about 3 mm.
4 turns of 18 SWG inside diameter of about 5 mm.
FM tuner circuit using TDA7000
Currently, I am cheering for you to try out the finished IC. It’s easy and economical. Plus it’s also quick to create and easy to customize.
See the circuit below.
In the old days, common people will build radio receivers FM, himself, as very difficult, and once completed, also low efficiency.
But now, the complexity of these circuits are collected in a single IC. When taken together with the other accessories minimal, they can receive a clear FM frequency.
The FM tuner circuit is radio receivers, which receive signals from radio stations.
For the tuner, which will be presented at this time, as small radio receivers. But is not less than the old tuner to use quite complex.
How the FM tuner circuit works
This circuit is to create a simple, no hassle, use the equipment less. The important part in the TDA7000 IC which acts as a receiver of radio FM has a few accessories so this tuner is small.
– Internal the integrated circuit TDA7000 includes: R.F. input stage, Mixer, Local oscillator, I.F. amplifier/limiter, Quadrature Demodulator FM Detector, Phase demodulator, Mute detector, Mute switc
The circuit of Cheap FM tuner by TDA7000
– The antenna as the receiver through C1 to the bandpass filter circuit, is L1 to pin 13 and 14 of IC1.
– The capacitor C2 is a D-Coupling Signal,
– The capacitor C5-C10 is a frequency filter to the amplifier circuit.
– Pin 6 is used to tune the station. With C11, VC1 and L2 combination, to select the desired signal.
– Pin 16 to the negative power supply terminals.
– And Pin 5 to positive power supply terminals, by pass-through R1, C3 both are the voltage filter.
– The capacitor C4 is bypass high frequency down to the ground.
– The pin 2 is the output of the circuit, have R2 and C12 both as act DM pasis signal pass through to C13
– The VR1 adjust the sound pass through C15 to the output, this output needs to joint with power amplifier circuit to use next.
How to build
First of all, prepare the device is ready. After that, the PCB copper pattern
How to make L1 & L2
- The L1
Wrap No. 18 copper wire around a core diameter of 3 mm, 23 rounds, then pull the core out.
- The L2,
Wrap No.24 enameled copper wire on a core diameter of 3 mm to 6 rounds, then pull the core out.
We put down the first resistor. Then, place the IC socket L1, L2, C, VR, and VC1, respectively, for L1, L2, we have to a leg to scratch the coating solution is removed first. And then solder all the complete. For the antenna, if the antenna is not, it may be difficult to wire on 2 feet instead
PCB copper layout of the TDA7000 FM tuner circuit.
The Component layout of FM tuner circuit using TDA7000
The shopping lists
0.25W Resistors, tolerance: 5%
C1: 100µF 16V
C13,C15: 1µF 16V
C1: 220F 50V (221)
C2,C4: 0.047µF 50V(474k)
C5,C10: 0.033µF 50V(332k)
C6: 0.1µF 50V(104k)
C7, C8: 330pF 50V(331)
C9,C14: 0.01µF 50V(103k)
C11: 30pF 50V(103k)
C12: 0.001µF 50V(102k)
Customization of FM tuner circuit
Bring output of the tuner circuit connected to the input of the amplifier, Then? the power supply to the circuit which uses energy from 4.5V to 9V. VR1 adjusts the position of the maximum, and then gradually turn the volume of the amplifier, Hear the speaker, Try to rotate the VC1 and FM tuning. If not, try to get at G spot of VC1 (it is written on the trimmer). Until can get the wave, the end of the tune.
- FM wireless transmitter circuit
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- Wideband Active Antenna amplifier circuits on SW/MW/FM
When we build circuit is finished, but the device does not work. If you are sure, where to place the equipment does not crash, according to the following guidelines.
- No signs of any sound come out. C13, C15, VR1 may lack, C12, C14 may be short or IC may be damaged.
- Reception only 1-2 stations, The trimmer (VC1) may be missing or damaged.
- It cannot get a signal, but the sound is distorted. try to check some C ceramics, may leak or deteriorate.
- At pin 5 of IC1 R1 has no power that may be lacking C3, C4 is short.
When refining tuner until the device completely. May have a box to put it beautifully. To connect to the amplifier. If the very loud voice is to use a high power amplifier. If listen are not cold-hearted play, just uses the low-watt amplifier. At affordable prices perform well.
I love electronic circuit. I will collect a lot circuit electronic for teach my son and are useful for everyone.