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 circuit are collected in a single IC. When taken together with the other accessories minimal, then 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 tuner to use quite complex.
The working of circuits
This circuit is to create a simple, no hassle, use the equipment less. Important part in the TDA7000 IC which acts as 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, Quardrature Demodulator FM Detector,Phase demodulator, Mute detector, Mute switch
– The antenna as the receiver through C1 to the band pass filter circuit, is L1 to pin 13 and 14 of IC1.
– The capacitor C2 is a D-Coupling Signal,
– The capacitor C5-C10 are a frequency filter to amplifier circuit.
– Pin 6 is used to tune the station. With C11, VC1 and L2 combination, to select for 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 ground.
– The pin 2 is output of 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 need 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 as shown in Figure 2.
The L1, use No. 18 enameled copper wire, wrapped around a core diameter of 3 mm, 23 rounds, then pull the core out.
For The L2, we use the number 24 enameled copper wire, wrapped around 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 a 2 feet instead.
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.
When built circuit is finished, but device does not work. If you are sure, where to place the equipment does not crash, according to the following guidelines.
1. No signs of any sound come out. C13, C15, VR1 may lack, C12, C14 may be short or IC may be damaged.
2. Reception only 1-2 stations, The trimmer (VC1) may be missing or damaged.
3. Can not get a signal, but sound is distorted. try to check some C ceramics, may leak or deteriorate.
4. 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 connected to the amplifier. If the a very loud voice is to use a high power amplifier. If listen are not cold hearted play, just uses low-watt amplifier. At affordable prices perform well.