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1、袖珍fm电调谐收音机的制作（Fabrication of pocket FM electrically tuned radios）FM pocket electric tuning radio.Txt51 is an inexhaustible source of self-confidence, self-confidence is surging waves, confidence is the jet stream ahead of the channel, self-confidence is the real mother of success. The whole pie cont
2、ributionDoc document may at the WAP end of the browsing experience poor. Suggest you select TXT, or download the source file to the machine view.TDA7088TMaking FM pocket electric tuning radioThis paper introduces the FM pocket computer selected radio using TDA7088T integrated block PHILPS company de
3、velopment and production, with a 16 foot dual flat package, the working voltage is 3V, the circuit consists of FM radio from the antenna to all function discriminator output audio signal, the search is also provided with a tuning circuit, signal detection circuit, and squelch circuit compression in
4、frequency offset frequency locked loop circuit FLL. Intermediate frequency TDA7088T circuit design for 70kHz, the peripheral circuit without intermediate frequency transformer, which consists of frequency selection circuit inside the RC filter to complete. This machine is like a digital radio that u
5、ses electric tuning button (RUN), the other is a reset button (RESET). The circuit is switched on, click the search button, the circuit automatically from low to high frequency radio search, once the search to radio signals, automatic stop tuning. If you then click the search button to search the ci
6、rcuit to the high end station. When the FM receives the highest frequency tuned to the end, just click the reset button, the vibration frequency is returned to the low end, search and start tuning. The manufacture and the debugging method of the machine. This machine adopts the headset wire as an an
7、tenna, the FM signal from the headset line sensed from TDA7088T integrated block 11 feet into the mixer circuit, 70kHz intermediate frequency signal and the local oscillator mixer. The radio signals into the integrated block 11 and 12 pins, L2, C10, C11 inductance capacitance, C12 input circuit, the
8、 circuit of the frequency by L1, C5 and D1 decided to varactor. It can be seen from figure C1 for C6 squelch capacitance, frequency feedback capacitor, C7 low-pass capacitor, 15 pin to search tuning input, C14 capacitor, 16 pin electric tuner, AFC output. When assembled in accordance with the circui
9、t diagram, the components are welded to the circuit board. Here we need to pay special attention to the two hollow coil, a small number of rings is the oscillating coil that is installed between 4 and 5 feet of the integrated block, another turns is the input tuning circuit coil is installed between
10、 the 11 and 12 pin, due to very low frequency selection, the vibration signal is easy to end went to the circuit caused by interference from the antenna input, so that the position of the coil to be placed into two mutually perpendicular. Welding should pay attention to TDA7088T pin arrangement dire
11、ction, not a mistake, welding electric iron shell to the ground, do not power on the circuit board under the condition of welding on the circuit board components. After installation, should check carefully and avoid wrong welding, weld and short circuit and so on, after the confirmation for the next
12、 step of debugging. General factory mass production is used to debug sweeptester radio amateurs without these instruments can be used to debug the high frequency signal generator, also available in the local radio station FM to debug.Cover with a DC power source to the 16 pin up radio frequency, the
13、 DC power supply voltage to Vcc0.1V value (such as the power supply of Vcc=3V radio is transferred to 30.1=2.9V), a spacing or adjust the oscillation coil inductance of the received radio signal of 87 5MHz, and then transferred to the Vcc1.6V near value voltage DC power supply as long as you can, yo
14、u can receive 108MHz signal. Frequency coverage well adjusted, get rid of the DC power supply, assembly debugging. The machine receives the frequency in the range of 88 108MHz (due to SC1088 integration with TDA7088T chip and pin performance, can substitute each other directly). See the circuit show
15、n above. Special specifications can be the machine to receive the frequency of 76 106MHz, the volume is only 78mm * 44mm * 14mm.Main features:D7088 search circuit is provided with a tuning circuit, signal detection circuit, control circuit and frequency locked loop (FLL) circuit.Intermediate frequen
16、cy D7088 circuit for 70kHz peripheral circuit without intermediate frequency transformer, which consists of frequency selection circuit inside the RC filter to complete.In the tuning mode, D7088 can use the traditional mechanical tuning variable capacitor, but also to search by radio tuning way like
17、 digital radio. In the tuning, only need to operate search tuning button (RUN), the circuit automatically from low frequency to high frequency radio, once found search to radio signals, automatic stop tuning. When the FM receives the highest frequency tuned to the end, just click the reset button (R
18、ESET), the frequency of return to the most low-end, search tuning and start again. Terminal function symbol function squelch output symbol MUTE terminal number 9 IF input functionTerminal number 12345678The audio output power of the vibration AF loop filter tuning loop feedback IFVoAF LOOP Vcc OSC I
19、F FB10111213141516IF limiting amplifier low pass capacitor RF signal input RF signal input offset voltage limiter capacitorLow pass CLP1 IF VoIF 1dB output capacitance amplifierAllpass filter capacitor tuning input search tuning, AFC outputThe two key behavior often seen in our daily life (the key t
20、uning, one button reset type) automatic tuning of FM radio, designdiverse, many gifts and gifts are also using it. It can be made with a potentiometer tuning by FM radio. The original circuit diagram as follows:If the circuit board is in good condition, can use the following method: 1. 5.6K transfor
21、mation resistors and two key switch of the circuit board on the 16 feet then removed, foot on the ground. Sixteen2. find a potentiometer, 10K, 20K, 50K, resistance can be 100K. It will be the end of the 3. sliding potentiometer terminal of the circuit board on the varactor, the other end is connecte
22、d with both ends of the 3V power supply, the other end is connected to the ground. Well, after these three steps, a potentiometer is electrically tunable FM tuner OK. If you want to drive a loudspeaker pronunciation, add a power amplifier.The following figure circuit changes:Radio: desktop FM radio
23、TDA7088T:The radio part: basically the original circuit board, the PCB board will do after taking off the original plate device on the PCB board to produce their own. Note: in the production of PCB board must pay attention to TDA7088TBottom welding on the circuit board, the figure of the device is r
24、otated 180 degrees in the design of PCB board, the board can not be used or made. Part I: power amplifier power amplifier using TDA2822M film. This film voltage range wide, 1.8V 15V; high output power (compared with IC), connected bridge output 6V power supply in 8 load can reach 1.35W; the external
25、 circuit is simple, if not connected to the load correction network, peripheral circuit only 3 components, which will improve the success rate of production. With the existing power supply part: a 10V/8W output transformer, rectifier power for power amplifier, regulated power supply with the radio p
26、art, using three terminal adjustable regulator IC LM317, adjust the output voltage in the 3V. If the regulator IC 3.3V on hand, can make the circuit more simplified.Pictured above is the whole circuit diagramThe adjustment: any production must be adjusted, in order to achieve the desired purpose, th
27、is machine is no exception. The adjustment is mainly the tuning range, the voltage at the ends of the varactor diode with higher capacitance it is, the lower voltage is less. To make the change of varactor diode junction capacitance to frequency range of 108MHz FM radio coverage to 88, the voltage a
28、cross the diode can reach 2.2V is enough. If it can be extended to 118MHz 3V. In order to make the potentiometer adjustment right in the FM broadcast band range, making it the voltage range within 2.2V, so that the tuning becomes convenient, radio could be more accurate. In order to achieve this goa
29、l, in the end of the potentiometer connected in series with a resistor, the resistance of the resistance value of the potentiometer 1/2 optional. For example, with the optional 5.1K 10K resistance potentiometer, 20K potentiometer optional 1 0K resistance and so on. I use the 22K potentiometer, the s
30、elected resistance is 15K. To be more precise, I do: in the end the 22K tuning potentiometer is connected in series with a 22K potentiometer, tuning potentiometer to head (the most high-end FM band) and then slightly callback point, then adjust the potentiometer to the radio series, received FM sign
31、al of a local high-end, a FM here is the most high-end 107.5MHz, can receive the Taiwan basic frequency coverage is well adjusted. Then the series potentiometers removed, measure its resistance, find the fixed resistor in series with resistance of close to the end of the tuning potentiometer, so eve
32、n if the well. The low-end basically can be covered, and often have surplus. If not covered, oscillation coil can adjust the TDA708 8T integrated circuit 4, 5 connected to the two ends of the coil inductance change can. In general, the low-end adjustable inductance cover adjustment radio frequency,
33、and adjustable end adjustable capacitor, summed up in one sentence is: the low-end high-end adjustable inductance adjustable capacitor.The inductance and capacitance are oscillation channel in components.TDA7088 and TDA2822 radio integrated chip Holland PHILPS company, which TDA7088 is electrically
34、tunable FM receiver integrated circuit, TDA2822 low power dual channel power amplifier integrated circuit. With the headset as the radio antenna, has the advantages of small size, less external components, high sensitivity, stable performance, low noise, high degree of separation, preparation and ch
35、aracteristics of simple debugging. This is radio two FM band: A band (76 88MHz) and B band (88 108MHz), the A band transmitter dedicated to receiving school programs, such as many universities are now playing the English program, there are four and six grade English listening test for the radio rece
36、iver. The B band can receive normal FM programs. TDA7088 T uses a low intermediate frequency technology advanced, cancel the intermediate frequency transformers, ceramic filter, antenna input frequency modulation circuit, eliminating the vibration level of the variable capacitor, and internal set up
37、 automatic station search and squelch function, so the peripheral components reduced a lot compared with other radio.As shown in Figure 1 for FM electrically tunable radio circuit. The working principle and signal process are briefly described below the radio circuit.Figure 1 FM electrically tunable
38、 dual band radio circuitThe power, by induction headset to a FM signal, the signal from the TDA7088T pin 11 input to the integrated block, with high discharge, mixer, amplifier, frequency, low discharge, get the stereo composite signal, through the squelch switch from 2 feet output via R2, R3, C15,
39、C20 component of the compensation network after the potentiometer RP to fetch a pressure, give TDA2822M 7By foot, TDA2822M power amplifier, the output from 1 feet, the C23 audio signal coupled to the headset, the headset sound driver.Station search, press the search button S1, RS trigger TDA7088T in
40、ternal S end is placed in the 1 trigger control, constant current source charging capacitor C7, voltage C7 at both ends of the rising. This voltage by R1, diode BB910 is added to the variable oscillator circuit, the frequency change and tuning. When the received broadcast signal, signal detection ci
41、rcuit outputs high level, RS triggers the end of R is 1 flip flop, a constant current source, by the end of the C7, charging at the same time, trigger control, constant current source to start charging C7 controlled audio output, automatic frequency control, the lock listen to the program. When pres
42、s the reset button when the S2 tuning voltage at both ends of the C7 is discharged, the vibration frequency to the lowest frequency.Sc1088tThis paper introduces the FM pocket computer selected radio using SC1088T integrated block PHILPS company development and production, with a 16 foot dual flat pa
43、ckage, the working voltage is 3V, the circuit consists of FM radio from the antenna to all function discriminator output audio signal, a search tuning circuit, signal detection circuit, squelch circuit and the compression frequency offset frequency locked loop circuit FLL. Intermediate frequency SC1
44、088T circuit design for 70kHz, the peripheral circuit without intermediate frequency transformer,The frequency selection is accomplished by the RC intermediate frequency filter in the circuit. This machine uses the electric tuning button (RUN) as the digital tuning radio, and the other is the reset
45、button (RESTE). When the circuit is connected with the power supply, press the search button, the circuit automatically searches the radio station from the low frequency to the high end. Once the radio signal is searched, the tuning is stopped automatically. If you press the search button again, the
46、 circuit continues to search the high frequency side of the radio. When tuning to the highest end of the FM receive frequency, just click the reset button, and the local oscillator frequency is back to the lowest point, and the search tuning begins again. The following describes the method of making
47、 and debugging the machine. The machine adopts an antenna, and the FM signal induced by the antenna enters the mixing circuit from the SC1088T integrated block 11 pin, and then generates the 70kHz intermediate frequency signal with the local oscillator mixing. The radio signal is sent into the integ
48、rated block 11 and 12, and the inductance L2, the capacitance C5, the C6 and the C12 constitute the input circuit, and the frequency of the circuit is determined by L3, C14 and varactor diode D1. It can be seen from figure C12 for C15 squelch capacitance, frequency feedback capacitor, C19 low-pass c
49、apacitor, 15 pin to search tuning input, C10 capacitor, 16 pin electric tuner, AFC output. In assembly, the components are soldered to the circuit board in accordance with the wiring diagram. Here we need to pay special attention to the two hollow coil, a small number of rings is the oscillating coil that is installed between 4 and 5 feet of the integrated block, another turns is the input tuning circ