"5W FM transmitter production, FM Transmitter
Keywords: 5W FM transmitter production
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The Veronica FM transmitter is easy to make, stable performance, pure signal, no professional parts and ICs, and auxiliary testing enables you to debug in the case without professional equipment. It has two versions, 1 watt and 5 watts. 1 watt version is suitable for 3 kilometers of emission distance, the power supply required is 12-16V 200mA; 5 watts of version is suitable for 8 kilometers of emission distance, the required power supply is 12-16V 900mA. This article introduces 5 watts.
Figure 1: 5W Veronica line diagram
The transmitter comes with a mixer that allows you to simultaneously transmit an audio signal from the CD and the microphone. Transistor T1 is a microphone amplifier, variable resistors R1, and R2 adjustment volume (see debug sections). A oscillator is an oscillator between R8 and C21, which is a component that generates a radio radio frequency signal. Diode D1 is a so-called "variable tube", which corresponds to a tonable capacitor, which is controlled by audio signal, changing the oscillation frequency of the oscillator, and functions. C12, C13, and L1 determine the frequency of the oscillator. This oscillator is actually composed of two reverse oscillators, each running near 50MHz, and when two signals are combined, a 100 MHz signal is formed. This circuit is much stabilized than a single 100 MHz oscillator. The signal of the oscillator is amplified from T4, T6 to 5W. The circuit on the right of T4 includes antenna impedance matching and low pass filtering. The circuit composed of D2, D3, and T5 is the auxiliary debug, which samples the signal of the radio frequency output, controls the light emitting diode D5, and the D5 is also bright.
This circuit itself does not with a stereo modulator, if you need to play a stereo program, please refer to the stereo modulator here.
Component list
Resistance:
R1 + 2 10K adjustable R3 820K R4 4.5K R5-7 220 R8 1.5K R9 15K R10 + 11 1K R12 33K R13 + 14 56 R15 + 16 68K R17 47 R18 270 R19 10 R20 22 R21 1.5K R22 270
capacitance:
In addition to special designation, use ceramic or mica capacitors. C1, 2, 7, 16, 17, 19, 24, 29 and 31 n C3-5 and 8 10U 16V electrolysis C6, 18 and 30 220U 16V electrolysis C9, 10 and 20 10N C11 22P * C12 47P * C13 22P fine-tuning C14 And 15 15p * C21, 25 and 266P Try C22 100P C23 15P C24 33P C27 1.8P C28 5.6P C32 and 34 47P C33 22P C35 and 38 1N C36 220N C37 100P * C11, 12, 14 and 15 Decideting the oscillation frequency, the most It is easy to use high quality mica capacitors. Coil:
Use no skeleton hollow type. Wires on a refill or other round rod in a wire having a diameter of 1 mm, and then carefully elongate to the correct length, and determines the two ends of the coil as shown in FIG.
L1 6 coils, each 2 in diameter 5mm, length 5mm L2 3 匝, 7mm in diameter, 7mm L3 3, inner diameter 6mm, length 8mm L4 in 2.2k carbon rod resistance (diameter about 2 mm) on 14 The joint line of 0.2 mm in diameter, on the joint of the end weld resistance of the enameled wire. A magnetic beads in each of the two connections of the resistor, as shown in Figure 2b. L5 5, 6mm inner diameter, 11mm L6 4, 6mm inner diameter, 9mm long
RF Choker (RF Choke):
The choke (H1-4) can be used in a magnetic beads of 4 mm in diameter of 0.5 mm, 5 mm long. Note that the enameled line should pass from the hole of the magnetic bead, and the magnetic bead should use the operating frequency at 100 MHz material (usually No. 43). If the magnetic bead is not found, it can be made by the method: in the 33K carbon bar resistor, the packed line of 0.5m diameter is 0.2mm, on the joint of the end solder resistance of the lacquerable line.
H1 magnetic beads 5 H2 magnetic beads 1 H3 magnetic beads 2 h4 magnetic beads 3
Diode: D1 is preferably used in pair, that is, two symmetrical variable tube back to back, the middle is negative; however, this is not very important, and two general variable tube can be used. D1 KV1310 D2 + 3 1N4148 D4 General Lighting Diode D5 1N4001
Three-stage tube: T1 + 5 BC548, general small signal triode T2 + 3 BF494, high frequency small signal triode T4 radio frequency power pipe 2W, 12V, 10DB @ 175MHz 2N4427, C2538, C1970 3DA190, 3DA194, etc. T6 radio frequency power tube 4W 18V> = 10dB @ 150MHz MRF237, 2N3926, C1971, C1947, MRF630, BLU99, 3DA21, 3DA106, 3DA56 3DA192, 3DA22, etc.
Note: The pin position of the power tube of other signals may differ from Figure 8.
I1 is a 5 volt regulator that provides a constant voltage to the D1 to maintain the frequency of the transmitter. I1: 78L05 (or 7805) Other: Circuit Box BNC RF Out Insert 2 x 3.5mm Audio Infographic Power Skation 9-16V Power Atenna Microphone CD Machine or Recording
assembly
RF circuits are quite sensitive to coarse circuit boards, including wiring, grounding, position, etc.). It should be avoided using a bread board; the two-sided circuit board using the ground is preferably used, but the design of Figure 4 is filled with a general trail in the general trace, which is also very good to use a single-sided circuit board. Components should be placed on the circuit board as much as possible with the shortest wire. The transmitter should be mounted in a metal shield (such as a cast aluminum box), while the metal box is connected to the circuit. A 3mm thick bolt with a 5-10 mm long support column can be used to achieve a good connection of the metal box on the circuit board. Transistors T4, T6 require a heat sink to cool. The radiator of T4 can be done with a slightly small inner diameter than the transistor, a metal tube of 2 cm long. A slot is cut on the tube to make the holes becomes larger and enclosed on the transistor. The heat sink required for the output tube T6 can be made of a L-shaped aluminum strip of approximately 14 cm long, 2.5 cm wide, 3 mm (see Figure 10), or a special 5W heat sink. The wells of the fixed T6 should be as accurate as possible; you can open a slot on the heat sink in the illustrated, carefully insert the heat sink, the radiator will ensure the transistors and radiators. Good contact. Some thermal conductors such as silicone oil can be applied in the middle of the transistors and radiators. The heat sink is fixed to the PCB with a screw and clipped between the PCB and the heat sink. Note: The housing and collector of the radio frequency power tube are connected (related to the model of the three-stage tube), in which case the heat sink should be insulated from the ground or shielding box (distance from approximately 5 mm). The pin position of the other model of the power tube may be different from Figure 2, Figure 3. Turn some holes on the lid to ensure air circulation.
Microphones and CD input interfaces can be used with 3.5mm earphone sockets, and the power supply can also be used with similar sockets. For antenna output, we recommend the F-type socket for BNC sockets or television machines (original products with n-type sockets). The genus of the socket should be connected to the metal shield box and the internal wire should be as short as possible. You can embed D5 on the lid so you can often check if this transmitter works normally.
Be
The power supply Veronica 5W transmitter uses a DC power supply from 9 to 16 volts; preferably 5W power, power consumption of about 900 mA (related to RF power amplification tube T6). If the power supply is poor, the radio frequency of the radio will instably or will transmit a "嗡" communication sound. If you plan to use a battery or a rough power supply, an additional regulator circuit should be added, such as replacing D4 with 7812 or 7815 (see above Figure 1). For 78xx type regulator circuit, XX is an output voltage, such as 7815 is 15V, and the capacitance in parallel is greater than 10nf.
The launch antenna of the antenna radio is particularly important, please refer to the special introduction here.
Debug In order to make the transmitter normal efficiently, some simple debugging is required. Use an antenna "false load" instead of an antenna when debugging, which helps you distinguish between the main transmit signal and the weak harmonic signal while ensuring that you do not emit the debug signal widely. The production method of false load is to receive a 47 or 68 ohm carbon rod resistor (corresponding to the antenna impedance you plan to use) to a BNC or N-type antenna socket; determine that this resistance can withstand the power from the transmitter ( 5W) and is not wiring. If you can't find a 50 ohm 5W carbon rod resistor (can not be wired), 3 150 ohm 2W resistance or 5 250 ohm 1w resistors can be paid in parallel, as shown in Figure 2b.
Tune all of the fine-tuning capacitance to the intermediate position (half of the upper plate covers the lower portion), connect the antenna fake load to the antenna output jack, and connect a CD player to the CD input socket. At this time, the light-emitting diode D5 should be bright (if not, try adjusting C21), and the transmitter should work around 98MHz. Use a small screw knife with an insulated handle to adjust the C21, 25 and 26 to make the light emitting diode to the brightest. Then adjust the transmit frequency as follows: slowly adjust the C13 (direction to the frequency of the frequency you want to use) until the light emitting diode is bleak, but not completely destroyed; then adjust C21, 25 and 26 until the LEDs are brighter; This is repeated until you get the frequency you want. Now use a FM radio to check if you only transmit signals on one frequency, if not, you may have to re-adjust. If you cannot adjust to the end of the FM broadcast band (88-108MHz), you need to change L1: Carefully press the coil to adjust the low frequency, or increase the spacing of the coil to adjust the high frequency; and ensure that the six coils of L1 Is the same, otherwise it will affect the purity of the transmitted signal. According to our test results, the transmit frequency of the circuit may change 50-70 kHz during the transmitter to the internal temperature, so that the adjustment of the transmit frequency is maintained until the transmitter is stable (about 10-30 minutes) precise.
Now adjusting R2 until the sound of the disc player is as large as the general professional radio. It should be noted that some radio uses "compression" technology to achieve the effect of sounding sound than it actually sound, if you also set up so big sound, you may lead to excessive modulation and interfere with nearby channels, this is to avoid . You have to carefully do not set the microphone sound too much, it is best to use an external sound mixer with automatic gain control.
After adjustment, the fake load is replaced with a transmit antenna. In general, the transmitter will work normally, but also adjust the C21, 25 and 26 and the length, position, angle of the antenna to achieve maximum transmit power, small amplitude. The ground adjustment C13 makes the transmit frequency accurate. In order to avoid being discovered, the earphone of one FM radio can be output to the transmitter, and the signal of one FM station is used as a test signal with the signal of one FM station. Do not try to open a transmitter without the antenna load, which will damage the output transistor; turn the power supply to the launch antenna. "
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