Keywords: BH1417, FM emission circuit diagram
Author: Zhang Yiqiang
In addition to the stereo voice signals that can be broadcast, this small station can also modulate and transmit stereo signals such as computer sound cards, gaming machines, CD, DVD, MP3 players, mixers, etc..
The characteristics of the small station and the functional small radio have two microphones, and the recording of stereo programs can be realized. If a normal radio can realize the transmission and reception of a high-fidelity wireless frequency modified stereo signal. If there are two sets of such small systems, wireless FM stereo intercom functions can be implemented. In addition, the small station can be used for the development of wireless audio products such as stereo wireless speakers, wireless microphones, wireless headphones, notebooks. The small radio circuit board for making the completion is shown. From the figure, you can see that the structure of the small station is simple, compact, and is very suitable for homemade.
Small radio circuit diagram
As shown in the figure below is a system circuit diagram of a small station. The power supply is supplied from (; k2 socket input, after filtering with C16, C17, C18, C14, C15 filtered into FC2, the + 5V voltage regulator power supply is used to supply FC1, and 2 bits in the 6-digit switch (Figure 2) The M1, M2) of K1 is given to the microphone amplifying circuit. MIC1 converts the speech signal into an electrical signal, fed into the audio amplifier composed of V1, R6, R7, etc. via C3, and the amplified audio signal is adjusted by C5 to RP1. The volume, finally passed through the left channel signal input of IC1. MIC2, V2, RP2, C24, etc., to form a right channel audio amplification circuit, and sent to the right channel signal input of LC2. D0, D1, D2, D3 (Ie the 15 to 18 feet of IC1) The 4-bit switch of K1 is used to set the transmit frequency. The composite faster stereo carrier signal is output from the 11 foot of the LC1, coupled by C36, and feeds from V3, R21, L3, The high-frequency amplification circuit consisting of C37, the amplified signal is sent out by the C38 feed antenna Ant1. The external audio signal is input from the CK1 .LED1 is the power indicator. CK2 is the external power input socket, can be used with the empty core plug, plug The center is the positive pole.
Making and debugging the above figure is a circuit board for making a good small station, which can refer to the mounting diagram of the diagram in the welding device, and the specific installation process can be refer to the figure below. After the welding is completed, the system is powered by an 8 ~ 12V DC power adapter to start commissioning. Place the M1 and M2 of the DIP Switch K1 in "ON", so that the microphone works. The settings of the DO, D1, D2, and D3 in K1 can be referred to the pre-L2 of the following table to increase the pre-L2.
Serial number
DO
D1
2
D3
frequency
1
L
L
L
L
87.7
2
Hide
L
L
L
8917
3
L
Hide
L
L
88.1
4
Hide
Hide
L
L
88.3
5
L
L
Hide
L
88.5
6
Hide
L
Hide
L
B8.7
Seduce
L
Hide
Hide
L
88. 9
~
Hide
Hide
Hide
L
Stop
8
L
L
L
Hide
106.7
9
Hide
L
L
Hide
106.9
10
L
Hide
L
Hide
107.1
11
Hide
Hide
L
Hide
107.3
12
L
L
Hide
L
707.5
Mean
Hide
L
Hide
Hide
107.7
14
L
Hide
Hide
Hide
107 9
~
Hide
Hide
Hide
Hide
Stop
Take a radio to adjust its reception frequency to the frequency point of the small station, talk to the microphone, listen to the radio has no signal. If you are not received, you can properly stretch L2 usually can be resolved. Carefully adjust the L2, so that the signal is the most stable, the background noise is minimum. If an external audio signal, such as a computer, an MP3 player, etc., the M1, M2 should be placed in the "0FF" state, allowing the microphone to stop working. In inputting the audio signal from the CK1, you can hear the sound played from the audio device using the radio.
(d) IC1, D1, V4 are patch devices, and it is necessary to pay attention to the pin distribution of DL and V4 when welding. The end of D1 has a vertical line is an negative electrode
(e) Use a wire of about 1M as antenna, or a tie rod antenna can also be used.
(F) on the printed circuit board. J1J2 can be across excess devices
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