Author: Zhang Mingzhi
The author has a idle accessible V-type built-in information card, I want to use the high frequency head on the card, after receiving the relevant information, remove the high frequency head and increase the peripheral component, successfully produced a good performance. Channel FM receiver, satisfactory use effect. The high-frequency headed medium from the card can output a monologically sound and video, which reduces the debugging point during the production process, simplifies the circuit, as long as the component welding is correct, it can make success and achieve good performance. The production method is now introduced as follows for the vast enthusiasts.
1. The original high frequency head is integrated with the FC interface integrated high frequency head, so that it is separated from the PC control to manual control, and it is necessary to make some small changes to the high frequency head. Carefully open the high frequency header mask enclosure can see three integrated circuits, their name, function, and modified instructions see Table 1. Be careful when the integrated circuit is dense. The high frequency head pin definition after the change is shown in Table 2, and the frequency band selection principle is shown in Table 3, and the entire circuit schematic is shown in the drawings.
Be
Function
Change description
TSA5523M
1.4GHz Antenna I2C Bus Controller As a PC Communication Interface
5, 6, 7, and 7 (17) The foot is the frequency band selection control. Should provoked
TDA5736M
High placement, oscillation, mixing and VHF / VHF oscillation controller
(12) Poot control receiving frequency band, pick up the lead to lead the high frequency head 6 foot
TDA9800
Medium discharge circuit
No need to change
Be
Be
High frequency headrest
After the change is functional
1
Tuning voltage input (0 ~ 33V)
2
Tuning power supply (+ 5V)
3
12C bus serial clock (unused)
4
I2C bus serial data (unused)
5
I2C bus address selection (unused)
Six
Selection of frequency bands (provoke TDA5736M (12) feet, lead to this with wire)
Seize
Double channel control (unused)
In
Composite video output
Bamboo
Medium discharge circuit power supply (+ 5V)
Bamboo
Audio output
Be
Housing ground
Be
table 3
(6) foot voltage
Accepted frequency band
Receive frequency range
0V
VHF1
49-170MHz
2V
VHF2
160-470MHz
5V
UHF
460-865MHz
2. The tuning potentiometer uses a dedicated tunator of a plurality of l00k, if it is difficult to purchase in the market, the pre-selected plates of old-fashioned TVs can be used. The author used for a pre-selected plate selected by the 12-bit self-band, and its potentiometer rotates through the gear, and has a high tuning accuracy, and it can achieve a better tuning effect. For convenience, in addition to a main tuning, the remaining 11 bits can be used to store a station; although the number of mechanical stations is less, it is better than not good.
3. In order to be intuitive, the receiving frequency is probably known, and the full bias current is 100 μA, and the voltage dividing voltage of the tuning voltage is indicated by the potentiometer.
4. The entire circuit can be installed on a general-purpose experimental board. In order to achieve higher performance, it is necessary to add the power part to the mask. The shield can be welded by a thin copper sheet, and the tuning voltage input line is preferably monitored wire.
There is no special requirements for the remaining components.
After the production, the receiver can receive a frequency modulation signal in the range of 49 MHz to 865 MHz, which can be used as a frequency indicator under conditions of high receiving frequency. The author has a wireless microphone that receives signals with ordinary FM radio, and the FM receiver introduced herein can be convenient and easily and quickly adjusts the transmit frequency of the wireless microphone to the frequency range received by the normal FM radio.
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