Radio direction finding and PJ-80 type direction finding machine circuit

The radio direction finding movement originated in the 1960s. It was introduced to China from Europe in 1960. It is similar to the well-known hide and seek game, but instead of looking for someone, it is looking for the source of the transmitted signal. Radio "Hide and Seek" is a combination of modern radio communication technology and traditional hide and seek games. The general process is: in the wilderness, hills, jungles or suburbs, parks and other natural environments, 3 to 10 signal sources (ie small transmitters) are hidden in advance ), Morse code signals for different calls are sent out regularly. Participants held a radio direction finder and measured the direction of the hidden radio station. They used a walking method to quickly and accurately find these signal sources one by one, so as to find the specified number of units within the specified time, and the less time is the winner. Usually, we compare the signal source cleverly hidden in advance to a cunning fox, so this sport is also called radio "fox hunting".
At present, there are three main types of radio direction finding activities in China: one is the short-distance 80-meter short-wave direction finding suitable for popularization and promotion in middle schools, youth science and technology centers (stations), juvenile palaces, and activity centers; the second is the 160-meter medium-wave direction finding The third is long-distance 80-meter short-wave band and 2-meter ultra-short wave band direction-finding in accordance with the rules of the international direction-finding competition and suitable for college and middle school students.
Participating in this activity, in addition to the knowledge and technology of radio direction finding, you can also learn the basic knowledge about the circuit, master the direction finding machine and other electronic production skills. Because it is not purely scientific and technological indoor production, nor a single run on a fixed venue, but fully embodies theory and practice, hands-on and brain, indoor and outdoor, physical and intellectual combination, to promote youth moral, intellectual, The comprehensive development of physical, beauty and labor is very beneficial to enrich the content of the second classroom of the school.
Model PJ-80 is a popular direct-release 80-meter band direction finder. It has a simple circuit, low cost, and is easy to install. It is very suitable for the use of radio direction finding and assembly by young people. The block diagram and circuit principle of the whole machine are shown in Figures 1 and 2. Show.
L1 is a magnetic rod antenna, A is a whip antenna, K1 is a single and bidirectional switch, used to determine the direction of the radio station, BG1 and peripheral circuits form a high-frequency amplifier, and the high-frequency Morse code signal received by the antenna is amplified and then coupled out by B1. . BG3, C14, C15, D2, C16, C17 and C18 form an adjustable deformable capacitor three-point oscillator. Adjusting W2 can change the reverse bias voltage of the varactor diode D2, thus changing the capacitance of the tube to change the oscillation frequency. Voltage regulator D3 is used to eliminate the unstable oscillation frequency caused by the drop in battery voltage. The oscillation signal is superimposed with the high-frequency signal output by B1, and then the diode D1 is mixed to generate a beat signal. The audio signal generated after detection and low-pass filtering is amplified by a low-frequency power amplifier circuit composed of BG2 and LM386, where D1 is mixed. And the dual role of detection. K2 is the power switch controlled by the headphone socket. When using stereo headphones, K3 is closed.
Commissioning 1. Inspection of working point: the voltage regulator D3 can take 3.5 ~ 4.4V. When W1 is placed at the maximum gain, the voltage across R3 is about 0.4 ~ 1V (Ic1 is about 0.4 ~ 1mV), and R9 is both ends. The voltage is about 1.5 to 3V, and the voltage across R12 is about 2 to 2.5V.
2. Frequency coverage debugging: W2 is placed in the center position, the high-frequency signal generator is set at 3.5 to 3.6MHz, and the frequency button of the high-frequency signal generator is turned, so that the direction-finding machine receives a signal of tone change, indicating that the machine is beat The oscillator is working. The high-frequency signal generator is set at 3.55MHz, and the B2 magnetic core is adjusted to hear the signal; rotate W2, you can hear the 3.5MHz and 3.6MHz equal-amplitude signals respectively output by the high-frequency signal generator, and the ends are slightly Surplus. If you can't hear it at the high end and there is a large margin at the low end, you can turn the B2 core slightly outward; otherwise the opposite is true.
3. If the listening frequency is too wide, increase the resistance of R14 appropriately, otherwise, reduce its resistance.
4. Adjustment of the antenna circuit: the high-frequency signal generator outputs a signal of 3.53MHz, and the position of the coil on C1 and the magnetic rod is adjusted to maximize the sound.
5. The adjustment of the high-amplifier circuit: the high-frequency signal generator outputs a signal of 3.57MHz and adjusts the B1 core to maximize the sound.

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USB 3.0 Interfaces Section

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USB3.0 is a USB specification, which was initiated by Intel and other companies. The maximum transmission bandwidth of USB3.0 is as high as 5.0gbps (500MB / s).
While maintaining compatibility with USB2.0, USB3.0 also provides enhancements: significantly increased bandwidth (up to 5Gbps full duplex); better power management; 
more power; faster device identification; and higher data processing efficiency.  
The reason why USB 3.0 has the performance of "speeding" is entirely due to the improvement of technology.
Compared with USB 2.0 interface, USB 3.0 adds more physical buses in parallel mode.
You can pick up a USB Cable and look at the interface.
On the basis of the original 4-wire structure (power supply, ground wire, 2 pieces of data), USB 3.0 adds 4 lines for receiving and transmitting signals.
So there are eight lines in the cable and on the interface.
It is the additional 4 (2 pairs) of lines that provide the bandwidth required for "superspeed USB" to achieve "over speed".
Obviously, two (1 pair) lines on USB 2.0 are not enough.
In addition, in the signal transmission method, the host control mode is still used, but the asynchronous transmission is changed.

USB 3.0 makes use of two-way data transmission mode instead of half duplex mode in USB 2.0 era. In short, data only needs to flow in one direction, which simplifies the time consumption caused by waiting.

In fact, USB 3.0 does not take any rarely heard of advanced technology, but theoretically increases the bandwidth by 10 times. As a result, it is more friendly and friendly. Once superspeed USB products come out, more people can easily accept and make better customized products.

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