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VGA twisted pair transmitter: In order to solve the problems of image ghosting and color distortion when transmitting VGA signals over a long distance, it is designed for network flat panel display and large screen curtain wall display advertising engineering, industrial automation control, medical equipment, Security monitoring, multimedia teaching and other display system engineering requirements for high-quality VGA video signal transmission over long distances. Professionally designed signal transmission system that integrates VGA signal conversion, distribution, driving, receiving and restoring functions.

VGA twisted pair transmitter

It can balance the transmission of VGA signals through unshielded five types of network cables to enhance the suppression of common mode noise and interference signals, while greatly saving the cost of wire and simplifying the engineering wiring. The patented technology is used to encode H and V signals onto RGB signals and send them after processing. Only three pairs of CAT-5 cables are used to complete the balanced encoding and decoding of RGBHV signals of VGA, SVGA, SXGA, XGA, and SXGA. Long-distance high-frequency compensation and emphasis processing, bandwidth up to 350MHz. Make the transmission distance of XGA (up to 1600 * 900 / 60Hz) reach 300 meters to meet the needs of large-scale engineering projectors, displays, TFT-LCD TV, and PDP signal transmission. Because the entire transmission system uses the patented technology of balanced transmission with weighted zero value splitting, the twisted pair cable will not cause external EMI interference when transmitting signals. You can adjust the distance of the transmission distance by setting the DIP switch.

VGA signal transmission is a recent hot spot for video signal transmission. Various transmission methods have attracted the attention of many engineering companies. Various publicity has also blurred the normal judgment of engineering companies. As a manufacturer of twisted pair transmission, VGA A brief discussion of the development and principle of transmission, hope to clarify the possible misjudgment of everyone!

The VGA signal contains five types of R / G / B / H / V, which are the three primary colors and the horizontal and vertical synchronization signals. Although VGA cable contains 15 wires, there are only 5 wires in the VGA cable that actually transmit the image signal, so to see if the VGA cable is good or not, first look at the core quality of the five wires used to transmit RGBHV.

Although the VGA wire core is very small and the attenuation is relatively large, the VGA wire will basically have no problem when transmitting over a short distance. In the early days, in order to solve the problem of long transmission distance, the core diameter was generally increased, and the copper core was made very thick. However, after a long transmission distance, the problem of crosstalk between the five signals in the VGA line becomes serious. At the same time, the thick VGA wire is extremely difficult to route in a more complicated environment. The VGA line is easily broken when turning, and there are many other problems. (Such as: external interference, bad welding points, etc.).

In order to solve the problem of VGA video transmission in the project, the development of VGA video transmission according to time sequence is: (VGA cable + VGA amplifier) (RGB cable + RGB long-line driver) (twisted pair + twisted pair transmission equipment)

A) VGA signal amplifier

It uses a simple amplification principle, either to amplify the signal at the transmitting end or to amplify the signal at the receiving end. The amplification method at the receiving end is discarded as soon as it amplifies the interference in the transmission, including crosstalk between internal signals. The device using the transmitting end amplification can transmit the computer's VGA video signal over tens of meters after using a special VGA video cable as the transmission medium. But then people made the VGA wire core thicker and thicker, and the disadvantages of not changing the principle of VGA transmission technology became more and more obvious:

First, the long-distance VGA cable is thick and hard, and it is not easy to find. It needs to be customized at the factory. It is prone to internal fracture due to sharp turns, and the wiring is extremely inconvenient.

Second, VGA heads are also prone to various problems (such as standing wave interference, false soldering, etc.) when soldering.

Third, it cannot resist interference and cannot eliminate crosstalk. The VGA cable itself determines that it has long internal transmission crosstalk and common mode interference. As the distance increases, some interference that is not very strong also becomes strong in the long-distance wire, which leads to success in some test environments, but there is no way to apply the actual project, resulting in huge rework or unacceptable acceptance. loss. Therefore, this method should not be used over a distance of 30 meters.

B) RGB transmission technology:

According to the principle that the VGA signal is divided into five types of RGBHV signals, the VGA cable is split and transmitted using five coaxial cables. This transmission method is called RGB transmission. This method effectively solves the problem of attenuation (the core of the RGB cable is much thicker than the single core of the VGA cable). At the same time, the shielding layer of the coaxial cable can also suppress the crosstalk to a certain extent. The technical principles have not changed fundamentally, and the crosstalk problem has not been solved! In addition, after the RGB transmission distance reaches a certain distance, due to the complex construction site environment, the five RGB cables that transmit RGBHV signals have different lengths and different arrival times during wiring, resulting in the RGB three primary colors and the line-field signals not arriving simultaneously. The three colors appear on the screen cannot be superimposed or even displayed. This is the problem of unsynchronization that easily occurs in RGB transmission, and it is difficult to get a cheap solution to this problem.

C) VGA twisted pair transmission technology

In order to solve these transmission problems, a VGA video transmission technology using a common network cable (twisted pair) as the transmission medium has quickly become a hotspot of VGA video transmission technology.

This transmission method uses one transmitter and one receiver. The transmitter re-encodes the VGA video signal and transmits it on the network cable as a differential signal. It is decoded and restored to the VGA video signal by the remote receiver. The video differential technology used in the network cable transmission. When each pair of twisted pair cables transmits a signal, they simultaneously send out signals with the same waveform and opposite polarities. In this way, the signals emitted by a pair of twisted pair wires can cancel each other to zero. It solves the problem of crosstalk inside the VGA signal.

There are only 4 pairs of twisted pairs in the network cable. What should I do when using the network cable to transmit five types of VGA signals? In the early days, we divided the RGB in the VGA signal into 3 pairs of twisted pairs, and the remaining pair transmitted HV signals.

The length of each twisted pair in the network cable is also different. Isn't there a problem of out-of-sync? Solution: Line compensation! The difference from RGB cable transmission is that there is an international standard for the difference in the length of each twisted pair in the network cable. We can know the approximate difference in the line length of each twisted pair according to this standard, and perform line compensation based on this length. VGA signal can't be solved with RGB method. The problem is also solved here!

A ) Single transmission

The remote video and audio conference signal is transmitted to the terminal through the network, and then the signal is transmitted to the scene with high fidelity using a VGA twisted pair transmitter. This solution has simple engineering wiring, high stability, and excellent cost performance, and is suitable for large venues where multiple people watch the same screen. At the same time, it can be equipped with a professional standard rack, which is very convenient to maintain. As shown on the right:

B) Multiplexing

Multi-channel video conference is suitable for large conferences such as enterprises and administration. In order to better understand the progress and content of the conference, everyone participating in the conference needs a display device to ensure the conference is efficient and intuitive. This system is equipped with multiple 16-channel VGA transmitters and placed in the computer room for easy management. Each back-end display device is equipped with a single VGA receiver, which can extend the conference video and audio signals by 300 meters with high fidelity and no delay. . As shown below:

B) Composite transmission

Earlier, when we discussed several VGA transmission methods, we mentioned that ordinary network cables can be used to transmit video and mouse and keyboard signals. This system mode is very suitable for point-to-point, multi-person composite video conferences. The advantage is that it can share visual documents such as WORD and PPT on the same host with almost no delay. It is like sitting in the same office, which greatly saves time and space constraints and allows participants to be immersed. As shown below:

VGA twisted pair cables often encounter image problems during use, such as insufficient clarity, smearing, blurring, and color cast. Below we give specific solutions to common problems. Generally speaking, we will get satisfactory results after the following processing.

1. The image is tinted but more flickering

Cause: The adjustment switch of the extender is not adjusted normally.

Solution: Use the provided small screwdriver to slowly adjust the adjustment knob on the far end of the extender to a satisfactory image state.

2. The image font has tailing

There are several common causes of failure; 1. The crystal head is not pressed properly and the contact resistance is large 2. The remote adjustment switch is not adjusted properly 3. The quality of the network cable is too poor or the distance of the network cable exceeds the use distance and the distance is too long and the quality of the network cable is average

Solution: Adjust the knob on the far end, repress the crystal head, use a good quality crystal head to ensure good contact. Use a good brand network cable (super Category 5 cable is preferred), and the transmission distance is longer, please use our recommended brand cable

3.The screen is severely color cast, all red, green, and blue, and the distance is short and the tail is long, and the adjustment switch cannot solve it.

Cause of failure: The VGA interface part of the VGA extender has a problem of poor contact, a problem of poor contact of the crystal head, and the problem of incorrect use of a shielded network cable and a crystal head.

Solution: Check the VGA interface or replace the VGA cable, shake the crystal head, check for poor contact and test whether it is all-pass, and press or redo the crystal head. The short tail length is generally the shielded crystal head and the network cable Grounding problems, solutions, grounding, and using shielded crystal heads

4.No image is displayed at the far end, and the indicator light is off.

Cause: Generally speaking, the VGA interface is not connected properly and the network cable and crystal head are the problem.

Solution: Check the VGA interface and the cable part, make sure that it is smooth and in good contact, and check whether the network cable and the crystal head are well connected and in good contact.

5. The image has diagonal lines and stripes

Failure reason: Generally there is strong electromagnetic interference nearby.

Solution: wiring disturbs the source of interference, or use shielded network cable and crystal head