造成視頻信號干擾的原因

详情描述：

視頻信號干擾主要表現在雪花點和50Hz橫紋滾動。
造成雪花點干擾主要是因為傳輸線上信號衰減以及耦合了高頻干擾所致，這種干擾比較容易消除。只要將信號的信噪比提高，或者改變視頻電纜的路徑避開高頻干擾源就基本解決。
至於50Hz橫紋滾動及進一步加入的高頻干擾會比較難解決。其解決方法：
1.採用帶有雙層屏蔽的視頻電纜。
2.想辦法使各處的「地」電位與「電網地」的電位差完全相同，例如：通過加大攝像供電線纜的線徑，儘可能降低地迴路的電阻。
3.採用切斷地環流迴路的方法，可減少50Hz的干擾，但不能完全消除。
因此，在工程設施和施工時，應全面考慮攝像機的供電電源線屏蔽;若到了系統調試時發現干擾，可採用調製和解調的方法將噪聲濾除。
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Causes of video signal interference
Video signal interference is mainly manifested in snowflake points and 50Hz 
horizontal stripes.
The cause of snowflake point interference is mainly caused by signal 
attenuation on the transmission line and coupling of high frequency 
interference, which is easier to eliminate. As long as the signal-to-noise ratio 
of the signal is increased, or the path of the video cable is changed to avoid 
the high-frequency interference source, the solution is basically solved.
As for 50Hz horizontal scrolling and further high frequency interference will 
be more difficult to solve. The solution is:
1. Use a video cable with double shield.
2. Find ways to make the potential difference between the “ground” potential 
and the “grid ground” everywhere. For example, by increasing the wire diameter 
of the camera power supply cable, the resistance of the ground circuit is 
reduced as much as possible.
3. The method of cutting off the ground loop circuit can reduce the 
interference of 50Hz, but it cannot be completely eliminated.
Therefore, in the engineering facilities and construction, the power supply 
line shielding of the camera should be fully considered; if interference is 
found during system debugging, the noise can be filtered by modulation and 
demodulation.
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