When the level signal is insufficient, the image will appear snowflake point. At this time, the trunk amplifier must be used to raise the level.
When the level signal is insufficient, the image will appear snowflake point. At this time, the trunk amplifier must be used to raise the level.
The function of the amplifier is to increase the level of each transmitter in the cable by 25-30DB at the same time. Therefore, the position of the trunk amplifier will affect the image.
Putting it too far forward will raise the level of the nearby transmitter too high, thus affecting the far-end transmitter (all the transmitters in the cable). The target=_blank> machine level value is greater than the minimum value. 20DB, prone to adjacent channel interference, horizontal stripes, twill and other interference); placed in the far post, the transmitter in the distance "target=_blank> machine level value is too low (
Therefore, at this time, it is necessary to use a field strength meter to detect the signal strength of all the transmitters in the cable. At a certain point (generally the contact between the cables or the position before the access to the distributor), after detecting the level of all the transmitters, if there is a minimum level close to 75DB, this is Standard, all transmitter power "target=_blank> machine level is reduced to about 75DB (this step, called level equalization), and then connected to the trunk amplifier.
Note 1, the transmitter power that is generally close to the position of the trunk amplifier "target=_blank> machine level value is difficult to drop to 75DB, because the level adjustment of the transmitter itself can only drop 20DB, and the output level of all transmitters is above 110 Therefore, with the level adjustment of the transmitter, it can only be reduced to about 90. At this time, we usually use an attenuator or a splitter (the difference between branch and distribution is mentioned in other articles, please refer to) To force a drop level to achieve level equalization.
Note 2, if the position of the trunk amplifier, the trunk line should be connected to the trunk amplifier first, and all the transmitters in the cable are powered up to "target=_blank> level, then connected to the distributor. As mentioned above, join All the transmitters of the amplifier have a "target=_blank> machine level value of 75DB, and after amplification, the 30DB is increased to 105DB, and the other transmitters connected to the distributor are also close to 110DB, so that the newly added The "target=_blank> machine level value of the transmitter and the transmitter on the main line can also be equalized.
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