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How to solve the transmitter SWR is too high, What causes high SWR?

Published:2019/9/24 17:08:02 Visits:
  • What is standing wave ratio(SWR)?

    Standing wave ratio (SWR) is a numerical value used to indicate whether the antenna, feeder and transmitter match. If the standing wave ratio is equal to 1, it means that the radio waves transmitted by the transmitter to the antenna do not have any reflection and are all emitted, which is the best case. If the standing wave ratio is greater than 1, it means that part of the radio wave is reflected back and eventually becomes heat, which makes the feeder warm up. The reflected wave also generates a high voltage at the transmitter output, which may damage the transmitter. So the SWR of the transmitter should be controlled below 1.5.

  • The failure caused by too high standing wave ratio
  1. The transmitting power does not reach the rated power and the transmitter coverage is low
    Standing wave ratio (SWR) plays a role in blocking power transmission, so too high SWR will lead to low power transmission of the transmitter, thus reducing the coverage.
  2. The transmitter power is 0.
    When the standing wave ratio is high to a certain value, the transmitter stops working and enters the protection mode to prevent the power amplifier board from burning down.
  3. Transmitter temperature is too high
    The higher the standing wave ratio, the higher the heat. Finally, the temperature of the transmitter becomes higher.
  4. The power amplifier is burnt down
    When the standing wave ratio becomes high, the radio waves will not emit at all, and these waves will stay in the power amplifier tube and generate huge heat, resulting in the power amplifier tube burned.
  5. The transmitter working is unstable
    High standing wave ratio will lead to higher transmitter temperature. High temperature and standing wave ratio can easily cause the transmitter to stop working and enter protection mode. And the transmitter has been working in the high-temperature environment will shorten the life of the transmitter.

  • Causes that the standing wave ratio is too high
  1. The transmitting frequency does not match the antenna frequency
    The antenna is at design time to determine its frequency range, or it needs to be replaced frequency by manually extending the length of the oscillator. So when the transmitting frequency is not in the antenna frequency range, the SWR of the transmitter will be too high.
  2. The installation environment of the antenna is not up to standard
    The installation height of the antenna needs to be 5 meters above the ground. No obstacles can be found within 10 meters around the antenna. Otherwise, Airwaves emitted by the transmitter will be reflected back by these obstacles, which will cause SWR to be Increase.
  3. The Feed tube is not installed correctly
    The presence of Impurity in the feeder, the length of the feeder is too long or roll up and install up will cause interference, which will eventually lead to a high standing wave ratio.
  4. The antenna quality is not up to standard
    If the quality of some antennas is not good, then its standing wave ratio will be higher, and the standing wave ratio of each frequency point of the antenna is different. For the same antenna, the standing wave ratio of some frequency points will be higher and some frequency points will be lower.
  5. Feeder tube quality does not meet the standard
    Poor feeder tube quality will result in lower transmission performance and higher SWR.
  6. The antenna or feed tube is damp or there is water
    If there is water in the antenna or feeder, it will affect its electrical performance, resulting in higher standing wave ratio.
  7. Poor contact between connectors
    If the connectors between the joints are poor, the radio wave will not be fully emitted, and finally, the standing wave ratio will be too high. If the transmitter power exceeds 500W, There may even be a spark between the connectors. It may burn the transmitter or cause a fire.
  8. Transmitter SWR detection error
    If the VSWR detection function of the transmitter has been damaged, or the whole power amplifier board has been damaged. Then his standing wave ratio will not show the value accurately, there will be too high.

  • Solving the method of standing wave ratio is too high
  1. Check whether the transmission frequency is within the range of antenna usage frequency. If the antenna needs to adjust its length to modify its usage frequency. Please adjust the length of the antenna to a suitable range.
  2. Check if there are obstacles around the antenna. If there are obstacles, clear them or transfer the antenna.
  3. Check if the feed tube is roll up and install or if there are foreign objects in it. If so, please straighten the feeder as far as possible and clean up the foreign body.
  4. If there are other antennas or feed tubes, please replace the test to see if it is an antenna or feed tube quality problem.
  5. Check for moisture in the antenna and feed tube. If there is, please dry and use again and check where the water comes in. Wrap it with a waterproof tape.
  6. Check the interface between the transmitter and the feed tube, feed tube and antenna for tightening. If not, please tighten the it. (If the power divider is used, the interface between the power splitter and the feed tube should also be checked)
  7. If it is confirmed that the power amplifier board or the standing wave ratio detection chip is damaged, please replace the power amplifier board or the standing wave ratio detection chip.


Antenna installation instructional video 3

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