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Home > News

How do analog TV transmitters use vertically polarized transmit antennas

Published:2019/9/24 17:12:34 Visits:

Testing purposes

  • Most TV transmitters in the market use horizontally polarized antennas, but horizontally polarized antennas are very expensive to transport.

  • If a vertically polarized antenna is used as the transmitting antenna, the cost of the entire product will become very low.

  • So we need to test the feasibility of this program.

test environment

  • Transmitter power: 10W

  • Transmitting antenna gain: 5dB

  • Antenna installation height: 80 meters

  • Receive antenna gain: 13dB

Transmitter end test environment

Receiver end test environment

  • Antenna vertical installation
    image

  • Antenna horizontal installation
    image

First test point -1KM

  • Test location
    image

  • Receive picture - antenna vertical installation
    image

  • Receive picture - antenna horizontal installation
    image

Second test point-2.5KM

  • Test location
    image

  • Receive picture - antenna vertical installation
    image

  • Receive picture - antenna horizontal installation
    image

Third test point-5KM

  • Test location
    image

  • Receive picture - antenna vertical installation
    image

  • Receive picture - antenna horizontal installation
    image

Test conclusion

  • The transmitting antenna is vertically polarized, and the receiving antenna must be installed vertically.
    If the antenna is installed horizontally, the coverage will be only One-fifth of the vertical installation.

  • In this test, the antenna is installed vertically, and the transmitter is 5KM away from the receiver.
    can still see the image, but there are more snowflakes, and already can’t watch the program properly.
    But there is 514 Mhz GDTV TV signal interference in the test point, and there is also a barrier between transmitter and receiver.

  • The differences between this test and the actual use are:

    1. The antenna is installed at a height of 80 meters, while the feeder is only 15 meters. In actual, there is no such high tower, and a longer feeder will be used, and the line loss will be higher than this test.
    2. Because the test antenna is installed in a balcony, half of it is surrounded by walls. Therefore, the standing wave ratio will be higher than the actual use, resulting in the radiation effect is worse than the actual use.
    3. This product was originally designed to solve the problem of fewer or no TV stations in small villages. Therefore, the actual environment used will be cleaner than this test, and there will not be so much interference.
  • So I think that in practical use, 10W TV transmitter uses 5dB vertical polarized antenna at 511 Mhz frequency while receiving antenna is installed vertically. There is no problem covering 3KM.

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