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| Antennas radiate the electromagnetic waves straight ahead. If the antennas mounted to the tower at right angle to earth, the electromagnetic waves travel parallel to ground. |
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| Normally almost every transmittig site is located higher than the target area. So to transmit the maximum energy from the transmitting system to the target area, the radiated beam needs to be directed there, otherwise few / some / much of the energy from the transmitting system goes to unnecessary areas. |
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| This is one of the the answers of a general question in terrestrial broadcasting, “I have the same system like some others, but I can not receive the same signal” |
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| Directing the signal beam to the target area is called “tilting” and it includes some other parameters. |
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| There are two tilting techniques: Mechanical and electrical tilt |
| Mechanical Tilt: This is done by tilting the antenna physically to the target area. But for the bigger and compex antenna systems, the physical implementation of tilting antennas gets too difficult on high towers and also the beam loses its uniform pattern. |
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| Electrical Tilt: This is done by arranging the phases (lengths) of the branch feeder cables. This needs an engineering study and application with high-tech equipments but this is the best way to optimize the broadcasting signal (vertical pattern). |
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| Even though a mechanical tilt was done , the engineering study for electrical tilt should be accomplished to optimize the beam (vertical pattern) because if the phases of the branch feeder cables are wrong then the system might be broadcasting to sky (Vertical Radiation-B ) or to somewhere unncessary (Vertical Radiation-A) |