Electric field polarization in different stations

[Gizew]

evelam00@gmail.com how is the electric field from AM broadcast stations polarized? from TV stations? from FM broad cast stations? is there any cionnection between this polarization and orientation of receiving antenna?

 

[Pumblechook]

AM stations are vertical. The aerials are usually mast radiators or T aerials. This gives low angle radiation. A hozirontal dipole would fire too much radiation at a steep angle due to ground reflections.

At VHF and UHF there is no deep technical reason why either should be used. The choice is more of convenience. It is said Horizontal can be a bit better over hilly areas and where there are a lot of trees but it may be marginal or just a theory.

TV is either. As the wavelength is so much shorter you can get transmitting aerials many wavelengths above ground and ground reflections have little effect. A mixture of hor and vert is used to reduced interference.

In Britain FM was horizontal because it was intended for home use and roof yagi aerials are easier to mount horizontally and look neater. These days slant or circular (both sometimes called 'mixed') is used to accommodate both home listeners and people in cars. It is also better for portable sets with telescopic aerials. Circular allows reception with the receiving aerial at any angle.


A vert transmitting aerial requires a vertical receiving one. Circular polarisation requires both ends to be phased in order for the electric vector to rotate in same direction but broadcasting receiving aerials tend to simple hor or vert or at at any angle.

 

[oswaler]

The electric field from AM broadcast stations is polarized in a vertical orientation, meaning the electric field oscillates up and down. This is because AM radio waves are transmitted using vertical antennas.

On the other hand, the electric field from TV stations is polarized in a horizontal orientation, as TV signals are transmitted using horizontal antennas.

FM broadcast stations use both vertical and horizontal antennas, therefore the electric field can be polarized in either orientation.

The polarization of the electric field is closely related to the orientation of the receiving antenna. For optimal reception, the receiving antenna should be aligned with the polarization of the electric field. This is because the receiving antenna will be most sensitive to an electric field that is oscillating in the same direction as its elements.

Furthermore, the orientation of the receiving antenna can also affect the strength of the received signal. If the receiving antenna is not aligned with the polarization of the electric field, it may not capture the full strength of the signal, resulting in a weaker reception.

In summary, the polarization of the electric field from different broadcast stations is dependent on the type of antenna used for transmission. The orientation of the receiving antenna plays a crucial role in the reception of these signals. It is important for receiving antennas to be aligned with the polarization of the electric field for optimal signal strength and clarity.