Why the shape of tv antenna is so ?

Answer 1

shape r for some reasons if u can understand then u read these

Frequency versus length
Dipoles that are much smaller than the wavelength of the signal are called Hertzian, short, or infinitesimal dipoles. These have a very low radiation resistance and a high reactance, making them inefficient, but they are often the only available antennas at very long wavelengths. Dipoles whose length is half the wavelength of the signal are called half-wave dipoles, and are more efficient. In general radio engineering, the term dipole usually means a half-wave dipole (center-fed).

A half-wave dipole is cut to length according to the formula l = 468 / f, where l is the length in feet and f is the center frequency in MHz [1]. The metric formula is l = 142.65 / f, where l is the length in meters. The length of the dipole antenna is about 95% of half a wavelength at the speed of light in free space. This is because the velocity of propagation of electromagnetic waves in wire is slower than that in free space

Set-top TV antenna
The most common dipole antenna is the "rabbit ears" type used with televisions. While theoretically the dipole elements should be along the same line, "rabbit ears" are adjustable in length and angle. Larger dipoles are sometimes hung in a V shape with the center near the radio equipment on the ground or the ends on the ground with the center supported. Shorter dipoles can be hung vertically.


Folded dipole
Another common place one can see dipoles is as antennas for the FM band - these are folded dipoles. The tips of the antenna are folded back until they almost meet at the feedpoint, such that the antenna comprises one entire wavelength. The main advantage of this arrangement is an improved bandwidth over a standard half-wave dipole.


Shortwave antenna
Dipoles for longer wavelengths are made from solid or stranded wire. Portable dipole antennas are made from wire that can be rolled up when not in use. Ropes with weights on the ends can be thrown over supports such as tree branches and then used to hoist up the antenna. The center and the connecting cable can be hoisted up with the ends on the ground or the ends hoisted up between two supports in a V shape. While permanent antennas can be trimmed to the proper length, it is helpful if portable antennas are adjustable to allow for local conditions when moved. One easy way is to fold the ends of the elements to form loops and use adjustable clamps. The loops can then be used as attachment points.

It is important to fit a good insulator at the ends of the dipole, as failure to do so can lead to a flashover if the dipole is used with a transmitter. One cheap insulator is the plastic carrier that holds a pack of beer cans together. This beer can insulator is an example of how a household object can be used in place of an expensive object sold for use as an item of radio equipment. Other objects that can be used as insulators include buttons from old clothing.

Answer 2

depends on the TV antennae. if you are talking about the type of antennae that has the different sized spokes atop a pole..well the spokes are different sizes to better interact with different types of broadcast waves at different frequencies. picture a dropped stone in water...the concentric ripples are representative of the waves of energy that TV energy is. now look at the distance between the ripples...that's the frequency or rate the waves go out. if you wanted to catch the most waves or ripples..you get a stick long enough to intercept the ripples from ripple to ripple. since all waves aren't on the same frequency length..you put a bunch of different sized sticks out to catch the most waves.

hope that helps