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How a Satellite TV Antenna Works
by Gary Davis
 Practically
all broadcast systems use antennas to transmit and receive radio
signals. These antennas are based on single metal pole to which
the carrier signal is sent through a cable. First let’s
talk about how this most simple type of antenna works:
Pole Antenna
A Pole antenna basically consists of one metal pole that transmits
it signals around it as if it was the center of a sphere. In
all directions the transmitted signal has the same power. The
length of the antenna is determined by the frequency of the
transmitted signal.
Radio waves, like light waves, always travel at the same speed,
which is about 186.000 miles (300.000 km) per second. One wave
length is determined by the frequency of the signal by the following
formula:
Wavelength = speed of light / frequency
This results in higher frequencies having shorter wavelengths.
A pole antenna doesn’t have to have the length of a complete
antenna but can also have a length of about ½ , 1/8,
or 1/16 of the wave length. This is done mostly for practical
purposes (shorter antennas). Wave lengths for pole antennas
can go as high as 1 to 2 Giga Hertz. A cell phone for instance
works at frequencies of 950 Mega Hertz which is almost 1 Giga
Hertz.
Satellite TV or Parabolic Antenna
A satellite TV Antenna or parabolic antenna works on the same
principle. The frequencies used by satellite transmissions are
of much higher frequencies; 2 Giga Hertz or higher. Wavelengths
get so short at these frequencies that it is not possible anymore
to transmit using a pole antenna and transmit in all directions.
The power needed would be very high because high frequencies
are subject to much more resistance from the atmosphere.
Bundling all the transmitted power into a beam improves the
power transmitted in one direction by a huge factor. Depending
on the distance between the transmitter and the receiver the
amplification compared to a normal pole antenna can be as high
as 40 to 50 dB (which is as much as 10.000 to 100.000 times
amplification).
In reality the beam is not completely straight, but gets wider
over the distance. The angle is small, but in case of an antenna
on a satellite that transmits all over the USA the angle is
actually a little bigger so that the whole USA is covered.
The antenna at your roof or in your garden is pointed at the
satellite and receives the signal and does the same thing; it
bundles the radio waves into a point, thus amplifying the radio
signal with 40 to 50 dB. (see illustration below).
Amplification in the whole path is extremely big. The transmitting
antenna amplifies, the receiving antenna amplifies, the transmitter
it self amplifies, and the receiver itself also amplifies the
signal. A total amplification of over 120 dB (over 1.000.000.000.000
times) is necessary because the atmosphere and also the long
distance just decrease the signal power a lot.
By Gary Davis
Dish-Network-Satellite-TV.ws
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About The Author
Gary Davis is the owner of Dish Network Satellite TV, has several
years experience in the Satellite TV Industry and has written
numerous articles about satellite TV.
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