(Upbeat techno music) Satellites have revolutionized
the way that we humans live. In this video, we are going to explore how satellite television works and also the big money flows associated with this broadcasting business. Towards the end of the video, we will also explain
the interesting reason why there is no buffering
of your TV broadcast in the way that internet
videos are buffered. To understand satellite
TV broadcasting properly, we first need to have some basic knowledge about the parts of a satellite and how a satellite moves. As you can see, the Earth revolves around the
Sun in an elliptical orbit, and the Earth also turns on it's own axis. You can see that this axis of rotation is not perpendicular to the
elliptical orbit surface but slightly inclined, as shown. For satellite TV to work, the satellite should not
move relative to your house. This means that the
satellite should rotate at the same speed as that of the earth. Which means, it will take 24
hours to complete one cycle. Let's work out the force
balance equation of the gravitational and
centrifugal forces at this point using this speed information. You can see that the orbital
radius required to achieve the no relative motion
condition, for the satellite, is exactly 42,164 kilometers. This orbit is known as
a geostationary orbit. All satellites used for
satellite TV purposes should be parked in this orbit. And this visual shows how
crowded the geostationary belt has become nowadays. Now, let's find out a few things
about the satellite itself. The energy required for a
satellite mostly comes from it's solar panels. However, if the satellite
is not facing the sun, a battery pack helps to
continue it's operations. It is interesting to
note that satellites have small engines called thrusters. The gravitational field
experienced by a satellite is not uniform due to irregularities
on the Earth's surface and the presence of the Moon and the Sun. The thruster produces a very
minute amount of force to keep the orientation and position
of the satellite correct. The most important part of a
satellite for communication purposes is the transponder. The transponder's receive
signals from the base station at one frequency, amplify
the power of the signal, remove any noise and
transmit it back to earth at a different frequency. The uplink frequency is always higher than the downlink frequency. You can see antennas of
different frequency bands. For D2H, the Ku Band
frequency is generally used. These Ku Band Signals have good power, which allows a smaller
size receiver antenna. In the past, C Band signals, which have lower energy, were used for television communications and that's why huge antennas were used in those earlier days. However, Ku Band signal's
are affected by rain. So, scientist's have had
to overcome this issue with improvements in satellite technology. Now that we have some basic information, let's see how hundreds of TV
channels reach to your home via the satellite TV technology. Consider the case of this TV channel, CNN. They have a video production facility and keep on producing content
for mass viewing, 24/7. We call them a program source. This channel needs to be
available at the same time on many satellite TV broadcasters networks. We call them DBS providers. To achieve this, CNN just
beams their signal to their rented transponder in
it's geostationary orbit. It should be noted that before
sending the video signals, the program source inserts
advertisements as suitable points and this is the first source
of income for the channel. Now the CNN signal is commonly
available at one point, and any DBS provider can access the signal once they have made a business agreement with the program source. Similarly, the DBS provider
collects signals from many such channels or program sources. At their broadcast center, they club all these content together and do video formatting
like MPEG compression, standardization of bit rate, and encryption of the signal. After that, the DBS provider
beams the signal to their rented transponder in a satellite. A DBS provider rents many
transponders to handle the huge amount of data
they have to transmit. This way around 300-400
channels will be available on a single DBS provider satellite. Now the last phase in signal transmission; the transmission of the
signals to the end user. Here, the end user has to
angle their dish antenna towards the DBS providers satellite. You might have seen that
for different DBS providers, there are different angles for the dishes. Even if the dishes are
all in the same location. This is because the different
providers might be using different satellites for
transmitting their signals. The signals received by your dish are encrypted to prevent piracy, and only a dedicated
card in the set top box will be able to decrypt it back. Do you know that the live
events you are watching on your satellite television are actually delayed by a few seconds? The signal leaving the broadcast center has to travel a huge
distance via two satellites before it reaches you. Even though the signal
travels at the speed of light, such a huge distance will cause a delay of around 0.5 seconds. Moreover, a live broadcaster may also add a specific profanity delay
on top of the normal delay. Now for the interesting comparison between internet videos and satellite TV. Both of the television
and internet technologies transmit data in a digital
format, as zeros and ones. Why is there no buffering on your TV, in the way that you see it on
YouTube or Facebook videos? On satellite television,
the broadcaster offers only 300 to 400 channels or video streams and the user has to select just one from this small collection. However, on the internet,
the demands of each user are very different. There are millions of videos
on the internet to choose from. This means that the volume
of traffic handled by TV broadcasters is no where close to the level of internet traffic, and it is this huge level
of traffic on the internet which made may sometimes
cause traffic congestion and buffering. This video explains how
satellites play a role in television broadcasting. To understand how satellites
help your GPS to work, please check our next
video in this series. Thank you.
