(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.