Its so wonderful to see different nations of the world coming together to compete with each other in oneness and unity, though I am not much of a football fan, but I am certainly a fan of the world cup, seeing that it brings the world together, irrespective of country, race, color or Religion.
Of course not every one would have the time or resources needed to travel to Russia to witness this historical season of the world, that’s exactly where theLive broadcast technology comes in, from the comfort of our sofa with a chilled drink and a snack we can sit back and watch the world compete with each other in a farther distance. But before you turn on that TV to watch the next match.
Lets understand how the technology works.
Let’s take our cue from football matches or event live-broadcast on Television stations, I know you might ask, I watch matches through my Local Television stations without the need of a satellite dish or something,
how come?
The fact is that even if there was a Local Television station in Russia, it would still be impossible to broadcast to Nigeria without Satellites, so what they do is to pick the events via satellite and rebroadcast locally to Nigeria.
Okay let’s come more local. Have you ever seen certain matches on say AIT and you get confused on whether you are watching AIT or NTA as you see both logos embed on the TV screen? You see local stations picking events via satellites is very expensive and at times, local TV stations consider it more economical to collaborate with each other to show this matches.
LIVE-BROADCAST TECH
The invention of the television is a very tremendous innovation. Its uniqueness is not only in its ability to present a visual representation of past events, but in its ability to present information to the world at the speed of light.
Imagine our intention of watching a football match days after it has been played and result has been announced, the only set of people that would catch in on the suspense and the tension are the ones who paid for both flight and ticket to and in the location in which the match is being played. Well the technology which is somewhat a package that comes with the television technology is the live-broadcast technology.
Just a side note, but the difference between livestream and live-broadcast is that; live-streaming is transmitting real-time signals over the internet while live-broadcast is transmitting real time signals over Television networks and stations.
THE TELEVISION SYSTEM
The Television system was a product of many contributions from many individuals from the closing of the 19th century up to the beginning of the 20th century. At start, it was impossible to transmit moving images (videos), because of the sensitivity of the scanner wasn’t high enough, best that could be transmitted was sound and pictures over cables, wireless transmission was impossible due to a deficiency in the knowledge of electromagnetism.
A quantum leap was achieved by the Scottish inventor John Logie Baird in the 1920’s where moving images (video) was made a reality through the Nipkow disk.
That was just a brief background to the history of television now let's get do some business.
To simplify things up, television simply refers to “radio with pictures” that’s the idea, so then like your normal radio transmitting sounds, fast varying picture bit rate is also transmitted over the same radio waves,
What are Radio waves any way; Radio waves are electromagnetic waves (due to small wave lengths they are invisible patterns of simultaneously travelling electric and magnetic field over a any medium), travelling at lights speed, with the longest wavelengths (from say 1 mm – 100km) and lowest frequencies (3kHz-300GHz). Basically the system
The television system basically comprise of 3 stages;
The TV camera
The TV transmitter
The TV receivers
The fact that you have access to watch that match from the comfort of your home simply means that there are people there taking the responsibility of taking the video feed of every detail of that match.
Basically, videos are fast moving pictures, and they move so fast as to create a a video impression in your brain. (Lots of pictures in this case you know).
Let's do a quick experiment with your phone, well the kind of phone matters;
Open the camera and press down the capture button for few seconds. The consequent view it would give you, is like that which your normal video would.
The TV camera in that pitch is therefore used by certain television companies to take live feed of the match.
HOW EXACTLY DO TV CAMERAS WORK: Cameras work like the human eye. The technology behind the human sight could seem somewhat magical, but in the real sense of things, our sense of vision works when the things we see reflects light Into our eyes; the light reflected forms pixel patterns that later results to an image, the brain thereby acts as an interpreter of this patterns.
Well the working of the camera is therefore not farfetched; the camera is made of a lens which when focused on a body, collects rays of light from it. The lens is made of either glass or plastic (either way its refractive index must be such that light rays travel slower than it normally would when travelling in air) the lens is then focused on a surface, the light ray would then a cast a shadow of the object on a surface, this surface is called a photographic paper or “film” which happens to be a light sensitive as it is made of light-sensitive materials like SIlver.
Well in the case of TV cameras which happens to be synonymous to the digital camera, Light reflected from the object to the camera lens the picture formed then goes into the image sensor chip;
What the sensor chip does is to break the incoming picture generated into millions of pixels, and stores it in electronic format, it is this digital format that makes it transferable from one point to another via electronic channels like USB cables and other wireless mediums.
As said earlier, videos are faster stream of moving pictures, a video shows about 24 different pictures in a second which makes motion capture a reality.
SO WHAT’s NEXT ? (TV TRANSMITTER)
Having generated the electronic signal with our TV camera in the football pitch, it is therefore desired to transmit through long distances in real time all over the world;
What then is the best method to achieve this? Before I answer the obvious question I will first explain some basic modes of TV broadcasts
Let’s see some few TV broadcast methods
There are various means through which television broadcast is carried out, the earliest of this methods is the
Analogue Terrestial TV or Aeriel transmission: Unlike our modern day system, it doesn’t require the use of underground cables or satellites’. Like a radio station, what the analogue transmitter does is simply to transform the sound and image (a process called encoding) intan a analogue signal, this signal is called the modulating signal, for transmission purposes, the signal needs to be modulated.
Modulation involves a superimposition of a sinusoidal signal on the signal to be transmitted.
The sinusoid in which the modulating signal is mixed is called the carrier signal the carrier signal has no information inside it but is used to modify the message signal into a desired parameter to make it suitable for transmission. I could continue to talk and talk about modulation (Maybe I will do something on that soon) but do note that the main parameters that are modified during modulation is either the amplitude (amplitude modulation) frequency (frequency modulation) or phase (phase modulation)
Remember that a signal is described by the equation
F(t) = Asin(wt+Φ)
Where w=2πf.
TV broadcasts is modulated using UHF (Ultra high frequencies) or (VHF) very high frequency, Because UHF and VHF’s are used, gigantic antennas are not required to intercept this is one of the major advantages of UHFs. UHF has high radio frequencies rangong from 300MHz-3GHz while VHF has frequencies ranging from 169-216MHz.
Note that every Local Television station transmits at particular frequencies, I remember when I was much younger, i always loved to search my TV set to check for new channels because of their interesting programs, I never knew what I was doing then was browsing through different frequencies. Lol
CABLE TV NETWORK:
Also known as Community Antennae Television (CATV) this a broadcast method which involves using cables to transmit television signals within a community, like an electrical distribution system which uses distribution transformers to transmit electricity from one end to another via Low tension cables, the cable tv network has a central location that serves as a receiver of several television systems and transmit locally through coaxial cables from one house to another.
The image below shows model of such networks;
Cable Televison network; Wikimedia commons CCSA 2.5
At this point, I expect us to start wondering that if local television stations are limited by space in a sense, e.g its not possible to get a real-time live broadcast from Russia down to Nigeria through any of this s aforementioned mediums. Therefore, how does the technology that brings about real-time television broadcast from one end of the world to another work?
Certainly, you don’t expect any of the aforementioned broadcast method to work, and please don’t mention the internet as we have already differentiated livestreaming from live-broadcast.
Okay so lets cut the suspense short now
SATELLITE TV TECHNOLOGY (The answer to the question)
We are taking our cue football matches, one thing am so sure of is that there is hardly any football fan reading this that is not conversant with Super Sports 3, SS3. Well SS3 amongst numerous is a TV station that shows football matches. Notice that football matches are much clearer when you watch stations like that as opposed to the conventional aerial broadcast system. Let me go on to explain how it works;
THE PROGRAMMING SOURCE: It starts from channels like SS3, CNN, Disney Jnr, SELECT etc. they are called broadcasting companies, of course having access to a TV camera which as previously stated is used in broadcasting this live events, Note that they don’t necessary have to broadcast live events, they could function like a normal HDTV station (which they do most of the time). The programming source will therefore transmit signals via cables or wireless system to the broadcasting centers
THE BROADCAST CENTRES: This is a company that receives signal from the multiple programming sources, examples of such companies is what we know as the DSTV, HITV, SPACE etc. in this companies, 2 major operations happens, they are
Compression: Various signals coming from the programming sources (Stations) are compressed to about 60% of the original signals, a multiplexer is used to collect several signal input from different sources and give a single/fewer output, this output is the one that is compressed
Protection by encryption: You know, what gives you access to use this services is your paid subscription, the service therefore has to be shielded from non-subscribers; that’s where the magic happens.
Once those two things has happened, then it is time to transmit it.
Where do we transmit it to?
GEO-STATIONERY SATELLITES
Our dear encrypted and compressed signals is transmitted to a geostationary satellite.
A geostationary satellite is a satellite mounted in space (about 38500Km above the sea level)
One spectacular feature of this satellite is that it is engineered in such a way that it moves at the same period as the earth's rotation about the sun in its orbit i.e it takes the satellite 24 hours to rotate around it orbits like the earth. This unique feature makes the satellite to appear stationery while viewing it from the position of the earth. A single geostationary satellite can cover about 40% of the surface of the earth.
In the satellite we have a number of transponders on the satellite, what the transponders do is to receive the signals transmitted by the broadcast centers and rebroadcast it.
The frequency of this signal is very high at this point; in fact it is now a microwave
Remember;
V=fλ, therefore frequency is inversely related with the wavelength as f=v/λ as v is the speed of light, that is why microwaves have small wave-lengths but high frequency
That is where your satellite dish comes in.
SATELLITE DISHES what do they do and why are they placed outside? :
This satellite dish receives the retransmitted signal from the transponder, as said earlier the wavelength coming from the transponders in space is so low, (between 1cm -10cm) though can penetrate your wall, but wouldn’t be able to deflect as your home wall I certainly thicker than 10cm, however an AM receiver having longer wave length can be placed inside your house, even certain UHF’s cannot be picked if the UHF receiver is inside the house.
This satellite dish has a parabolic surface which is used to collect this high frequency micro-waves, the higher the surface area, the higher strength of the signal, the rays of the dish deflects the microwave into a feed-horn which is located at the focal point of the parabolic dish, just like a concave mirror does. One major advantage of using dishes is the fact that the dish would receive clear signals owing to the fact that in ideal conditions there are no obstacles between the satellite and the dish.
The feed horn has a Low Noise Blockdown converter which filters out the noise (signals with no information), amplifies the signal and ultimately, converts the signal to a low frequency which is compatible with the decoder. The signal is then transmitted through an LNB cable which is coaxial in nature into the receiver.
FINALLY, THE DECODER
The receiver/decoder is that device that receives the low-band frequency and amplified signal from the feed horn through the LNB cable. The decoder simply reverses everything one to the signal from the broadcast centres, i.e. Decompression and decryption (of course only active subscribers would be granted the permission to do so) not only that the signal is also processed and separated into the different channels as many sources are fed into the broadcast centers.
CONCLUSION
Sattelite broadcast technology gives high definition signal, because of the geostationary satellites, it is much easier for electromagnetic wave to travel freely in space, however it is very costly to execute such project, thats why most satelite tv companies/centers require subscription to access.
REFERENCES
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