Recently I was in my building terrace, since I always love to click tech photo. When I looked down I saw houses have parabolic satellite television antenna. It was like cluster of about 10-15 antennas on one side.
Later I found I Tata sky antenna on my building too. Immediately question strike in my mind how this antenna actually works. I have a cable operated TV, how it’s different from satellite TV?
View from Terrace with around 10-15 satellite dish antenna
#1. Broadcasting TV and its Limitation
Broadcast television stations transmit programming via a radio. Broadcast stations use a powerful antenna to transmit radio waves to the surrounding area. Viewers can pick up the signal with a much smaller antenna.
Radio signal broadcasting tower
Limitation of broadcast TV.
- The most important limitation of broadcast TV is its range.
- In order to receive signals, you have to be in the direct line of sight of the antenna. Small obstacles like trees or small buildings aren’t a problem, but a big obstacle, such as the Earth, will reflect these radio waves.
- If the Earth were perfectly flat, you could pick up broadcast TV thousands of miles from the source. But because the planet is curved, it eventually breaks the signal’s line of sight.
- The other problem with broadcast TV is that the signal is often distorted, even in the viewing area. To get a perfectly clear signal like you find on cable, you have to be pretty close to the broadcast antenna without too many obstacles in the way.
#2. Cable TV and its Limitation
Cable television is a system of delivering television programming to paying subscribers via radio frequency (RF) signals transmitted through coaxial cables, or in more recent systems, light pulses through fiber-optic cables.
Digital cable distribution using digital video compression audio and video plugin
This contrasts with broadcast television, in which the television signal is transmitted over the air by radio waves and received by a television antenna attached to the television; or satellite television, in which the television signal is transmitted by a communications satellite orbiting the Earth and received by a satellite dish on the roof
Limitation of Cable TV but it still works
- There has to be a cable TV operator in area who provide you connection to your TV. Therefore remote villages, hilly regions etc. might not have cable TV option.
- Low Quality and not many channel options.
- Increased service costs as your provider updates.
#3. Satellite TV is the Solution
Satellite television is a service that delivers television programming to viewers by relaying it from a communications satellite orbiting the Earth directly to the viewer’s location. The signals are received via an outdoor parabolic antenna commonly referred to as a satellite dish and a low-noise block downconverter.
The satellites used for broadcasting television are usually in a geostationary orbit 37,000 km (23,000 mi) above the earth’s equator. The advantage of this orbit is that the satellite’s orbital period equals the rotation rate of the Earth, so the satellite appears at a fixed position in the sky.
Satellite in geostationary orbit revolving with earth direction i.e West to East
The concept of the geostationary communications satellite was first proposed by Arthur C. Clarke, along with Vahid K. Sanadi building on work by Konstantin Tsiolkovsky.
#4. First Geostationary Communication Satellite
Telstar is the name of various communications satellites. The first two Telstar satellites were experimental and nearly identical. Telstar 1 launched on top of a Thor-Delta rocket on July 10, 1962.
On June 19, 1981 India launched its first geostationary satellite called APPLE. It was an experimental communication satellite launched by the Indian Space Research Organisation (ISRO) with a C-band transponder.
APPLE: Indian First Communication Satellite(Image source:ISRO)
#5. Working Principle of Satellite Television
Satellite television relayed by satellite, starts with a transmitting antenna located at an uplink facility. Uplink satellite dishes are very large, as much as 9 to 12 meters (30 to 40 feet) in diameter. The uplink dish is pointed toward a specific satellite and the uplinked signals are transmitted within a specific frequency range, so as to be received by one of the transponders tuned to that frequency range aboard that satellite.
The transponder re-transmits the signals back to Earth at a different frequency (a process known as translation, used to avoid interference with the uplink signal), typically in the C-band (4–8 GHz), Ku-band (12–18 GHz), or both. The leg of the signal path from the satellite to the receiving Earth station is called the downlink.
#6. Satellite Dish Antenna?
A satellite dish is a dish-shaped type of parabolic antenna designed to receive or transmit information by radio waves to or from a communication satellite. The term most commonly means a dish used by consumers to receive direct broadcast satellite television from a direct broadcast satellite in geostationary orbit.
The viewer’s dish picks up the signal from the satellite (or multiple satellites in the same part of the sky) and passes it on to the receiver in the viewer’s house.
#7. First Person to receive Satellite Television
In 1975 Stephen J Birkill, a BBC transmitter engineer became first person to receive satellite television with its homemade satellite dish in its backyard. India were working ton NASA satellite ATS-6 to transmit television program to remote Indian villages.
Stephen noticed signal are transmitted to other subcontinents. Then Stephen built electronic circuitry to receive these signal on its kitchen.
Stephen Birkill in the 1970s with his homemade satellite television equipment(Source: star.co.uk)
#8. About FTA?
Free-to-air (FTA) are television (TV) and radio services broadcast in clear (unencrypted) form, allowing any person with the appropriate receiving equipment to receive the signal and view or listen to the content without requiring a subscription, other ongoing cost.
Around 600 FTA television channels and 180 Radio Channel are broadcast from ku-band and c-band transponders on the INSAT-4B and GSAT-15 satellite covering India, Pakistan, Bangladesh, Bhutan, Nepal, Sri Lanka and parts of Afghanistan, China, and Myanmar.
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