satellite television 1 it’s out of sight! 22,300 miles in fact!
TRANSCRIPT
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Satellite Television 1
Satellite TelevisionSatellite Television
It’s out of sight!
22,300 miles in fact!
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Satellite Television 2
From How Stuff WorksFrom How Stuff Works
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Satellite Television 3
20 + Commercial Satellites20 + Commercial Satellites
In Geo-Stationary Orbit 22,300 miles away....
All in a band over the EquatorThey have a revolution of once per day. Just like us!... That makes them geo-
stationary.They have a useful life of 10 years.
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Satellite Television 4
Boeing 702the most widely used
satellite
Boeing 702the most widely used
satellite
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Satellite Television 5
Hughes HS601Hughes HS601
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Satellite Television 6
Forces at workForces at work
A satellite spins around the planet
What holds these satellites in place ?Gravity will try to pull the mass back to
earthThe force of a centrifuge pushes the
satellite out into space ..
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Satellite Television 7
Geo-stationary OrbitsGeo-stationary Orbits
The force of gravity, Fg, is equal toThe centripetal force, FcAT 22,300 miles, Fg = Fc if the velocity
is one revolution per day !This was first proposed byArthur C.
Clarke...
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Satellite Television 8
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Satellite Television 9
The Clarke BeltThe Clarke Belt
These satellites appear to be in the same position in the sky at all times.
They are directly over the equator but not directly over us.
They are in a line that starts 14 degrees above our Western Horizon.
And rises to 42 degrees elevation in the South
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Satellite Television 10
Original figure from Clarke's article in the October
1945 edition of Wireless World Original figure from Clarke's article in the October
1945 edition of Wireless World
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Satellite Television 11
Elevation and AzimuthElevation and Azimuth
The Elevation is the number of degrees above the horizontal...
The Azimuth is a degree reading with North being 0 and 360 degrees, East being 90, South at 180, and West at 270.
Degree readings are allways ‘True’ and not ‘Magnetic’
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Satellite Television 12
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Satellite Television 13
Uplink antenna
Elevation and Azimuth are adjusted to point to the satellite
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Satellite Television 14
24 Channels on a Satellite24 Channels on a Satellite
Numbered 1 to 24Odd Number Channels are often
Vertically Polarized...Even Number Channels are often
Horizontally Polarized.The antenna must line up with the
polarization..
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Satellite Television 15
C Band and Ku BandC Band and Ku Band
The C Band uses 4 GHz for the down link and 6 GHz for the up link.
The Ku Band uses 12 GHz for the down link and 14 GHz for the up link.
A ground station monitors each satellite 24 hours a day.
Friction tends to move them from their orbit ! (Magnetic friction..)
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Satellite Television 16
A ‘downlink’
Much less expensive than the uplink ..
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Satellite Television 17
Analog vs DigitalAnalog vs Digital
The largest commercial system is an Analog system, subject to noise and signal strength.
The newer Digital dishes can easily remove the nose and can produce crystal clear pictures with weak signals.
The Digital dishes are smaller..
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Satellite Television 18
A digital dish ..
MPEG2 is used as a format for the data stream ..
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Satellite Television 19
A satellite uses 300 WattsA satellite uses 300 Watts
Which must come from solar powerThis power is distributed over 24 small
transmitters...The surface area of the US is 3,000,000
Square Miles.That’s 100 Micro Watts per square mileBut only 5 Micro Watts per channel...
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Satellite Television 20
The signals are very very weak.
The signals are very very weak.
A large ‘dish’ is used to focus the power received onto a small 1.5 CM antenna..
A 12 Foot dish, has an area of Pi X R2 or 108 Sq Feet.
Calculate the power the dish receives from a 300 Watt Satellite....
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Satellite Television 21
An 18” Digital Dish...An 18” Digital Dish...
Has a much smaller surface areaReceives a much smaller amount of
power...But delivers a better signal due to the
cleanliness of ‘bits’ !
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Satellite Television 22
Satellite ‘Sighting’Satellite ‘Sighting’
We point the dish at specific azimuths and elevations to find a satellite.
From 14 Degrees Elevation and 270 Degrees Azimuth (W)
To 42 Degrees Elevation and 180 Degrees Azimuth (S)
A set of tables lets us find the data for a particular satellite.
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Satellite Television 23
Latitude and LongitudeLatitude and Longitude
Binghamton... Is at 70 Degrees E Longitude and 42
Degrees N LatitudeEast of Grenich, and North of the
EquatorThe calculations for finding a satellite
22,300 miles over the equator are complex
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Satellite Television 24
Longitudes for US ViewLongitudes for US View
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Satellite Television 25
A recent copy of ORBITA recent copy of ORBIT
Shows us the longitude of the various satellites.
They are spaced 3 to 6 degrees apartTheir longitude, entered into an
equation gives us Elevation and Azimuth.
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Satellite Television 26
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Satellite Television 27
The Satellite RECEIVERThe Satellite RECEIVER
The signal is collected by the ‘dish’Focused on the ‘Feed Horn’ AssemblyAmplified by a Low Noise AmplifierConverted to a much lower frequencyCarried by shielded cable to the
receiverAnd delivered to your TV set..
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Satellite Television 28
Satellite Feed Horn AssemblySatellite Feed Horn Assembly
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Satellite Television 29
The ‘Polarotor’The ‘Polarotor’
A small motor turns the antenna to accomodate the ‘polarization’ of the signal.
The ‘plane’ of the signal ‘skews’ as we point the dish to the west
The ‘polarotor’ must compensate for this skew
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Satellite Television 30
SatellitesSatellites
Are also used for ‘Pager Service’Cellular TelephoneOther types of communication including
the monitoring of vehicles like Federal Express
Global Positioning ( GPS)
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Satellite Television 31
Satellite in low Earth OrbitSatellite in low Earth Orbit
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Satellite Television 32
For more .. Go to the web ..For more .. Go to the web ..