Satellite Television communication requires the transmission of program data over radio waves. The audio-video program is converted to electromagnetic form.
This data is transmitted from one earth station to another. In the case of Satellite Television communication, the data is transmitted from one Head-end to a Geo stationary satellite, the Satellite receives the data, does the necessary amplification, and then re-transmits it to earth stations, over a larger area on the earth’s surface.
In some cases, end users can also receive the data using ordinary dish antennas. This depends upon the freq and symbol rate of the transmitted data.
View Now
Types of transmissions in tv communication
- L-Band
- C-Band
- Ku-Band
- Ka-band
The satellite high gain bands used for a particular purpose depend upon commercial and technical factors. Suppose a DTH company uses the Ku band, while bigger enterprises with lesser receiving stations use the C BAND news gatherers used ka band, and so on.
Below are details of each of these four bands.
L-Band –
L-Band (1-2 GHz) being a relatively low frequency, L-band is easier to process, requiring less sophisticated and less expensive RF equipment, and due to wider beam width, the pointing accuracy of the antenna does not have to be as accurate as of the higher bands.
L band used by Global Positioning System (GPS), radio, telecommunications, aircraft surveillance, etc
C-Band –
C-Band hardware is significantly more expensive while the capacity is cheaper. So customers with large bandwidth requirements preferably choose this technology.
Ku-Band –
Ku-Band on the other hand operates with smaller antennas and less expensive equipment, while the signal capacity price is higher than C-Band.
Ka-Band –
The Ka-band provides an increased spectrum compared to C-band and Ku-band, enabling greater volumes of traffic to be transmitted.
Many industries are looking to Ka-band because the smaller end-user antennas (VSATs), increased mobility and higher bandwidths and speeds make the benefits of Ka-band satellite capacity an attractive offering.
Pros & Cons –
L-Band (1-2 GHz)
Advantages:
- Less disturbance from heavy rain fade
- Less expensive hardware can use smaller antennas
Disadvantages:
- Only a small portion (1.3-1.7GHz) of L-Band is allocated to satellite communications on Inmarsat.
- Since there is not much bandwidth available in L-band, it is a costly commodity.
C-Band (4-8 GHz)
Advantages:
- Less disturbance from heavy rain fade
- Cheaper Bandwith
Disadvantages:
- Needs a larger satellite dish (diameters of a minimum of 2-3m)
- Powerful (=expensive) RF unit
- More expensive hardware
- Possible Interference from microwave links
Ku-Band (12-18 GHz)
Advantages:
- No interference from microwave links and other technologies
- Operates with a smaller satellite dish (diameters from 0.9m) -> cheaper and more easy installation
- Needs less power -> cheaper RF unit
Disadvantages:
- More expensive capacity
- Sensitive to heavy rain fade (significant attenuation of the signal) / possibly can be managed by appropriate dish size or transmitter power.
Ka-Band (27-40 GHz)
Advantages:
- Higher speeds
- Operates with a smaller satellite dish (diameters from 0.9m) -> cheaper and more easy installation
Disadvantages:
- When high frequencies are transmitted and received in a heavy rainfall area, noticeable signal degradation occurs and is proportional to the amount of rainfall.
- Downlink: Rain dissipates 3 to 10 times more energy at Ka-band than at Ku-band (11 GHz vs. 20 GHz)
- Uplink: Rain dissipates 63 to 400 times more energy at Ka-band than at Ku-band (14 GHz vs. 30 GHz)
- Ka-band is not available everywhere.
