Page 260 - Satellite Communications, Fourth Edition

240 Chapter Eight

for the Ku-band signals. Much of television programming originates as
first generation signals, also known as master broadcast quality signals.
These are transmitted via satellite in the C band to the network head-
end stations, where they are retransmitted as compressed digital signals
to cable and direct broadcast satellite providers. One of the advantages
claimed by sellers of C-band equipment for home reception is that there
is no loss of quality compared with the compressed digital signals.
To take full advantage of C-band reception the home antenna has to
be steerable to receive from different satellites, usually by means of a
polar mount as described in Sec. 3.3. Another of the advantages, claimed
for home C-band systems, is the larger number of satellites available for
reception compared to what is available for direct broadcast satellite sys-
tems. Although many of the C-band transmissions are scrambled, there
are free channels that can be received, and what are termed “wild feeds.”
These are also free, but unannounced programs, of which details can be
found in advance from various publications and Internet sources. C-band
users can also subscribe to pay TV channels, and another advantage
claimed is that subscription services are cheaper than DBS or cable
because of the multiple-source programming available.
The most widely advertised receiving system for C-band system appears
to be 4DTV manufactured by Motorola. This enables reception of:

1. Free, analog signals and “wild feeds”
2. VideoCipher ll plus subscription services
3. Free DigiCipher 2 services
4. Subscription DigiCipher 2 services
VideoCipher is the brand name for the equipment used to scramble
analog TV signals. DigiCipher 2 is the name given to the digital compres-
sion standard used in digital transmissions. General information about
C-band TV reception will be found at http://orbitmagazine.com/ (Orbit,
2005) and http://www.satellitetheater.com/ (Satellite Theater systems, 2005).
The major differences between the Ku-band and the C-band receive-
only systems lies in the frequency of operation of the outdoor unit and
the fact that satellites intended for DBS have much higher equivalent
isotropic radiated power (EIRP), as shown in Table 1.4. As already men-
tioned C-band antennas are considerably larger than DBS antennas. For
clarity, only the Ku-band system is described here.
Figure 8.1 shows the main units in a home terminal DBS TV receiv-
ing system. Although there will be variations from system to system, the
diagram covers the basic concept for analog [frequency modulated (FM)]
TV. Direct-to-home digital TV, which is well on the way to replacing
analog systems, is discussed in Chap. 16. However, the outdoor unit is
similar for both systems.