The existence of open channels offers consumers another possibility to access free television and radio services complying with the basic premise of entertainment that users are looking for as an alternative to cable and DTH or DBS systems. As noted in the first part of this article, the system is available and consists of certain elements that make it possible to receive signals, we will delve a little deeper into the subject showing its operation and comparing it with other alternatives so that you decide which option is the best according to your needs.
How does the satellite transmission system work?
The satellites are located in the geostationary orbit of the earth, approximately 22300 miles from the surface, in direct communication with the antennas to transmit and receive signals. Transmission programmers send ( uplink process) signals to the satellite which may or may not be encrypted; the encoding is done to avoid unauthorized receptions of the signal before being sent to the antennas of the users. The signals are received by a transponder located on the satellite, which is responsible for retransmitting them after having converted the signal to the frequency programmed for the antennas on the ground.
Typically a satellite has 24 to 32 transponders that transmit different numbers of channels depending on the type of compression and the desired signal quality, usually the average is ten channels. In order to minimize interference between transponders, signals are transmitted alternately to polarized antennas.
The signal sent back is received by the antenna but with a minimum amplitude, less than one watt, which requires the use of amplifiers (LNBs) to reset the signal to a frequency that can be processed and retransmitted on the ground. A C-band satellite transmits with a power range of 10 to 17 watts per transponder and requires antennas 5 to 10 feet in diameter for amplification, while a satellite that transmits in Ku-band, with a range of 100 to 200 watts per transponder requires antennas of 18 inches in diameter.
With its new amplitude, the signal passes to the IRD (Integrated receiver/decoder) where it is transformed into a format that can be viewed on a TV. Each IRD or decoder has a unique serial number that identifies it, which is activated by the satellite programmer to allow the reception of encoded signals. In the case of free channels, the signal goes through a decompressor that converts it to a television format. When services that require two-way communication are provided, the IRD is usually connected to a telephone line that completes the return process.
To be able to see multiple signals at the same time, the system requires adaptations that vary depending on the number of signals received and the number of receiving units connected. For example, if you want to watch two different programs in two separate units, you will need two IRDs (receivers) and an antenna that has double LNBs; a single LNB will allow you to receive signal from a single satellite and a double one will give that single signal to two receivers. If you receive a signal from more than one satellite, you will require an associated satellite LNB . On the other hand, if you need to connect more than one receiving unit to a single antenna you will need a switch (switcher) for each additional unit.
In this way you can connect to your system three types of antennas that are:
- Simple LNB antenna : will allow you to connect a single receiver and receive a single signal.
- Dual LNB antenna : will allow you to connect two receivers and receive signal from a single satellite.
- Multi-location antenna: it has two LNBs that receive independent signals and the number of associated receivers depends on whether the LNB is single or double or the use of switchers.
In which satellites are there free channels?
As mentioned in the first part, the possibility of finding open channels is very large, about two thousand are already available and the number is increasing, visiting the page
www.commsearch.com/canalesespa.htm you can find a detailed list of satellite channels which is constantly updated.
Among the satellites that transmit these signals are: SATCOM C-3 and C-4, TELSTAR 4, 5 and 7 C and Ku band, GALAXY 1-R, 5 and 10R, ECHOSTAR 3, 4 and 5, PanAmSat 3, 5 and 9, INTELSAT 706, 709 and 805, SATMEX 5, BRASILSATS and NAHUEL from Argentina available only for South America, HISPASAT available for America only, COLOMBIA 515, and TDRS 5 (inclined), PANAMSAT 2 and INTELSAT 701 that are not seen in South America.
What is DBS and DTH and how are they different from free receiving systems?
Direct Broadcast Satellite (DBS) and Direct To Home (DTH) are two terminologies that mean basically the same thing, the reception of television programming directly from the satellite, in most cases, is associated with pay TV systems. The difference with systems that receive open signals lies, apart from the non-payment for the signal received, in the antennas used, the type of receiving device and the services received through the satellite.
The type of antennas for DBS and DTH are not compatible with the antennas used in open systems, these are of greater size, capacity and price. The antennas for DBS are approximately 60 centimeters or 18 inches in diameter and stationary (they do not have a positioner or actuator) which does not allow them to receive many of the open signals, in addition, the transmission frequencies are different and unrepeatable and the satellite only sends the signal to pre-identified ground stations. Additionally, until now there is no DTH or DBS service that allows its users to receive signals from different satellites.
On the other hand, the receiving apparatus partially prevents this function, these units are previously programmed to decode a unique type of signal that is not compatible with the compression of open signals. The channels received are identified and the possibility of adding more is given only in the type of receivers for open signal. On the other hand, DTH operators do not give the possibility to their subscribers to program new channels in their units, which does not mean that a receiver that can accept open and closed signals is not on the market, an example of this is the 4DTV unit that is compatible even with interactive services and internet access. On the other hand, receivers for DTH are more advanced as they require special cards to make it possible to receive interactive services.
As for services, open systems have a single signal reception service, while DTH systems have among others: television services, transaction applications such as sales or credit card verification, interactive applications such as programming guides, dial-up and internet access, corporate networks, etc.
Some advantages and disadvantages of satellite compared to cable networks:
The main competitor of satellite systems is the traditional cable television service, whose main advantage is the reduced cost. However, satellite systems offer as their greatest attraction an unlimited number of channels. Among other advantages offered we can find an unlimited coverage of area regardless of whether it is rural, 100% digital quality in video and sound thanks to direct transmission, the possibility of adaptation to different time zones of the programming, and the null possibility of signal deterioration and the lower risk of service interruption, thanks to the fact that the system does not depend on a terrestrial infrastructure.
As for the disadvantages of the satellite, there is a momentary interruption of service caused by atmospheric phenomena such as strong storms, a phenomenon known as "rain-fade" that interrupts the straight-line transmission of the signal between the satellite and the antenna. Finally the higher cost of the equipment required for this service limits many users to access the satellite system, however, the advancement of technology is causing costs to be reduced, for example, in relation to antennas and their sizes, and the need for several receiving units to view and store different signals.
In conclusion, the viewer has several options when choosing with which method he wants to receive his television signal, it will depend on the tastes of each one if he decides to become a subscriber who assumes a monthly charge in exchange for services with added value, or if you decide to take advantage of the countless open channels sacrificing the convenience of personalized and interactive services. As in all options, there are advantages and disadvantages in each and the passage of time, the development of technology and the tastes and needs of the client will determine which will survive the choice.
