Category Archives: Satellite

VSAT

VSAT, which stands for Very Small Aperture Terminal, is a type of satellite technology. As the name suggests, it consists of a two-way satellite structure set up on level ground. VSAT makes use of a dish antenna. This dish antenna is not larger than 3 meters. Most dish antennas used by the VSAT technology have sizes ranging from 75 centimeters to around 1.5 meters.

VSAT is applied in several technologies. Certain systems providing point of sale services for credit cards use VSAT to initiate and complete the transactions. Remote satellite Internet access and Voice Over Internet Protocol (VoIP), as well as devices used in mobile maritime operations also use VSAT technology.

VSAT uses a set of advanced technologies to provide data transfer and other functions. It uses satellite broadcasting technologies including high-powered components and antennas. These antennas have a much higher precision than those used by satellite television systems. VSAT also uses a receiver and a transmitter to send data back to the main satellite.

Furthermore, VSAT can be configured in a number of network topologies, for example, a star topology with a central site. This central site transports data to and from each terminal using the satellite. Aside from this, a mesh topology can be used in VSAT. Instead of using a central site, each terminal in a mesh topology acts as a hub and relays data through a satellite. Additionally, a combination of star and mesh topology can also be used in VSAT. In this setup, the stars and their central sites are connected to each other through a mesh topology.

FSK

FSK stands for Frequency Shift Keying. It is a modulation scheme where a specific source transmits digital information through discrete changes in a carrier wave frequency.

FSK has a number of classifications. BFSK, or Binary Frequency Shift Keying, is the simplest among these classifications. As its name suggests, BFSK makes use of two distinct frequencies to transmit binary information: 0s and 1s. The 1 refers to the mark frequency while the 0 refers to space frequency.

The other forms of FSK are:

  • Minimum Shift Keying, also known as MSK, is believed to be a more efficient form of FSK. This is because in FSK, the difference betwe en the lower frequency and higher frequency is the same as half the bit rate. This results to the 0 and 1 waveforms having half a carrier difference.
  • Audio Frequency Shift Keying, otherwise known as AFSK, is another form of FSK. In AFSK, digital information is represented as changes in the frequency or pitch of a particular audio tone. This yields a signal suitable for radio or telephone. The transmitted audio normally shifts between two tones: the mark and the space.

FSK is implemented in many systems and applications. The early telephone modems, for instance, use FSK to transfer and receive data. Caller ID systems also use FSK to register the necessary information.

In addition, FSK plays a major role in storing data on audio cassettes used for recording. Also, FSK is used in amateur radio that usesdata transmission via unmodified voiceband equipment.

Free to Air

Free to Air is a term used to describe unencrypted radio and television broadcasts. These broadcasts allow households with a satellite dish to receive the satellite signals legally even without subscription. These broadcasts may have geographical restrictions. It is often encoded for MPEG-2 video.

Free to Air is often used for international broadcasting. It is a subset of TeleVision Receive Only (TRVO), and was formerly transmitted on C Band. Some parts of the world obtain encrypted Free to Air satellite channels on VHF and UHF frequency bands.

Nowadays, most television networks in the US are not available unless one has a satellite dish service or cable subscription, which are both able to break encrypted codes. If programming is broadcast via satellite and one has no satellite dish, Free to Air programming may be hard to acquire. Few stations still use previous broadcasting methods; thus, TV ear antennas have been widely replaced.

There are still numerous Free to Air radio broadcasts obtainable without having to subscribe to a satellite radio service. Majority of radio programs are broadcast in a Free to Air format. Excluding public radio, listeners must bear with frequent commercial interruptions. Some listeners may prefer to pay a fee that enables them to obtain uninterrupted programming.

Even now, majority of television stations with Free to Air format pause for commercial breaks or notification for sponsorships, with the exclusion of stations like PBS, an educational broadcaster. PBS does hold pledge drives wherein the station broadcasts its most popular programs with long breaks to plea for people’s support to the network.

Free to Air satellite television is fitting for areas where terrestrial reception is a problem. This is because it has wide-ranging geographical coverage even in locations where terrestrial signal reception is weak, such as those in rural areas, which are very distant from major cities.

To receive Free to Air satellite broadcast, you will need a satellite dish antenna, an antenna motor, an FTA receiver or satellite PC card, and a Low Noise Block Converter.

Additional Reading on Free To Air Television

LNB

An LNB or low-noise block converter (sometimes called LNC) is the antenna used for communications satellite TV reception. It is usually attached on or in the satellite dish. Although LNB is waveguide-based, it functionally corresponds to a dipole antenna used for majority of TV reception purposes.

While the dipole antenna is not able to settle in various polarization planes without rotating, the LNB can be electronically changed between vertical and horizontal polarization reception. Its satellites utilize relatively high radio frequencies to send their signals.

Function of LNB

LNB is used to employ the super heterodyne effect, augment a wide band (or block) of frequencies, and convert them to signals transmitted at a much lower intermediate frequency.

The intermediate frequency would travel through cables with less reduction of the signal, so there are more signals for the receiver of the cable.

Developing electronic circuits to work at these lower frequencies instead of operating at very high frequencies is easier and less expensive. This also assists in compensating for lost signal because of typical coaxial cable at comparatively high frequencies.

Features of LNB

The term ‘low noise’ is related to the feature of the special engineering used – the 1st stage of the input amplifier transistor. This is measured in Noise Figure Units, Noise Factor Units, or Noise Temperature Units. Low noise also means that mixing and amplification happen before the cable attenuation in a circuit that does not require a power supply or receiver.

Both Noise Figure and Noise Factor are easily converted into Noise Temperature Units. A lower rating in the Noise Temperature is always better.

The word “block” describes the change of a superior block of microwave frequencies to the receiver’s inferior block range of microwave frequencies.

The low-noise block converter helps keep the overall picture and audio of the satellite TV from being degraded. This is done without having to introduce a much larger dish reflector.

For wide bandwidth satellite TV transporter signal, the accuracy of the local oscillator frequency of the LNB has to be more or less 500KHz. This would make an economical dielectric oscillator (DRO) viable.

However, for reception narrow band satellite television carriers, a low-phase noise and highly stable local LNB oscillator is needed.

Additional Reading on LNB

Free to Air Channels

Free to air is an expression describing radio and television broadcasts that enable viewers to pick up the signals without subscribing to cable services. Free to air channels are obtained using a common MPEG-2 video compatible satellite receiver. It corresponds to shortwave radio.

Free to air television programming is frequently used for international broadcasting. It is different from the television channels available on cable TV or Direct Broadcast Satellite (DBS). In countries other than the US, much of television programming may be free to air.

Most television and satellite radio programming in Europe is in free to air format. Key TV networks are primarily free to air and Europeans may seldom request for pay per view episodes. However, the XM-style and Sirius reception is not possible because of the employed satellite broadcast systems.

Germany takes pleasure in having more than 100 free to air TV channels including MTV. Most TV channels on major corporate subsidiaries’ geostationary satellites are free to air.

In North America, there are several sources for free to air satellite television. US satellites carry most of the free to air signals. A number of satellite dish manufacturers enable individuals to receive free to air channels even from apartment balconies.

Years ago, it was difficult to find free to air channels in South America, except for Venezuela and Mexico. Today, Latinos enjoy more than 100 channels in free to air format.

Australia has 6 free to air TV networks transmitting to chief urban areas. These include ABC, SBS, Network Ten, Seven Network, Nine Network, and Community television channels. Various regional affiliates of these companies cater to rural portions of the country.

In South Asia, a number of free to air TV channels are transmitted to several countries such as China, Myanmar, India, Pakistan, Bangladesh, Nepal, Sri Lanka, etc.

In South Korea, free to air channels dominate 80% of advertisement profits. Free to air channels in the country include EBS, KBS, and MBC.

TV Asahi and TV Tokyo of Japan are some of the television broadcasters in the country that heavily rely on sponsorship.

Although free to air viewing may be free, it is not the same for the broadcasting network. All television and radio companies must pay for licensing fees to operate. Some pirate TV and radio networks exist but their spots are frequently revealed and shut down.

When pioneering radio and TV stations started, nearly all programming of major stations were in free to air format and were viewed by those in close proximity to broadcast antennas.