In any satcom system, there are some fundamental building blocks. This diagram shows these blocks in a basic form to help you understand what they are.

Suppliers

Where ever the data to be transmitted via satellite is coming from is the supplier base. this could be anything from an outside broadcast unit to a studio or office complex. Even banks or communications headquarters.

Bearers

In order to get this data to the teleport for onward transmission via satellite, we use a bearer. The most commonly used bearer supplier is BT but they are not the only supplier of such communications. Many forms of bearer exist and are mainly fibre optic high speed lines or lower speed kilostreams and even permanent leased line (telephone line) connections.

Bearers can be occassional use such as 64k or 128k ISDN lines. Even the internet can be used for some applications.

The end aim is to deliver error free data to the teleport.

Teleports

Once the data arrives at the teleport then it is passed to a satellite modem or multiplexed with several other data streams before reaching the modem. The modems then give an intermediate frequency output (I.F.) which are adjusted for level and frequency before entering the RF system which contains the up conversion, filters and high power amplifiers. The signal containing the suppliers data is then braodcast to the satellite through one or more antennae at the teleport. More than one antenna is used if the data is required on more than one satellite to increase coverage.

Subscribers

Finally the signal is received back on earth at the subscriber terminal. This could be a large VSAT for distribution of many data streams or a small terminal such as a Sky TV system or video conferencing system.

This whole system can be two way or one way depending on the requirements. Broadcasting is usually one way and point to point transmission is usually two way.

The principles are the same for all satellite systems however big or small.