Satellite Dishes:

A typical commercial cable plant (if used for distributing both television and Internet signals) will have five to seven satellite dishes to capture the signals and send them to receivers. Some of these dishes will require that matching receivers be joined to them, while others will work with generic receivers. (For example, bell expressview dishes require that bell expressview receivers be used, and starchoice dishes work only with starchoice receivers.) There will be many wires coming from the satellite dishes.

Splitting board:

The incoming wires from the Satellite dish(es) are brought to a splitting board, which has splitters mounted on it, in order to take the signal(s) from the satellite dish and split the signal(s) into additional signal(s).

Affix a heavy sheet of plywood in the headend room or wiring closet, near where the satellite wires come in. Be sure that there is plenty of room near this board for the racks which will hold the other pieces of the system. Individual splitters are then NEATLY screwed to the splitting board, labelled, and the wires strung as neatly as possible.

Receivers:

Each of the wires from the splitting board will come to one individual receiver, such as the three shown at the left. These receivers decode the signals which come from the dishes. The signal is then sent out of the receiver as an audio-video signal.

Many kinds of receivers are available, and come in both commercial and residential grades. Some receivers are more "agile" than others, meaning that they are able to receive a greater range of signals. Receivers come in both mono and stereo versions, with stereo receivers generally being more expensive. Before choosing a receiver, like all "head end" technology, research all of the available options first, and make the choice based on both product suitability and cost.

Modulators:

Each of the wires coming from a receiver will come into a modulator. The modulator takes the audio-video signal from the receiver, and slots the signal into a specific RF frequency spot. Modulators allow for control of the RF levels of the carrier wave on the on the RF signal, and audio levels.

Outgoing Combining System:

All of the wires from all modulators come to one outgoing combining system, which is used to send all of the RF signals through one coaxial cable, to the end users, via the cable plant. The combining system basically "stacks" all of the signals into specific frequency slots, and sends them into one cable.

Launch Amplifier:

This is the last piece of equipment that the signal goes through before it leaves the head end. It is commonly
referred to as the "launch amp", mostly because of it's position in the plant. All amplifiers "launch" the signal though, so when purchasing an launch amplifier, the
amplifier you are buying may not specifically be called a "launch amp."

Some of the "launch" technologies in a cable plant head end include: Fiber optics (laser), RF wireless, and RF coax (sometimes also known as "contained signal"). All will have required incoming signal level constraints and pre-determined gain factors (amount of amplification in Db). Ask product salespeople or suppliers, as they are very knowledgeable and can help make decisions based upon the needs of the cable plant.

When the combined signal comes to the launch amp it will usually have a slope factor of 0 Db. This means that all of the modulators are outputting audio and video signals in their individual frequency slots at the same Db level. The launch amp then adds "gain" to those levels - similar to "turning up the volume."

Because lower frequency channels will travel farther than higher frequency channels set at the same decibel level, the level needs to be turned up higher on the higher frequency channels. This creates a difference in decibel level, or "slope" between the levels of the lower and higher channels.

In graph form, each channel would show a higher decibel level than the preceeding channel. The decibel level between channels is not significant since a cable plant running 80 channels would show a maximum slope of about 12 decibels (dB). However, slope is critical as the next amplifier in the cable system is dependent on a "flat" incoming signal level in order to start the
re-amplification process with the least amount of distortion.

All amplifiers have the capability to control gain and slope to some degree. They can also provide the technician with additional control as most amplifiers provide interchangeable equalizers (with different values) for further slope control and "pads" which help to control gain levels more accurately within the amplifiers themselves. This is very important, because If proper levels are not achieved within a cable plant, it will not function!!

Signal max/min decibel requirements and levels will be provided by any and all product suppliers. All attenuation losses of frequencies are constants which are also worsened with larger cable size and when additional "inline" equipment is added. Suppliers will provide
this information specifically for their products. Once the equipment has been purchased, it is simply a matter of mathematics that will decide what levels are used and where the equipment is installed in the line.

The next portion of coaxial cable installation deals with cable plant installation, particularily connectorization.