In-house cable TV systems are found in hotels, stadiums, schools, businesses, hospitals, senior living residences, homeowner associations, prisons, ships and other facilities where a large number of TVs receive the same set of TV channels. Most in-house cable TV systems are a replica or subset of standard commercial cable or satellite TV offerings; but for many facilities there is a need to add private community channels. For example, a residential building might create a channel for a weekly activities schedule, a hotel might need a resort channel to highlight amenities and restaurants within the hotel, or a prison might need a comfort channel with specially curated content. Whatever your application, if you’re looking to add a local TV channel to your in-house channel line-up this article will help guide you to a solution.
The first step in adding a channel is understanding what type of in-house cable TV system you have. To explain the basic concepts, the image below shows the basic components of a cable TV system and the principles behind it. In this example we show how you can create your own two channel cable TV network using common AV components. This happens to be an analog system, but the RF network principles apply to digital channels as well
Obviously this is a simplified view of a TV network. Those who are very familiar with TV technology may find some of these descriptions simplistic. Our intention is to explain a level of detail necessary to understand the basic operation of a digital TV network.
Chapter 1: The Anatomy of Digital In-House Cable TV
In a digital TV system many of the analog headend building blocks still exist, but they are implemented using digital technology rather than analog. Below is an example of a private digital TV headend.
Below we have identified a few key digital TV (DTV) components and terms that will be referenced in this and future chapters of this document.
|Linear TV||Traditional television channels that provide continuous programming without any time-shifting or on-demand content selection. I.e. Broadcast TV.|
|On-Demand TV||Digital TV programming that allows the viewer to select a program from a menu and watch that program at any time. TV of this type provides features such as pause, fast forward, etc.|
|IPTV||Linear or On-Demand TV distributed over internet protocols rather than traditional cable TV protocols.|
|Headend||A collection of AV equipment that creates one or more TV channels for distribution over the TV network.|
|Encoder||A device in the headend that encodes audio and video so that it can be transmitted as a stream of bits over a digital network.|
|Multiplexer||The portion of the headend that combines one or more encoded AV streams into a single multi-program stream and assigns channel numbers such as 28.1, 28.2, etc.|
|Modulator||A device located in the cable TV headend that electrically formats the multiplexed TV channels for distribution as radio frequency (RF) signals over coax wiring.|
|Upconverter||The portion of a headend that applies the modulated RF to a particular carrier frequency in the cable TV RF lineup.|
|Amplifier||A device which increases the signal strength of the modulated RF so that it can be transmitted over longer distances of coax wiring or through coax wiring splitters which allow the signal to reach multiple receivers.|
|Coax Wiring||An impedance controlled wire, circular in shape, that protects the modulated RF signal being transmitted from the headend to receivers.|
|RF Combiner||A passive device which joins two coax wires into one by combining their respective RF signals without introducing external RF interference. It is used to combine the output of two headends or RF outputs within a headend.|
|RF Splitter||A passive device which replicates the RF signals on a coax wire onto two or more coax wires without introducing external RF interference. It is used to feed multiple receivers. Splitters can be chained together to increase the number of receivers supported.|
|Load Balancing||Designing, testing, and adjusting an RF network to create a balance where each receiver has the same signal strength for each channel in the coax wire. The most common issue being the number of splitters is each leg of the splitter tree is uneven from the perspective of the receivers.|
|DTV Receiver||Also referred to as a set to box, cable box, receivers, DTV tuner, etc. May be provided by the cable operator, purchased from a third party, or embedded into a modern digital TV.|
|Tuner||The portion of a receiver that separates the requested portion RF carrier from unwanted noise.|
|Demodulator||The portion of a receiver that decodes the tuned RF into a bit stream (DTV) that can then be decoded by a processor and eventually turned into one or more audio/video (AV) streams presented on the TV screen.|
|Decoder||The portion of a Digital TeleVision (DTV) receiver that decodes the audio and video found in a portion of the AV stream. The decoded video is rendered on the TV screen or passed to the TV via HDMI or another digital connection.|
Most, if not all, of the DTV building blocks can be found in every digital cable TV system. In some cases, such as consumer cable TV, the headend is located many miles away and the distribution network is large. In other cases, such as a hotel’s private cable TV network, the headend and distribution network are both on the hotel property. Recognizing what type of infrastructure you have is the first step toward installing private cable TV channels on your cable TV network.
While there are similarities between cable TV installations, each one is a little different. In the next chapter we will discuss how to understand what technology is used in your in-house cable TV system.