At Aerial Services we’ve been installing and maintaining communal TV systems since the late 1960s.
Of course back then things were far simpler than they are today, there were only three analogue TV stations, there was no satellite and the Beatles were at number 1 with Hey Jude! Communal TV systems have evolved considerably since then both in how they work but also in terms of what’s actually available to the viewer.
Although there are some exceptions, such as in hotel systems, the vast majority of communal dwellings today receive their TV services using Integrated Reception Systems (IRS). IRS systems vary in their complexity but generally speaking they consist of a TV, FM and DAB aerial and a satellite dish. The signals are combined and then distributed to a number of individual dwellings to provide each resident with a wide range of services.
This is achieved by erecting aerials and dish(es) on the roof and running cables from them to a position in the building where we can install the distribution equipment which is collectively termed the “headend”. Because the headend is made up of electronic equipment this is normally situated inside in a tank room, riser or basement but it can also be fitted outside in a weatherproof cabinet.
The feeds from the antennae are amplified and filtered at the headend to ensure that they are robust enough to serve the amount of dwellings in the building. They are then connected to distribution units or “multiswitches” which combine the signals together so that TV, FM, DAB and satellite can all be fed down a single cable. Two twin screened CAI benchmarked coaxial cables are then run from the multiswitch to the TV point(s) in each dwelling and terminated in a Quad outlet plate which de-combines the signals for the resident to connect their equipment to.
The system outlined above is an example of a 5 wire IRS which provides digital terrestrial TV (Freeview), FM, digital radio (DAB) and Sky. However there is also a growing demand for satellites other than Sky to be included such as Hotbird, Astra, Arabsat and Nilesat. Each extra satellite requires an additional dish to be installed, four extra cables to be run to the headend, further amplification equipment and a different kind of multiswitch. So an IRS system with two satellites is referred to as a 9 wire, three satellites as a 13 wire and four as a 17 wire system. With the inclusion of extra satellites it is recommended to run additional cables to the TV points. It is possible to view multiple satellites from a single Quad socket but this means “looping” satellite receivers together which can cause “crashing”.
Fibre Optic IRS
Increasingly today fibre optic cabling is being integrated into the installation of IRS systems. Using Fibre within the TV industry is a relatively recent development although it has been used in the telecommunications industry since the 1980s. In 1997 the first fibre telephone cable of it’s kind which was called FLAG (fibre-optic around the globe) was laid on the sea bed between London and Tokyo.
There are numerous advantages of Fibre over traditional copper coax. Fibre can transport more information over far greater distances than copper. It is lighter and the cables have a far smaller diameter. Also because glass doesn’t conduct electricity there is no current flow so there are no earthing requirements. Fibre IRS systems work largely by using the same principles as traditional copper except that some of the components are different and that you can run the cables across distances of up to 10km.
A Fibre cable can be run right up to each dwelling which is then terminated in a Gateway Termination Unit (GTU). From a standard Quad GTU you can run up to four coax cables into each home or by using a Quattro GTU you can install a multiswitch with anything up to 32 outputs.