Specifying an IRS for Housing

An IRS (Integrated Reception System) is the system which distributes TV and Satellite RF signals from a single array of Aerials and satellite dishes to a complete development of apartments or houses.

This Blog highlights some of the key areas to consider when specifying an IRS.

With the development of new technology and specifically the use of fibre for distributing TV/Satellite signals, there is the potential to design and build a flexible IRS which will cater for most residents requirements. However in practice, consultants are seldom aware of the possibilities and specify systems which are just not flexible enough to satisfy the evolving requirements of residents.

Common Problems with Specification

As a company who designs and builds TV distribution systems, we get to see a variety of TV specifications. Unfortunately, many are poor, which ultimately results in the building of unsuitable systems and users/residents not receiving the services they require. Common problems with specification are:

Specification of out dated technology. For example the master/slave outlet scheme described below.
Unnecessary design information. When designing an IRS, the designer only needs to know what it does. Detailed schematics showing equipment and cabling are unnecessary.
Too many standards. Many specs are copy and paste lists of relevant TV standards, many of which are out of date. Insufficient information. See ‘So What Should a Specification Include’ below for what is required.
Inconsistent information. If the written spec, TV schematic and room drawings disagree, it can cause chaos during the tendering process.
Insufficiently Flexible. An IRS will be expected to be used for at least 10-15 years. However, it is almost impossible to add apartment feeds or satellites later. It is therefore important to include sufficient feature or flexibility in the initial specification.

Coax or Fibre Distribution?

An important question to answer at the specification stage is whether we require a traditional coax system or a fibre based system (known as a Fibre IRS or FIRS). In a traditional coax system, RF amplifiers and multi-switches will be installed in the risers, feeding signals to the apartments via coax cables. So all of the equipment is shared. However, in a FIRS the signals will be distributed over a passive fibre network and only within the dwelling are the signals converted back to coax. So apart from the headend, most of the equipment in a FIRS is located within the apartments.

A FIRS provides a number of advantages:

There is therefore no restriction on the number of satellite outlets in the apartment.

There is far less equipment and cables in the risers.

A FIRS is more reliable and maintainable. The only active equipment is at the headend and in the dwellings.

Note that most medium/large IRS’s are now designed with fibre backbones. This is the most cost effective and efficient implementation. However the system is only classified as a FIRS if the fibre is extended into the apartments.

Apartment Layout – Master/Slave or Direct?

In the master/slave arrangement, a Sky+ outlet is provided in the living room (the Master), which feeds Slave TV outlets in other rooms through an adjacent Return outlet. The return outlet is typically connected to a TV amplifier or loft box in the utility cupboard the outputs of which are connected to the Slave outlets. There are a number of drawbacks with this scheme:

It was designed for the situation where a Sky Box could be viewed in another room using the return cable and a Magic Eye device. However, new Sky boxes don’t have a return output (although it is possible to purchase a separate adapter) and the return use an old analogue signal which many new TV sets cannot receive and certainly doesn’t provide HD.
In practice, residents often pull out and lose the cable joining the master outlet to the return. Then, possibly years later, they are puzzled when they they plug a TV into a slave outlet and get no signal.
Many residents will require Sky+ and other satellite signals in other rooms.
The utility cupboard TV amplifier consumes power, even when not used. And it often fails.

With the Direct scheme, all outlets are fed either directly from either the riser (coax distribution) or from the utility cupboard multi-switch (FIRS). Usually two feeds or cables per outlet. It has the advantage that satellite receivers can be used in any room. Also it is less confusing for the resident – all outlets provide signals with no return connections to worry about. We strongly recommend the Direct layout for new installations.

So What Should a Specification Include?

The information that is required is very simple and can normally be summarised in a few paragraphs:

Coax or FIRS Distribution. A FIRS system will normally work out more expensive than a Coax. So if this is not specified, the installer will normally install a Coax system.
Location of rigs. Ideally just one set of Aerials and Satellite dishes is required. However, where the development involves independent buildings with limited underground links, it may be more practical to specify separate rigs.
How many satellites? As a minimum, the installation should provide TV, DABS/FM Radio and Astra 28.2E Satellite (Sky and Freesat). However, depending on the profile of expected residents, more satellites can also be specified. The second satellite would normally be Hotbird and the maximum practical number of satellites is normal four. However, see the Flexible FIRS described below – an excellent choice for high end housing. As a guideline, the cost uplift for 2, 3 and 4 satellites is 10%, 23% and 25% respectively. This uplift can be reduced by restricting the full range of satellites to certain apartments.
Apartment Layout. Direct or Master/Slave? Which rooms require outlets? As a guideline, at least the living room and each bedroom will require a dual feed (or Sky+) outlet. Additional rooms, such as the kitchen may also benefit from an outlet.
Number of feeds to each apartment (Coax Distribution System only). This number will often be dictated by the dwelling layout and may vary according to the dwelling size and type.

The Flexible IRS

The fibre technology for distributing TV and Satellite offers powerful options beyond a traditional IRS. An example of such a system is the Able Flexible FIRS. Aimed at medium to high end housing, this uses fibre technology to offer 12 or even more satellites. As standard, all users receive Sky and Hotbird. However, they can can also be connected to two more satellites selected from the full range. The Flexible FIRS will typically costs just 50% more to build than a basic single satellite system.

Note: The relative costs are based on a large IRS (100+ dwellings) with Direct Dual TV outlets in all habitable rooms. They also exclude the dwelling cabling, which if included would reduce the relative differences.