FM DAB Transmitter

How to start a DAB radio station

Starting a DAB multiplex for Small Scale DAB

As a broadcaster, the easiest and lowest cost route to broadcasting on DAB can be to simply lease space on a multiplex, either on an existing service - if available, and where capacity permits - or a new local multiplex, if one is launched as part of forthcoming local DAB licensing. However, for the rest of this article, we’ll assume that you wish to create and run a local multiplex.

A multiplex owner will:

The UK regulator recently trialled small-scale DAB multiplexes in various parts of the UK using lower cost open-source processes now available.

Whilst software to achieve encoding, multiplexing and modulation stages of DAB transmissions are now in the public domain, configuring such software to run on proprietary Linux computer platforms is extremely complex and not for the feint hearted. In any case, some critical open-source aspects which can aid system reliability and increase efficiency are yet to be developed.

Experience has recently shown that, while cost savings can be made for the multiplexing stage, transmitting is best performed by professional hardware based broadcast modulators and amplifiers, especially in the interests of preventing the prohibitive ongoing running costs associated with inefficient RF implementations. Also recently proven is the narrow margin of cost-saving achieved by attempting to use open-source software defined implementations for the RF modulation stage.

Unlike FM, a DAB transmitter broadcasts a 'bundle' of digital carriers across a widespread frequency, containing the digital audio for several stations plus the associated data and error correction information. In very loose terms, a 200W DAB transmitter is like a 2kW FM transmitter, due to the widespread carriers and peak powers involved. The linear RF power amplifiers are far more complex those used in FM broadcasting. They also take a lot more power (electricity) but, because several stations are broadcast by one transmitter, running costs and spectrum use are actually more efficient than FM. With careful planning and network design, transmitter operators can keep both the initial equipment costs and ongoing costs down by using antennas with gain to create the effective radiated power required. Importantly, transmitter locations need to be carefully chosen so that directional coverage will include all target areas.

In short, it seems that the main cost-saving over traditional DAB broadcasting can only, in reality, be achieved at the audio encoding and multiplexing stages. With in-depth Linux computing knowledge and expertise in DAB multiplex technical parameters, a small scale operator can set up their own multiplexing system. They will also need to manage and maintain it, configuring technical parameters for each service, as part of on-going operational changes.

There are many ways in which a multiplex can be realised. Some are shown below, and can use any combination.

Small Scale DAB
Figure 1. Typical SSDAB installation. One station shown, others would also address their CODEC to the multiplexer over the IP network
Start a DAB radio station
Figure 2. As above, but with contributors linked by STL to central encoding and multiplexing
DAB transmitter for SSDAB
Figure 3. All broadcasters co-located with the transmitter

If a new multiplex operator feels able to do this, plus set up their own methods of programme delivery networks for each network, the only additional items required would be a transmitter, filter and antenna. For those who prefer to have this part planned, installed, configured and maintained (often remotely, by connected experts) we can offer ongoing service plans.

Before attempting to address equipment costs, we suggest that you create a business model;

Only when armed with this information will it be possible to begin ascertaining the likely capital costs of the RF transmission equipment required. When you have this information, please do contact us so that we can assist with pricing, but please also bear in mind that the UK regulator has yet to decide the technical transmission parameters for licenses.

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