DIGITAL RADIO GUIDE

TERRESTRIAL TRANSMISSION SYSTEMS - DRM

4 Terrestrial Transmission Systems

This section provides a technical overview of the various digital radio systems available for terrestrial application: DRM, DAB, ISDB-TSB, and HD Radio. These systems operate in various frequency bands and offer different attributes and features.

4.1DRM – Digital Radio Mondiale

The DRM system encompasses a high level of flexibility in its design. These are noted in this subsection in the signal flow sequence going from the delivery from a program studio or network control centre to a transmission site and on to reception and decoding in a receiver.

4.1.1Key Features of the System Design for the Markets to be Served by the DRM System

The DRM system is a flexible digital sound broadcasting system for use in the terrestrial broadcasting bands below 30 MHz.

It is important to recognize that the consumer radio receiver of the near future will need to be capable of decoding any or all of several terrestrial transmissions; that is narrow-band digital (for <30 MHz RF), wider band digital (for >30 MHz RF), and analogue for the LF, MF, HF and VHF (including the FM) bands. In addition there is the possibility of satellite delivery reception in the L- and S-bands. The DRM system will be an important component within the receiver. It is unlikely that a consumer radio designed to receive terrestrial transmissions in the near future with a digital capability would exclude the analogue capability.

In the consumer radio receiver, the DRM system will provide the capability to receive digital radio (sound, program related data, other data, and still pictures) in all the broadcasting bands below 30 MHz. It can function in an independent manner, but, as stated above, will more likely be part of a more comprehensive receiver – much like the majority of today’s receivers that include AM and FM analogue reception capability.

The DRM system can be used in either 9 or 10 kHz channels, or multiples of these channel bandwidths. Differences on how much of the total available bit stream for these channels is used for audio, for error protection and correction, and for data transfer depend on the allocated band (LF, MF or HF) and on the intended use (for example, ground wave, short distance sky wave or long distance sky wave, with a data application service or without one). In other words, there are modal trade-offs available so that the system can match the needs of broadcasters worldwide.

As noted in more detail in subsequent parts of this subsection, the DRM system has the following structure. It employs advanced audio coding (AAC), supplemented by spectral band replication (SBR), as the main digital audio encoding. These are parts of the MPEG-4 audio standard. SBR significantly improves perceived audio quality so that the overall audio quality of a DRM signal is similar to that of FM (mono). Orthogonal Frequency Division Multiplexing (OFDM) and Quadrature Amplitude Modulation (QAM) are used for the channel coding and modulation, along with time interleaving and forward error correction (FEC). Pilot reference symbols are injected to permit a receiver to “equalize” the channel by comparing a known stored bit sequence with the corresponding received sequence of these special bits, and adjusting accordingly if there are differences in the received compared to the stored sequence.

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Grundig manual Terrestrial Transmission Systems, DRM Digital Radio Mondiale
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Digital Radio specifications

The Grundig Digital Radio represents a significant advancement in radio technology, combining aesthetics, functionality, and a user-friendly interface. As a pioneer in the audio and electronics industry, Grundig has successfully integrated modern digital capabilities into its traditional radio design, appealing to both nostalgic listeners and tech-savvy users.

One of the standout features of the Grundig Digital Radio is its versatility in reception. With DAB+ (Digital Audio Broadcasting) technology, users can enjoy a wide array of radio stations with superior sound quality, free from the hiss and interference commonly associated with analog broadcasts. The inclusion of FM and AM bands ensures that listeners are not limited, providing access to local stations that may not yet have transitioned to digital.

The Grundig Digital Radio is designed with ease of use in mind. Its intuitive interface, often featuring a clear LCD display, allows users to navigate through stations and settings effortlessly. Many models also include a built-in tuner that automatically scans and presets available stations, simplifying the setup process. For those who appreciate personalization, some variants come equipped with customizable presets, allowing users to save their favorite stations for quick access.

Portability is another key characteristic of the Grundig Digital Radio. Many models are lightweight and come with built-in handles, making them ideal for on-the-go listening, whether it's in the garden, on the beach, or during a picnic. Battery options, alongside mains power, ensure that users can take advantage of their radios wherever they choose.

In terms of sound quality, Grundig utilizes advanced audio technologies to deliver rich and clear sound. Enhanced bass responses and treble controls allow users to fine-tune their listening experience to match their preferences. Furthermore, many models feature additional inputs, such as AUX and USB ports, enabling users to connect their smartphones or other devices, expanding their audio options.

Other notable characteristics include built-in alarms and timers, which make the Grundig Digital Radio a versatile companion for daily routines. Some models even support Bluetooth connectivity, allowing for seamless streaming from a variety of devices.

In summary, the Grundig Digital Radio embodies the perfect blend of traditional radio appeal and modern digital technology, offering versatility, ease of use, superior sound quality, and portability to meet the diverse needs of today’s listeners. Its well-thought-out features and user-friendly design make it an excellent choice for anyone looking to enhance their audio experience.
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