Radio has always been a magnet of creative brains. There are lists of things to be considered while setting up a radio station. The technical infrastructure for a FM station requires expertise in broadcast and audio engineering. The FM network infrastructure is considered to provide efficient and solid support for the vigorous delivery of time critical, life-saving messages.

Broadcast expertise will be required for setting-up a reliable and rugged network, while audio engineering expertise is required for aspects related to station sound and to ensure excellent quality reception.

First step will be to finalize the design of the station, with reference to the number of studios, operations and programming features to be incorporated such as transmitter configurations, antenna and tower design as per coverage requirements. The facility branding is required to be in place at the start as it drives inspiration for a creative mind.

Post-design finalization, the BOQ for each of the equipment is finalised and vendor offers invited. Techno commercial offer of vendors should be evaluated by cross-functional team of technical, finance and commercial authorities.

Primary and important factors that are considered while evaluating and finalisation of equipment are as follows:

• Technical specifications
• Reliability of equipment
• Features and USP
• Support set-up of vendor
• Feedback of performance from technical experts.

FM infrastructure can be categorised into four areas:

• Studio infrastructure
• Play-out software and systems
• Broadcast infrastructure
• Antenna and tower infrastructure

I. Studio Infrastructure

Typical FM studio set-up has on-air studio used for live broadcasts and is the main studio. There is also a back-up studio that has the same setup as the on-air studio and will be used in case of faults in on-air set-up. In addition, there are a couple of production studios, which will be used for recordings, editing, mixing and for production work.

Studio equipment used in professional state-of-the-art studios are:

Broadcast consoles (mixers): These are the heart of the FM station operations. Various input and output audio channels are routed through this console, which have a modular design, gain controls and audio-level meters for monitoring. Standard broadcast consoles come with 10-12 input faders and four output buses.

Professional broadcast microphones: High performance broadcast microphones with excellent resolution and depth for vocals are used in studios. Flat frequency response and selectable filters option are other features of quality microphones.

Digital voice processors: Voice processor is a programmable microphone processor that is flexible, powerful and easy to use. Popular units have two microphone channels that can be processed simultaneously. These offer comprehensive set of voice enhancement tools. Settings can be saved as presets for later recall.

Professional CD players: Used for play-out and recordings. Professional models will include balanced analog and digital outputs. Plays with auto ready and auto cue features and plays out commercial CDs and MP3 disc as well.

Telephone hybrid: Used for listener's phone call-ins. Telephone hybrids are digital equipments, which perform hybrid functions, gain control and filtering. Regardless of telephone line characteristics, telephone hybrids provide superior performance.

Digital audio router: Audio routers are high performance microprocessors based audio switching system for broadcast facilities. Central switching system provides flexibility of routing audio channels between studios as per requirement. Remote modules of routers are used for interconnecting multiple studios.

Monitors (speakers): Active two way studio monitor speakers for near field monitoring is used in broadcast studios.

In-production studio recording, editing and mixing is carried out using professional equipment by the sound editor. Final audio elements are produced by sound editing software.

Main criterias by which we need to evaluate studio equipment selection are robust digital circuits having features like gain control, modular design, user-friendly operations.

II. Radio Automation Software

Radio automation software is required for scheduling and for play out of audio elements. Radio software is capable of scheduling and play-out of various audio elements (songs, commercials and linker elements). Automation software is interfaced with broadcast mixers and high end professional sound cards are used for play-out systems.

Automation software should have the facility for an RJ to pre-record the show. Also facilities like remote scheduling of music and voice tracking from remote locations should be in-built in the software.

Main aspects for evaluation of Radio Automation Software is reliable architecture, auto back-up functions, user friendly operations, easily up-gradable versions for future requirements and remote support.

IT infrastructure includes network of servers, work stations and PCs for Radio Automation Software. Office network has domain controller with user PCs connected. IT security, Data backups and archiving are important tasks which IT department handles.

III. Broadcast Infrastructure

Studio to Transmitter Link (STL)

Generally, studios and transmitters are in two different locations. Studio output is connected to transmitter site by Studio to Transmitter Link (STL). For good quality uncompressed audio re-generation at transmitter site, STL codecs with linear coding techniques is preferred. Each station will have minimum of two STL links for redundancy purpose. Most popular and reliable STL links are point-to-point leased lines, managed IP networks, microwave/RF link, VSAT or ISDN connections. These links are designed for 100 percent uptime. Based on feasibility study at studio and transmitter locations, primary and secondary links are installed.

In addition to the above links, using cost-effective ISDN connection for studio to transmitter connection as third STL link is recommended.

It is also recommended to have a combination of wired and wireless STL links for every station to ensure fool proof STL links.

Audio Processors

Audio processors are crucial equipment in FM chain. Usually, audio processor is installed in transmitter location, but it can also be installed at studio location if required. Audio processors settings will determine the station sound to a large extent. Excellent station sound can be achieved by setting various parameters of audio processor like low pass filter settings, high pass filter settings, AGC settings , Limiter settings etc. One can make station sound more powerful or increase loudness or sound output can be set on genre of music played using audio processors.

Transmitter

FM transmitter is equipped with:

• Exciter
• Power supply assemblies
• RF power amplifier modules
• One modular plug-in IPA
• Low pass filters and splitter assemblies
• Combiner assemblies
• Microprocessor controlled controller.

All the components are housed in a single chassis.

Exciter: Exciters are solid state wideband equipment providing continuously variable RF output at any frequency between 87.5MHz to 108 Mhz broadcast band in 10KHz increments. Exciter is equipped with digitally programmed frequency synthesiser, which generates and maintains the phase and frequency of carrier. A solid state RF amplifier provides amplification of the FM signal.

Power supply: Power supply section provides operating potentials for the transmitter power amplifier circuitry. Supply is equipped with overload protection, over voltage protection and high temperature protection.

RF power amplifier modules: Transmitter is equipped with power amplifier modules. Output of these modules will depend on each transmitter manufacturer design.

IPA module: Power from the exciter is amplified for application to the RF power amplifier modules by an IPA module. This module is identical to the RF power amplifier. Transmitter can be equipped with a second IPA module for redundancy.

Low pass filters and splitter assemblies: Low pass filters and splitter assemblies are installed before RF combiner units in transmitter.

Combiner assembly: Transmitter comes with auto-configurable combiner system. This unit matches the combiner to the number of operating modules in the transmitter. Unique features of combiner include very low loss, broadband and no cable connections. Typical combiner system consists of two 8 way combiner and one 2-way combiner.

Controller: Controller circuit board is equipped with microprocessor module. Controller board performs all system control operations such as on/off control, power trim, automatic power control and remote control interfacing. Also controller boards control the operation of all the controller front panel displays and switches.

Professional transmitter set-up is equipped with main and stand-by transmitter (low power transmitter) and monitoring rack. In case of main transmitter failure automatically transmission switches over to stand-by transmitter. Switching between the main and stand-by transmitter is carried out by transmitter main or alternate controller unit.

Transmitter's state-of-the-art design, redundant back-up systems and ease of operations needs to be evaluated while selecting transmitter. In addition, redundant exciter, IPA, hot swappable PA modules with robust power supply section should be part of standard transmitter configuration. Efficiency and effective heat transfer designs are other important factors, which we need to consider while selecting a transmitter. Transmitters should have excellent monitoring and fault diagnostic tools to monitor important parameters like voltages, currents, VSWR, internal temperatures etc.

Dummy load is equipment installed at transmitter site and is used for testing transmitters in ideal conditions. It protects the transmitter from getting damaged in case of fault in antenna and RF feeder cable.

Monitoring equipment used are FM modulation analysers, monitoring meters and tuners. Modulation analyser will measure average and peak modulation, left and right modulation peaks. Audio levels and quality of broadcast audio can be monitored by meters. Frequency of broadcast can be checked by PLL synthesised tuners installed in equipment rack.

Antenna and Tower Infrastructure

FM antennae can be broadly classified into directional and omni-directional antenna. Directional antennae are usually side mount dipole antennae and radiate in focussed direction, while omni-directional antennae are generally panel antennae, which are installed on all four bays of tower and radiate in all directions. Most important parameters of antenna are gain of antenna, polarization and directivity of the antenna. Depending on regulations, antenna gain and design is finalised and also height of tower is determined by coverage area required and regulations if any.

Above details clearly emphasise that each of network elements in FM broadcast network chain contributes to Sound of station and hence while setting-up FM station the best of class equipments have to be installed, be it studio equipment, STL equipment, IT and automation software, transmitter and antenna set-up.

To conclude, setting-up a world class FM station is a blend of science and art. Technology is science along with sound expertise which is an art and is essential for achieving the ultimate listener experience.