BP Srivastava , Senior Advisor , BECIL

Preamble

At a time when digitization of radio transmissions is in the air and priorities for doing so are being worked out, it seems necessary to iterate that radio continues to hold its primacy over other mediums in the country not only because 72.2 percent of India lives in its nearly 641,000 villages but also because of its ease of listening in both static and dynamic conditions besides its economics of reception and cost-effective production of content.  Radio has also demolished the rural urban divide about its acceptability, with boom in listenership caused by car radios because of the ever increasing time taken in transportation from one place to the other. Radio is, therefore, the medium for the affluent as well as for the common man, like the tiller of the soil, the person who canes the chair, or the shoe shine boy sitting on the road side. Radio is thus the medium for the masses of India. However radio, in its present analogue form has now started facing challenges from other forms of dissemination of information and entertainment. It is therefore becoming necessary for the analogue radio to give way to digital transmissions to enable broadcasters to bring novelty and variety to their programs with the availability of more channels and new technical features for providing added information to their listeners. A thought is, however, required to be given, while setting up the priorities, to the propagation characteristics of various modes of broadcasting namely medium wave (MW), short wave (SW), and VHF/ frequency modulation (FM) and their suitability for different services such as national, regional/sub-regional, local/city, and sub-local/community services required for the country.

The need of the hour, therefore, is to set up priorities of digitization in such a manner so as to meet the twin objective of changeover from analogue to digital as fast as possible and at the same time fulfilling the needs of different services keeping in view special conditions of our country such as its spread, terrain, population, languages, dialects along with economic conditions of its people. In doing so, it is not necessary to be influenced by what has been done by some other country whose conditions may be different from those of ours.

Advantages of digital transmissions and choice of technology

There can be no two opinions about the advantages of digital radio transmissions in view of their characteristics of: 

  • Making efficient use of the spectrum by way of providing multiple channels on a single frequency
  • Transmitting additional amounts of information that radio is able to display 
  • Providing improved audio quality
  • Having less impact of noise and interference
  • Requirement of low receiver signal levels thus reducing transmission costs

Even though no final decision has been taken in respect of digital technology to be adopted by India, it is almost certain that the choice will fall on DRM because of its various features suited to the present state of radio broadcasting in India namely:

  • Ability of co-existence with the analogue services thus providing ease of migration from analogue to digital
  • Compliance with existing spectrum masks and analogue frequency grids related to the entire spectrum available to sound broadcasting 
  • Compatibility of being used in amplitude Modulation (AM) as well as FM
  • Providing near-FM quality signal on MW and SW

It is because of these advantages, especially those associated with AM, which has been the backbone of domestic broadcasting in India, that All India Radio has already started using this technology in some of its MW and SW broadcasts.

Modes of radio broadcasting, their characteristics, and their use in India

Domestic broadcasting in India is being carried out onMW, SW – both belonging to the family of AM and VHF/FM, having been introduced in the country at a much later date than in other countries of the world. MW has been the principal mode of domestic broadcasting all over the world, and specially in India, because of its ability of providing wide area/long distance coverage with its propagation characteristics of day-night ground wave coverage and extended night time coverage by sky wave,  before it was displaced from its exalted position by FM.  For example, an area equivalent to that of a  circle of 400 km diameter can be covered with a 50 kW MW analogue transmitter (with much less power in the case of digital transmission) operating at a medium frequency of 1000 kHz in a region of medium soil conductivity of 20 MS/m. 

As far as SW is concerned, it has generally been used by most of the countries for their external services because of its propagation characteristics of providing long-range sky wave single hop or double hop coverage.  In India, however, it has profitably been used for domestic c broadcasting also, not only for the purposes of all India relay of news bulletins prior to the satellite era but also as a backup for MW services in every state taking advantage of tropical broadcasting dispensation to India in 120 m, 90 m and 60 m bands. Such a dispensation is made to the countries situated in tropical regions taking into consideration the fact that SW is somewhat less prone to interference from thunderstorms than MW radio. In addition, SW has also proved very helpful in covering the country when India did not have so many MW transmitters to reach every nook and corner of the country. A classic example of a highly acceptable use of SW has been the broadcast of Binaca Geetmala from Radio Ceylon covering almost all of India taking advantage of its geographic location vis-à-vis India using H/4/4 antennae giving a beam width of 26 degrees. Even today the National Channel of All India Radio is being broadcast from two SW transmitters along with three MW transmitters providing 100 percent coverage to 16 Indian states and 50 percent and more coverage to four states. 

India has thus made good use of a mix of modes to cater to its broadcasting needs and would do well continuing to do so in view of the improvement in quality of reception that DRM will bring to MW and SW broadcasts. 

Various types of broadcast services to be catered to 

Radio broadcasting all over the world and not only in India is not a single tier service that can be catered to by a single mode of transmission, since needs of different services are different and so their catchment areas. India’s has traditionally been a three-tier broadcasting service namely national, regional, and local service. With the opening up of the radio broadcasting sector, many more layers have been added to the earlier three tiers in the form of sub-regional, city-centric, community, and educational services. This has given rise to multiplicity of categories of broadcasters namely government broadcasting, public broadcasting, private commercial broadcasting, community radio broadcasting, educational broadcasting, and any other public service broadcasting. A single mode of radio broadcasting can, therefore, not cater to all the program services. With the prospects of getting near FM quality sound on MW and SW by DRM, with the added advantage of robust signal lesser prone to fading, noise and interference, both MW and SW can profitably be used for coverage requirements of national and regional services while FM may be used for local coverages of various types.   It is in this context that this writer does not agree with the findings of IIT Bombay, the agency that has carried out an audit of Prasar Bharati services, to banish MW services except for hilly and mountainous regions and put all the eggs in the basket of FM.

Creation of demand for DRM receivers to bring their costs down 

It is a well-known axiom that cost of any commodity is inversely proportional to the volume of demand.  So is the case with radio receivers where content is the king. As such cost of a DRM receiver is not expected to come down till an alternate attractive program, other than what is available on simulcast mode, is available to listeners. In this connection, que is to be taken from the miracle done for the cost of FM receivers by the introduction of private FM broadcasting, even though FM had been in operation in the country with All India Radio for about 10 years. The need of the hour, therefore, is to create a new regime on FM, distinct from the present private FM, that is most likely to go on simulcast mode. The proposed new regime should provide attractive alternate programs to catch the imagination of radio users. As far as MW is concerned, thought may have to be given toward inviting private participation in All India Radio by providing time slots and allotting new channels that will accrue on AIR transmitters as a result of digitization so as to increase listenership.  

Proposed priorities for digitization

As brought out above, digitization is going to result in improved performance of all the modes of radio transmission. The advantages that this is going to bring to the AM mode in terms of quality of received sound and reception far outweigh those accruing to FM, where the major gain is going to be in availability of more channels. Considering the present state of radio broadcasting in the country, it is proposed that digitization of MW and SW services should get priority over FM. All India Radio has already taken a lead in this direction by setting up 35 MW and 2 SW transmitters with DRM capability.

Proposed line of action 

The line of action proposed for various modes is given in the following sub-paragraphs.

Medium wave

Digitization should be continued by All India Radio on all their transmitters working for national, regional, and sub-regional services with a thought to be given toward inviting private participation in them, made possible with digitization. As far as local service is concerned, a mix of digitized MW and FM may be employed as may be found necessary from a technical point of view.

Short wave   

There seems to be an immediate need to restore state wise SW services of All India Radio with digital transmissions.

VHF/FM

 Digitization of private FM is already under consideration of the government and changes in private FM phase-III policy are being contemplated. However, seeing the period of licenses of the licensee broadcasters, digitization is likely to go on simulcast mode which is not going to help the cause of increasing the demand of DRM receivers and thus bringing down the cost of receivers.  An entirely new digital regime with alternate attractive programs is, therefore, the need of the hour. Such a regime is proposed to be initially set up in 14 large cities of the country with a population of more than 20 lakh with suitable incentives in their license conditions to promote digitization.

Frequency separation of new regime channels from the existing ones

Since the channels under this regime are to work side-by-side with channels operating under the present regime, the transmitters for these new channels will have to be set up at new locations as the towers at the present sites have no slot available for their antennae. For this purpose, studies of DRM-related protection ratios, especially between DRM and analogue FM, have been carried out to determine the frequency separation of the new channels from the present ones to obviate the necessity of co-location. Studies have shown that a frequency separation of 400 kHz will do the needful. As such it is proposed that frequencies 400 kHz apart from the existing ones may be allocated to the new regime channels in each of these 14 cities.

Way forward

Digitization of transmissions is the future of radio broadcasting. Its success will, however, depend upon the availability of attractive alternate programs on digital platforms. Digitization is as much required for AM services as for FM. Priorities are therefore required to be set up keeping in view the requirements of various types of services and special requirements of the country in terms of its size, population, languages, dialects, and also the economic condition of its people.