European Stars and Stripes (Newspaper) - August 4, 1990, Darmstadt, Hesse                                Technological leap to a a saw Quot a a Van a to j l 1 la a i 1 \ j by Andrew Pollack new York times r Adio broadcasting is preparing for its biggest technological leap since pm technology was developed in the 1940s and 50s,. A a. A the leap will be to digital broadcasting in which music and information will be sent As a series of zeros and ones As in computer code. Such digital broadcasts would have the same High Quality of sound a free of Static and Hiss a As the digital compact disks now replacing analog phonograph records any such replacement of the analog systems used in current am and pm broadcasting in which the music is represented As continuous electromagnetic Waves that mimic the musical sound wave is not Likely to begin until late in this decade. But technological and political activities Are already heating up. A consortium of european broadcasters stereo equipment manufacturers and research institutions has already developed and demonstrated a sophisticated. System for what it Calls digital audio broadcasting from a combination of satellites and land based towers. In the United states three companies Are. Introducing services this year in which digital music will be transmitted 1o Homes Over Cable television lines three other companies have applied to the Federal communications commission for frequencies to begin satellite transmission of digital music to Home and car radios in a few years. And the government is exploring the idea of creating a worldwide digital satellite service the transition to digital radio is Likely to be Long and controversial however. A a this is radio s a div Quot said John Dabel executive a vice president of the National association of. Broadcasters. He was referring to the Many issues being raised by digital radio that Are strikingly close to those surrounding. High definition television which would provide sharper pictures than existing service. The issues include How to make the transition without instantly making obsolete the 500 million radios in the United states. There will be questions about which Standard to use for digital radio. Will the world adopt a single Standard like the european system making possible worldwide. Broadcasts or As with High  television will the United states Europe and Japan develop separate systems to help their own industries in the United states a political Battle for control of the new digital radio has already begun the National association of broadcasters representing radio broadcasters passed a Resolution this year opposing the introduction of  services from satellites saying the services should be provided from land based towers. Industry experts say tie broadcasters Are concerned about potential Competition from digital  satellites which would probably be offered by other companies rut if some broadcasters tear Competition lion digital Rad a others View Ilas something that the broadcasters must embrace. Otherwise they say Raffio will not to competitive in sound Quality with digital compact disks digital tapes and the digital Cable music services. Even when radio stations play compact disks on the air much of the Quality is lest in Trie am or f m transmission compact disks can reproduce frequencies up to 20,000 cycles a second White f m radio can reproduce1 frequencies Only up to 15.000 cycles a second moaning that some High pitched sounds Are lost. And the dynamic Range Trie dime Enoe Between the loudest and softest sounds is More than 90 decibels Tot compact disks but less than 70 decibels for pm radio. Am radio is even More  music systems like compact disks represent music As a series of numbers. To make music for a compact disk for instance the music is sampled 44,100 times a second and the sound level at each instant is represented by a number written. As a string of zeros and ones. Such digitization has some great advantages in eliminating noise during the recording process or during transmission. A digital radio station would need far less Power for its signal to be understood by the receiver above the noise. A digital radio station transmitting with a Power of Only 1,000 Watts with a Power Bill of $15 a month would be Able to cover the same area As an pm station transmitting at 50,000 Watts with a Power Bill of $6,000 a month. The major drawback of digital transmission has been that it requires a lot of space on the radio frequency spectrum and such space is in Short Supply a compact disk with 44,100 samples a second. Represents each Sample by a 16-digit string of ones and zeros. There arc two such signals for each stereo Channel for a total of about 1.4 million zeros and ones that have to be transmitted each second Michael Drew the Washington Post that would require a Swath of frequencies several times wider than that required for an pm station. The key to making digital radio feasible is data compression which eliminates redundant information s that fewer bits have to be transmitted at the receiver the full information can be reconstructed. One technique is to Send Only the difference from oni sound Sample to the next. If three successive sound Levels Are say 1002, 1003 and 1005, then instead of transmitting the full numbers the system can transmit the first number and then merely a 1 and a 2. The european system takes advantage of the fact the some sounds cannot be heard because they Are Loo close in frequency to other sounds that Are louder a phenomenon known As psycho acoustic  by eliminating such sounds the european project a  number of bits by More than a Factor of six no system for satellite or Over the air digital audio broadcasting is Likely to get started until after 1992, that is when the world administrative radio conference is scheduled to consider setting aside frequencies. In the meantime three companies in the United state Are beginning digital music services on Cable television a w Ich does not have the same limitations on frequencies away with the ghosts Page 16 the stars and stripes a european consortium developing a system for digital radio broadcasting has come up with a solution for a problem that causes interference in pm radio broadcasts. The problem arises when the radio signal Roaches the receiver Over More than one path at slightly different times. A radio wave that bounces Oft a building might reach the receiver a fraction of a second after the signal that comes directly from the broadcast lower causing an Echo. The same phenomenon is responsible for Quot ghosts Quot in television reception if the reflected signal is exactly 180 degrees Cut of phase with the direct signal the radio reception will be cancelled out entirely. That is the cause of the familiar phenomenon particularly when driving in Urban areas in which reception seems to be lost in certain locations saturday August 4, 1990 returns0 of a 3 new Post on reception the european system for eliminating the problem Novin As Multi path reception is called coded conf Romh Quot req Jenev do vision multiplexing and is As complicated As it sounds. In existing am and pm broadcasting each station is a a frequency its own narrow Road so to slum system up to 16 stations would 1 Ord r Uri in d 0f free Kjono est in essence a wide Road with Many lanes. 5 so 3nal 1s broken info pieces and sent. J of ,u1�?~ ret to Ien cies different fanes of the Road on rhe Radi 0 receiver is intelligent  m re up thu  stat on and of construct to original  new York times