Cable Audio Services --- the (Hi-Fi) Sky's the Limit
Total Page:16
File Type:pdf, Size:1020Kb
CABLE AUDIO SERVICES --- THE (HI-FI) SKY'S THE LIMIT Ned Mountain UA-Columbia Cablevision, Inc San Angelo, Texas The time has come to re-examine the poten The development of aural entertainment service tial and impact of audio services within the can be looked at in a similar analogy. The same cable television industry. This paper com 3 forms of consumption exist; broadcast, cable, ments on several marketing and technical as and home audio recording/playback, but they evol pects of implementing quality service. A un ved in slightly different order. First to be de ique blend of technology, public demand for veloped was the phonograph in 1877. Next, com diversification, and new program services is mercial radio broadcasting began in 1920. These rapidly coming together that will allow crea two forms of audio entertainment make up the bulk tive operators to develop an exciting audio of today's available sources. Both industries product for their subscribers. continue to grow, flourish and compliment each other. The third item to be considered is audio services via cable. It is my opinion that the area is being left behind in our industries "blue INTRODUCTION sky" thinking. Cable television is a dynamic, expanding business with unlimited potential. Much cur TECHNICAL CONSIDERATIONS rent thinking is directed toward taking the It is possible to add a multi-channel FM audio "television" out of the term and looking at service in just about any well designed CATV sys the ultimate blue sky potential of the "ca tem provided that good engineering practices are ble". At this point in the growth of our in used. The spectrum from 88 to 108 MHz is gener dustry, it is a good idea to examine all po ally available for FM services with the FCC sub tential sources of revenue that·our broadband dividing this 20 MHz of spectrum into 100 chan networks will generate in the future. It is nels each of which is 200 Khz wide. Over the being demonstratr~d daily that the public's air channel assignments are never made on adja thirst for entertainment alternatives in the cent channels in the same area and the same should home is vast and underestimated. It is my be the rule when planning the cable FM spectrum. contention that the demand applies to audio If a minimum adjacent channel spacing of 400 Khz as well as video. is used, a maximum of 50 cable FM channel slots will be available. Local FM broadcast signals VIDEO AND AUDIO DEVELOPMENT should be translated to a new frequency prefer For the sake of comparison, let's look sep ably 400 Khz removed from the assigned off-air arately at the development of two types of e frequency. This is done to avoid multi-path pro lectronic home entertainment services; video blems and results in a clean feed of local FM and audio. Electronic video services started stations at predictable levels. A word of cau with commercial television in the early 1940's. tion: Be sure to use only FCC channel assignments Obviously, the needs of the public could not for cable FM as many of the new digital tuners be met with just one video channel; thus evol will tunc only these frequencies. It should be ved the networks, independents and public broad obvious that any serious FM service will require casters. Cable television came along early in the use of FM head-end processing so that level the life of broadcast video first as a means uniformity and control can be maintained by the to extend the broadcast range to new geographic cable operator. locations and in recent times, as we all know, to expand the programming varieties to beyond Speaking of levels, FM carriers can be run at those which could be broadcast in a particular a much lower level on the system, typically 15db area due to spectrum shortages. An additional below video carrier. The main reason is that the source of video entertainment service is rap only portion of the signal that is overly sensi idly emerging in the form of home video re tive to high carrier to noise ratio is the stereo cording and playback equipment. The concensus sub-carrier. Since this sub-carrier occupies seems to be that all 3 forms of video sources only 30 Khz of spectrum, the system noise present will continue to exist, compete, and to var in this slot is at least 20db lower than that pre ious extents compliment each other. sent in the 4 MHz video spectrum. The net effect 26 is that -15db levels will generally produce ster restrictions), satellite non-broadcast, and lo eo signal to noise ratios of 50db or greater. cal origination sources are combined in a pro gramming "blend" tailored for maximum acceptance The effect of adding even 50 FM carriers to a by our subscribers. system carrying 35 TV channels is insignificant. The net increase in amplifier level would be less If the same type of creative thinking were to than .2db. Since all FM carriers are at least 15 be channeled toward tailoring an audio service db down from video, resultant distortion products for our subscribers, what would the result be? will be insignificant and random. Essentially a well designed CATV distribution will be trans The first question I get asked when proposing parent to the FM signals and video operation will this concept is "Why Bother?? It isn't worth the not be affected. effort." Let's take a look at why aural service may well be worth the effort: Since FCC rules do not exist for cable FM, it is in the operator's best interests to define his 1. There are no rules or restrictions with own performance standards. The objective should regard to aural service. We are free to be to provide the subscribers with stereo signals develop these services with the sole ob free of whistles, beats and other noises. For jective of fulfilling subscribers desires. off-air sources, the commercially available hete rodyne processors will provide excellent quality. 2. No technical requirements exist for aural FM signals imported via microwave sub-carriers services. While the majority of such ser (be it terrestrial or satellite), however, deserve vices will employ standard FH broadcast special attention. A general rule of thumb would and multiplexing techniques, the door is be that if the microwave system is single hop or wide open for technical innovation. multi-hop with no demod - mod process at interme diate points, than standard heterodyne processing 3. The radio broadcast industry is healthy! with 75 Khz deviation will probably provide ex As of April 1980 there were 8748 radio cellent results. If the signal must go through stations on the air in the United States.(2) more than one demod - mod process, then methods Radio advertising revenues showed a 12% other than standard heterodyne processing may be increase in 1978 over the previous year. required for satisfactory stereo operation free The average U.S. household now has at of beats and noise. This is due to inherent non least 5 radios. Of the total number of linearities in the FH detection which causes a radio stations now on the air, approx beating of horizontal sync multiples with the 38 imately 31% bP.aan operation during the Khz stereo sub-carrier frequency. This shows up past decade.{3J The above trends are as distinct annoying audible notes in the stereo indicative of a communications media audio. The beat frequencies are derived as fol that is alive, well and growing in spite lows: of the "video revolution". 3 (15734) - 38000 • 9202 HZ Audible Beat Figure 1 illustrates the fact that in 1979 38000 - 2 (15734) = 6532 HZ Audible Beat Americans spent a total of 9.8 billion dollars on three interrelated audio soy{jes; radio sets, Satellite delivered FM stereo is relatively HI-FI phonographs and records. new and more work remains to be done to maxim ize quality while minimizing bandwidth. Methods EXPENDITURES ON LEISURE TIME PRODUCTS (1979) do exist to transmit excellent quality FH stereo via satellite while keeping the hardware cost to Radio Sets $3.5 billion the cable operatbr reasonable. The Learning sys Hi-Fi Phonographs $3.3 billion tem of enhanced multiplex transmission was chosen Records $3.0 billion by United Video for transmitting the signal of General Interest Books $3.0 billion WFHT-FH, generally regarded as one of the highest Movies $2.65 bill ion technical quality FH stations in the country. All Spectator Sports $2.3 billion Actual proof of performance data verifies that Musical Instruments $2.1 billion this method is probably t?! best available with Film Developing $2.0 billion today's state of the art. ) To summarize the technical considerations, do FIG. 1 Audio Entertainment Is Big Business! not leave them to chance I Individually process the FH sources and pay close attention to trans Let's take a look at what types of aural ser mission methods for imported sources. Quality vices could be provided as part of a cable en must be of paramount importance when consider tertainment package and the reasons for consid ing audio service. ering them. THE (HI-FI) SKY'S THE LIMIT At this point in time, our prime source of Nobody needs to tell us about the television audio service will be derived from local off-air programming variety available to today's cable and imported off-air FH radio stations. It operator. Local off-air, imported off-air (with should be realized that FH radio is growing at a 27 remarkable pace both in quantity and quality.