Microwave Electronic News Gathering Chapter 3: Television Field Production Z Chapter 4: Telephone Systems and Interfacing Cc
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z o Chapter 1: Radio Field Production F- Chapter 2: Microwave Electronic News Gathering Chapter 3: Television Field Production z_ Chapter 4: Telephone Systems and Interfacing cc co cc o a w o w oc mg M1111111 ma 7 t w 6.1 Radio Field Production Jerry Whitaker Editor Broadcast Engineering Magazine Overland Park, Kansas Radio stations have used the remote location is heard at such gatherings, resist the urge to be broadcast for decades to bring the listener an negative when someone asks for a level of per- added sense of realism and excitement. Although formance that is not practical. Hear everyone out. the concept of the remote -as it is better Even though the engineers present at the meetings known -has not changed substantially over the may know that it is impossible to provide every years, the means to accomplish the task has been reporter on the staff with a separate frequency quantum leaps in performance, ease of operation that can be received at the studio from anywhere and reliability. Radio Electronic News Gathering in town, at least listen to what the users would (RENG) systems of today can be configured to like the system to do. The realities of station provide virtually any degree of sophistication re- economics and the laws of physics can be ex- quired by the station. As with any other area of plained after the desires of the participants have broadcasting, the key to a successful RENG sys- been outlined. Many -perhaps most -RENG sys- tem is thoughtful planning. tems were built on a piecemeal basis, as needs dictated and economics allowed. The lack of a unified plan has often lead to RENG systems that PLANNING THE NETWORK are cumbersome to operate and -in the long run -more expensive than necessary to build for a The importance of careful planning of a RENG given level of performance. system cannot be over emphasized. The network The size and layout of the station's market will should be configured based on the precise needs have a substantial effect on how the RENG net- of the station. All persons that will be involved work is designed. A system intended to cover a in the use of the system should be consulted to sprawling urban area of 10,000 square miles will determine just what type of arrangement will be be configured much differently than a tightly needed. Whether a station's format is "all news" clustered urban center covering 2,000 square or, "AOR," all persons in the news, production miles. The number of stations in the market that and engineering departments should sit down and are involved in RENG activity may also affect define the requirements of the network. Whatever how a system is designed, and what types of equipment are used. Stations in major metro- Additional information for this chapter was provided by Richard A. politan areas may find that few, if any, frequen- Rudman; Engineering Manager, KFWB Radio; Los Angeles. cies are available for RENG activity. 6.1 -1 6.1-2 Section 6: Remote Program Origination Program material can be returned from the WIRED SYSTEMS field to the studio though either of two common for news, sports routes -wired telephone lines or wireless trans- Wired communication systems can a number of different mission systems of various types. The route back or programming take telco equalized loops to sophis- to the studio will depend upon a number of fac- forms, from basic -line frequency extension tors, including the location of the event, the ticated single or multi dial -up network. An equalized availability of telephone lines, the amount of set- systems using the user a simple, reliable link to the up time provided and the duration of the broad- line offers the The drawbacks include inflexibility, in- cast. studio. stallation lead -time and installation or rental costs. Using the dial -up network gives the user Wired vs. Wireless a greater degree of flexibility than with standard loops, however the level of performance Until the 1960's, the word "remote" was rare- equalized (when a bandwith extension system is not used) ly spoken without reference in the same sentence leaves a great deal to be desired. The most to "the telephone company." Wired systems, popular way around this problem is through the either using the dial -up network or leased broad- use of a 2 -line frequency extender system, as il- cast loops, provided the vast majority of inter- lustrated in Fig. 1. connections from remote broadcast sites to a sta- There are a wide variety of extension methods, tion's studio facilities. Since that time, however, each with a different way of accomplishing the radio systems have assumed an important role in speaking, however, audio from remote activities because they inherently offer task. Generally the remote source is split into two frequency greater flexibility and generally provide the user bands by a filtering network. The higher frequen- with a higher -quality audio link. cy components are shifted lower by a conversion ideally suited for broadcasts Radio systems are circuit for application to the telephone company duration from a variety of loca- of relatively short dial -up network. The lower frequency compo- course of a week's time). Meet- tions (during the nents are shifted upward by a second conversion and sporting events, however, are ings, speeches circuit and applied to a second telephone line. a wired arrangement. probably best handled by At the studio demodulator end, the two signals frequency congestion in the The amount of are frequency- shifted back to their original values, will also have an effect on which origination area filtered and re- combined to form the output of will choose for the greatest reli- method a station the system. Variations on this method include the in which secure RPU chan- ability. Urban areas use of single or multi -band compressors, variable to nels are difficult to find may be best -suited equalization and compandor circuits. The use of a wired link. audio compression at the transmitting (remote) The amount of lead -time given the station be- point, and reciprocal expansion at the receiving fore various events that need to be covered will (studio) end, can provide a substantial reduction also have a significant effect on the route taken in apparent line noise. from by the program audio back to the studio An interesting application of a single -line en- that are scheduled the remote site. Broadcasts coder /decoder is shown in Fig. 2. Audio from obvious candidates for use weeks in advance are a news or sports story is recorded at high speed loop. Spot news events, of a telephone company on a two -speed tape recorder. When the material do not lend themselves to on the other hand, is fed to the station, the low speed is used and let weeks in ad- planning days in advance, alone the recorder output is fed through a single -line a radio vance. In such applications, therefore, bandwidth extension system. At the studio end, system is most practical. the feed is recorded on the low speed of another The cost of telco facilities must also be con- 2-speed machine. When the program material is sidered. Unless the loop is to be left in place for played back on high speed at the studio, an effec- a long period of time, installation charges can tive doubling of frequency response at the high become prohibitive, especially if high-perfor- end is achieved. With this arrangement, it is thus mance equalized lines are needed for the applica- possible to squeeze a signal bandwidth of 100 Hz- the cost tion. Many stations are able to justify 5 kHz through a single dial -up telco line. Corn - of a RENG radio system based solely on the telco panding circuits, if used in the bandwidth exten- savings that can be anticipated. sion unit, will also improve the line's apparent This discussion does not mean to imply that signal -to -noise (S /N) performance. stations should choose between either a wired link Large -scale systems are often or a wireless system. Remote built using both interconnection methods, either Setting Up a Wired as various links in the chain or as back -up pro- If a wired remote is chosen for a particular tection, in the event of a partial system failure. broadcast, the station has a number of options Chapter 1: Radio Field Production 6.1 -3 MODULATOR TERMINAL DEMODULATOR TERMINAL r TELEPHONE LINE 1 - - - - - - - 4002850 Ha LOWPASS FREQUENCY O UENCY LOWP ASS FILTER SHIFTER SHIFFRETER FILTER 502500 Hz «350 Hz -350 Hz 502500 Hz AUDIO AMPLIFIER AUDIO INPUT SPLITTER ADDER ( OUTPUT 504950 Hz 504950 Hz TELEPHONE LINE 2 I 4002850 Hz HIGHPASS FREQUENCY FREQUENCY HIGHPASS FILTER SHIFTER SHIFTER FILTER 25004950 Hz -2100 Hz 2100 Hz 2500-4950 Hz L Fig. 1. The basic two -line frequency extension process for dial -up telephone links. (Courtesy of C. N. Rood.) 50Hz- 2.5kHz 50H0.2.5kHz TELEPHONE LINE TAPE RECORDER 400Hz- 2.55kHz TAPE RECORDER FREQUENCY FREQUENCY AUDIO SHIFTER SHIFTER -1AUDIO INPUT N b Q-Q + 350Hz 350Hz Q_CD 0UTPUT 100Hz-5kHz 100Hz.5kHz RECORD AT 7Y.Ip1 RECORD AT 3' /.Ips PLAY AT 3z/.Ips PLAY AT 7'Alps Fig. 2. A frequency doubling technique using 2 -speed tape recorders and a single -line bandwidth extension system. (Courtesy C. N. Rood.) in terms of equipment and configurations. The telco lines. Generally, however, any audio loop decision on how to originate the remote location that goes through more than one exchange should programming will depend upon the requirements be left to the phone company, which has had of the particular broadcast.