Broadcasting Telecasting (Jan-Mar 1955)

coverage area for a specific station lineup, but this does not help us in determining the coverage of any one station (either on a spot or network basis) nor does it tell us how much duplication exists between stations on the lineup. Advertisers are spending vast sums of money today in television, but the broadcasting industry is reluctant to support a survey which will show these advertisers what kind of coverage they are getting. We believe that the burden of proof is on the networks and the stations and that they should supply the advertisers and agencies with good sound television coverage data. In the absence of any available method for determining the "can and do" area for all television stations, we must rely on an engineering concept to define a television station's primary coverage area. The one that we believe is the best measurement is the FCC definition of Grade B area. This is an engineering concept of signal strength and is defined by the FCC as the area in which an acceptable signal is available to the average home in 50% of the area 90% of the time. This can be determined according to formula, given the effective radiated power, antenna height above average terrain, and channel number. In many cases, these maps (for current operating conditions) were filed with the FCC at the time the application for the station was made. In other instances, however, a station is now on a higher power, has changed its transmitter location, or is using a different height tower than that filed with the original application. If no map is available under these circumstances, we have found the Headley-Reed slide rule invaluable. This slide rule translates the engineering formula based on power, an TELEVISION COVERAGE: AS BROADCAST coverage problems are no novelty to Comdr. Tunis Augustus MacDonough Craven, former FCC Commissioner, FCC chief engineer and Navy communications officer. Testifying in the early 1930's at a hearing before the Federal Radio Commission (predecessor to the FCC), Comdr. Craven was the first to point out that a radio station's coverage was dependent on its frequency as well as on its power and that stations assigned to opposite ends of the standard broadcast band had quite different coverage patterns. ANY USER of advertising would like to know in advance just what results his expenditures will produce. This being an imperfect world, no such complete answer is possible; all the buyer can do is analyze all the information at his disposal before the campaign begins and estimate its probable results on the basis of this analysis. When the medium is television, an important part of the buyer's advance information is the coverage of the station or stations he is considering using. Stations base their estimates of coverage on requirements set by the FCC for Grade A and Grade B service. These requirements are stated in terms of engineering measurements, terms which the timebuyer needs to understand if he is to know what coverage he is buying. What follows is an attempt to explain these technical requirements in non-technical terms. Grade A service is service with a relatively high value of signal intensity. This means that when a Grade A signal is available to a receiver, the picture is clear, vivid, steady and, in general, free from bars, flip-flopping, "snow" or other unattractive features. The picture signal is easy to tune in. Grade B service, with a relatively low value of signal intensity still offers good coverage in the suburbs and the surrounding rural tenna height, and channel number into the FCC definition of Gradfl B service area, so that it is possible to determine the Grade B sen ic area of the station. The coverage area, so determined, has to be circle. Topography, of course, has a great deal to do with a st; tion's coverage area, but it is impossible for the layman to translat the Headley-Reed slide rule circle to a topographical map. We do have several "do view" sources available to us whic enable us to define more accurately a station's coverage area. Thes include^ the local rating surveys such as ARB, Hooper, Pulse ani Videodex, and also the ARB and Videodex uhf studies. Once in formation from local rating and uhf studies are combined wit] engineering maps, we have a "can and do" definition of a station' coverage area. Television stations are making as many and possibly more exag gerated coverage claims than radio stations and certainly are pres suring agency timebuyers to a much greater extent. Thus, as ii radio, it is necessary to weed out the promotional color from sta tion claims before we can get anywhere near a sound definition o a station's coverage area. However, all stations' stories should bt listened to. Many times they have data not available anywhere elst 1 (such as independent surveys and information from local televisior a service men.) These are certainly important and should not be I overlooked in deciding a station's coverage area. In summary, it is evident that there is no one method for determining station coverage and, therefore, as in all media decisions it is' probably necessary to use logic and common sense to almost as great an extent as engineering data and statistical surveys. areas. Some fading may occur, particularly at long distances from the transmitter, but rural area residents generally will have little trouble from the ghost images that plague big city dwellers when signals are ricocheted off T. A. M. CRAVEN neighboring buildings and reach the set later than the direct signals, to produce the ghostlike effect. The limits of Grade A and Grade B service can be represented on a map by contour lines enclosing the service areas. The FCC concept of the extent of Grade A coverage is an area at whose outer limits a signal considered satisfactory by the average viewer may be expected to be available to 70% of receivers at least 90% of the time. In the case of Grade B service, the FCC figures are 90% of the time at 50% of the receiver locations. These are minimum standards to the Commission (although not necessarily to viewers, who seem able to watch with pleasure programs of picture quality too low to be accepted to people living in areas of better reception). As one moves in from the outer edges of the service areas towards the transmitter, the received signal intensity increases; that is, the specified grade of service. A or B, is available to more tv homes more of the time. It is possible to estimate the coverage of a tv station according to an FCC formula which indicates how far a signal would reach if broadcast on a certain frequency, at a certain power, from an AN ENGINEER DEFINES IT ■IHHnHBBMBm Page 40 • January 17, 1955 Broadcasting • Telecasting