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IEEE COMMUNICATIONS MAGAZINE UHF AND

PHILIP B. GIESELER

Problems in UHF and insufficient -to-noiseratio at the television receiver ways to improve reception. picturetube. Available evidence suggeststhat this is the dominant difference between UHF and VHF [ 13. We will utilize a model that indicates the level of this signal 1952 the FederalCommunications Commission , N strength handicap for severalsets of assumptions, and adopted a dual allocationstructure for broadcast determine the effects of improvements to the UHF service. television that utilized both VHF (channels 2-13) and UHF frequencies (channels 14-83)., The disparate properties of these two bands have produced COMPONENTS TO THE UHF PROBLEM what has become known as the “UHF handicap”-UHF It may be helpful to review the fundamental reasons why television signals aremore difficult to receive than VHF UHF frequencies are more difiicult to receive than VHF signals and therefore are not as significantly viewed. frequencies, and what some of the possibilities are for The FCC andthe broadcasting industry have been improvement. First, we should recognize that the effective- attempting to overcome the disadvantagesof UHF television ness of receiving antennas in converting field strength to in order toimprove serviceto thepublic from existing stations, follow an inverse square relationship with and to encourage the operationof additional stations, which [8]. For an of constant gain over all channels, a must come primarily from the UHF band. As of late 1979, signal of a given field strength would be 10 dB less effective there were 640 UHF channels vacant andavailable, butonly on 638 MHz (channel 41) than on 195 MHz (channel 10) 84 vacant VHF channels. Many of these vacancies are in and 19 dB less effective than on 71 MHz (channel 4). The isolated areas or are reserved for noncommercial use, but decreasing effectiveness of antennas becauseof frequency is hundreds of additional television stationsare nonetheless perhaps the most severe factor affecting UHF, but there are possible in the UHF band if it was cost-effective for these several others. UHF frequencies, while ideal for unobstructed stations to begin operation. point-to-point transmission, are less than ideal when used for There are at least three possible types of handicaps that broadcasting to the public-at-large located in a variety of contribute to the disadvantage facedby UHF. First, there is nonoptimum receiving areas. UHF is attenuated more by the picture quality handicap. If ghosts, snow, synchroniza- roughterrain, buildings, and foliage than is VHF. The .tion, or other aspects of the television picture affect UHF attenuation through is higher for UHF than more than VHF,there is a picture quality handicap. Second, VHF, and the connections between components are more there is a channel selector handicap. If VHF channels are critical. Electronic devices such as TV receivers contribute easier to tune than UHF channelsand if this results more at UHF frequencies than at VHF. In view oft+ in a disinclination to view UHF, a handicap exists. factors, it is surprising that UHF television works as well as it Finally, there is a programming handicap. Since theappeal of does! particular programmingmay be the dominant reason There are, of course, compensating factors. Ideally, the’ someone will view one channel over another,UHF suffers to gain of television receiving antennas will be several the extent thatthe programming offered on UHF channels is higher on UHF than onVHF. UHF broadcasters areallowed less attractive than thatavailable on VHF channels. This last to operate with much larger than onVHF. Lastly, but handicapcannot be directly addressed throughtechnical significantly, UHF frequencies are not particularly suscepti- improvements, but programming should be recognized as a ble tourban noise (automobile ignitions, industrial ma- contributor to the overall handicap nonetheless. chinery, power lines), whereas VHF can bequite degraded by In this paper we will be discussing only the picture quality this factor. handicap. Furthermore, we will explore only one type of One way to improve UHF signalstrength is for picture quality handicap-the “snow” that is produced by an broadcasters toincrease their (ERP)

US. Government work not protected by US. copyright

46 MAY 1981 up the limit allowed by the This would be an to 5 MW FCC. variety of “what if . . . ” questions. The components to APT, improvement of 6 dB over current average operation of about and the numerical values that will be used as inputs to.them, 1.25 MW. However, UHF broadcasters have much higher are described below. transmission costs than VHF broadcasters. The electrical power costs of UHF stationscan be ten times those of Propagation model VHF stations. This is due not only to the fact that UHF broadcasters must operate with higher Built into the APT computer program is the Longley-Rice power to achieve coverage close to equivalent with VHF propagation model for area predictions [9]. This model is stations, but also to the fact that the technology usedfor UHF particularly suited for the purpose at handbecause of the way transmission is inherently less efficient inconverting electrical it recognizes the probabilistic nature of propagation. power to transmitted power. In view of these costs, operation The Longley-Rice model can generate a prediction of the at high ERP will not always‘be cost-effective for UHF probability of reception at any given distance from the stations. Recently, possibilities for improving UHF transmit- transmitter, whereas with the model generally used by the ter efficiency have been reported [2],[3],[24]. Presumably, FCC [IO], this particular calculation is more cumbersome. lowering the cost of high power. UHF operation will make There is a significant difference, however, between the increased ERP cost-effective for more UHF broadcasters. predictions obtained by the FCC and the Longley-Rice models for frequencies. The Longley-Rice model Anothercandidate for improvement is to reduce the UHF predicts fields up to 13dB higher than the model in the maximum allowed UHF of television receivers. FCC The FCC has already takenaction in this area by lowering the area of interest, as shown in Fig. 1. While part of this previous 18 dB maximum limit to 14 dB, and UHF reception discrepancy is accountable by the broad variability inherent can be expected to gradually improve as these new receivers in UHF propagation, preliminary evidence indicates that the enter the marketplace.’ Longley-Rce model does not account for foliage attenuation The remaining area where improvement is available is in to the same degree theas FCC model [ 111. In the absence of the receiving antenna system [25]. This is perhaps the most additional research required to provide higher confidence in critical component in the television reception chain, but also this area, the UHF predictions provided by the Longley-Rice the most difficult to implement on a wide scale. It depends on model have been adjusted downwards by 10 dB in order to the purchase and proper installation of the most appropriate more nearly correspond to traditional FCC predictions. receiving equipment, which in turn depends on the choices Our calculations will be based on a terrain roughness factor made by consumers. of 100 m, as computed for the Longley-Ricemodel. Because What additional actions will be taken, andto what extent, of differences in the way it is defined, this corresponds to a is the subject of a current FCC proceeding dealing with terrain roughness of 64 m as computed by the FCC and CClR improving UHF television [6]. The present paper will explore procedure [ 121, and is representative of hilly terrain slightly and estimate the approximate effects of improvements that rougher than average. might be made. This will involve estimating the area, and particularly the population that can be served by U,HF and Transmission system parameters VHF facilities, and determining the effects of improvements The TV transmitting characteristics described in Table 1 to the UHF service. will be used in our calculations, and arebased on the average values for licensed stations, except that the VHF effective radiated power is the maximum allowed in the FCC rules, THE AREA-POPULATION TRADEOFFS MODEL since the vast majority of VHF stations operate at this level. In order to makecomparisons of UHF and VHF coverage, The averageUHF ERP of 1250 kW is 6 dB below the 5 MW wewill employ a rather simple but useful computer tool maximum allowed by the FCC. known as area-population tradeoffs (APT), first reported in In the most populated regions in the east (which the FCC [20].* APT employsassumptions about thetransmitting rules define as Zone l), VHF stations with transmitting. system, the receiving system, and the propagation path in antennas greater than 1000 ft must attenuate power in order order to provide estimates of the effective area receiving to limit interference into neighboring markets.About 20 service. It also uses a simple population model for estimating percent of the VHF stations are located in Zone 1. These the population covered. Because APT operateson the stations would serve slightly smaller areas and populations general rather than the specific case, it is useful indetermining than will be estimated in what follows. trends rather than specific results. ‘It allows the user to ask a Receiving system parameters Any estimates of television coverage must make several ’The FCC also acted to reduce this maximum noise figure limit to 12 dB assumptions, both about the receiving equipment which is in effective in 1982, but this was overturned by the US.Court of Appeals. See use and the nature of the receiving environment. The FCC [4] and [5]. has.previously made approximations for rural and urban TV ’The author gratefully acknowledges the contribution of John Murray of the Institute for TelecommunicationSciences, National coverage, and defines Grade A and Grade B contours as and Information Administration, Departmentof Commerce, who developed guides to station coverage. The GradeA contour indicates a the APT program and provided for its use. field strength 30 ft above that is sufficient to provide

47 ~ lEEE COMMUNICATIONS MAGAZINE

90

ao

70

60

50 m1 P i-40 0 “! x 30 k

20

10

0

- 10 0 10 20 30 40 so 60 70 ao 90 110loo 120 130 140 150

DISTANCE IN MILES

Fig. 1. A comparison of the FCC F(S0,SO) curves with the Longiey-Rice model of . Both curves are drawn for a channel 43 transmitter having an effective radiated power of 1 kW and a height above average terrain of 300 m (990 ft) and both assume an average terrain irregularity parameter.

acceptable quality to a receiving installation considered current valuesthat define theGrade B contourappear typical of suburban areas [7], [B]. This signal is predicted to appropriate for VHF, but modification appears tobe in order be provided to the best 70 percent of the receiving locations for UHF. With ourestimates of present-day receiving 90 percent of the time. The Grade B contour indicates a field equipment, detailed in the Appendix, a signal 7 dB stronger strength 30 ft above ground that is sufficient to provide than that originally assumed is required for adequate UHF acceptable quality to a receiving’ installation considered reception. Thus, a “modified Grade B contour” is used in the typical of outlying areas. This signal is predicted to be remainder of this discussion to illustrate station coverage in provided to the best 50 percent of the receiving locations 90 outlying areas. , percent of the time. The FCC also defines a City Grade To illustrate coverage in urbanareas where indoor contour, which is simply a 6 dB higher signal strength than antennas arewidely used, it was felt that a contour depicting that specified for the Grade A contour. indoor receiving antennas would best approximate reception. While these contours are useful, they do not necessarily An “indoor antenna contour” has been derived in the indicate where receptionis adequate or inadequate. They are Appendix using some of the original values for the Grade A probabilistic, and assume that a certain quality of receiving contour, but with appropriate modifications for a prediction of equipment is in use. The FCC’s official contours are chiefly service using indoorreceiving antennas. Themodified Grade administrative ratherthan comparative tools. A more B and theindoor antenna signal strengthcontours arederived accurate comparison of VHF and UHF television can be in order to compareUHF and VHF reception as accurately as realized by modifying some of thetraditional television possible in close-in areasand outlying areas.The field planningfactors. In rural areas whereoutdoor antennas strengths that define the modified contours and the official would typically be used and no urban noise is present, the FCC contours are shown in Table 11.

48 MAY 1981

AREA COVERAGE OF TELEVISION SIGNALS are due to “urban noise,’’ which greatly affects reception of Given the assumptions and models above, we canmake low VHF signals, and also affects high VHFsignals, but does television coverage estimates. Fig. 2 shows how the not significantly affect UHF signals. percentage of locations receiving anadequate signal Our model usesthe information from Figs. 2 and 3 to decreases as the distance from thetransmitter increases.This determine the “effective area” covered by typical UHF and is for the modified Grade B contour (outdoor receiving VHF stations. The effective area is calculated by utilizing a 5 antenna in rural areas). This figure indicates the handicap mi step integration procedure: the area in each 5-micircular faced by UHF, and also shows the advantage held by low ring around the ismultiplied by the VHF over high VHF in servicing outlying areas. The Grade B percent area covered for that ring. All such rings are summed service contour specified by the FCC is for service to thebest and the cumulative totalgives the effective area served. Fig. 4 50 percent of receiving locations. Thus, from Fig. 2, the shows the results for outlying reception (outdoor antennas modified Grade B contour line has a radius of 76 mi for low and no urbannoise). At about 40 mi, the UHF curve begins VHF, 72 mi for high VHF, and ‘45 mi for UHF. (Service to level off, reflecting the beginning of the region where only a extends beyond.these contours in the most favorable small percentage of the locations are receiving an adequate receiving locations, and falls short of the contours in less signal level. VHF stations provide acceptable service to areas favorable locations.) well beyond 40 mi, and their total area coverage is much Fig. 3 is a graph similar to Fig. 2, but for the indoor antenna larger than for UHF. Clearly, the VHF stations hold a contour, and shows that in urban areas,UHF coverage is still tremendous advantage over UHF stations in their ability to inferior to VHF, but that thedifference is not nearly as severe serve outlying areas; they are able to serve aneffective area as in outlying areas. Upper VHF frequencies are superior to of about 18 000 sq mi while a UHF station serves only about lower VHF frequencies in this case. Both of these conditions 6000 sq mi. Fig. 4 also shows the effect of hypothetical signal

49

J IEEE COMMUNICATIONS MAGAZINE

Fig. 2. Outdoor contour. Percent of area receiving coverage versus distance from transmitter. Source: APT model for the modified Grade B contour.

strength improvements to UHF. “Signal strength improve- ment” refers to an increase in signal-to-noiseratio at the television picture tube, achieved by any of many possible means, suchas improving effective radiated power, receiving , receiver noise figure, transmission line loss, or other factorsthat can improve UHF picture quality by decreasing picture “snow.” The figure shows improvements of 6, 12, and 18 dB. The 6 dB improvement can be used to showthe effect of increasing ERP from the 1.25 MW assumed to the 5 MW limit, with no other changes. A 12 dB improvement might be obtainable by upgrading both the receiving system and the transmitted power. An improve- ment of 18 dB is very large and probably is not possible to achieve on a widespread basis. But even with an 18 dB improvement to UHF, VHF stations still hold a substantial advantage (5000 sq mi) in effective area served. The conclusion is clear: in the ability to serveoutlying areas, there is not likely to ever be true equality between UHF and VHF stations. There are, however, two factors that makesignal strength “comparability” an achievable goal. First, television stations 0 10 20 40 30 50 60 70 80 are generally located close to high population centers. Since most of VHF’s advantage is in serving outlying areas, UHF DISTANCE FROM TRANSMITTER, MILES stations may be ableto reach the great majority of the population served by VHF, even though the UHF service ig. 3. Indoor contour. Percent of area receiving coverage versus distance from transmitter. Source: APT model for the area is proportionately muchsmaller. In theory, VHF stations indoor antenna contour. would be able to serve distant population centers not

50 MAY 1981

11 DISTANCE FROM TRANSMITTER, MILES

Fig. 4. Cumulative effective area covered versus distance from transmitter using assumptions for outdoor receiving antennas. Source: APT model for the modified Grade B contour. reachable by the UHF stations, but in practice much of the density falls off with distance. This model is designed to population in such areas may notwish or be able to view the estimate urban and suburban, but not outlying population distant stations. The second factor that aids the goal of UHF densities since the value for PD eventually goes to zero. Our comparability is that the above results reflect estimates of technique employs a modification of this population density reception in rural areas; coveragepredictions in urban areas, formula to ensure that a minimum density is maintained: that include the degrading effect of urban noise on the VHF PD(d) = PDmin PD e-bd (2) bands, are more encouraging. We shall examine each of + .. these factors in turn. where PDmi,is the population density of outlying areas. This formula can be applied to the previous procedure to POPULATION PREDICTlONS estimate the population served by UHF and VHF stations. The APT technique can beused to estimate the population For each 5 mi ring, the effective area previously calculated is served by various station configurations by incorporating a multiplied by the population density in that ring. Results from simple model used by urban planners that attempts to model each 5 mi increment are summed to determine the overall population distribution characteristics [ 131: population served. TO illustrate the population coverage model, PD,,, will be PD(d) = PD e -bd (1) set to 10 000 people/sq mi, PD ,,,in will be set to55 people/sq .where PD(d) is the population densityat a distanced from the mi, and b will be set to 0.20. Values for PD,,, and b are city center, PD,,, is the population density at the city center approximations of Houston estimates from [ 131. PDminwas (which in this case is also assumed to be the transmitter site), derived fromoutlying rural areas surroundingColumbus, and b is a constant that determines how rapidly population OH. We will also assume a maximum range of 75 mi. That

51 IEEE COMMUNICATIONS MAGAZINE

is, it is assumed that beyond 75 mi, no one is viewing the UHF and VHF area coverageis not as large as in the outdoor even if it is available in a portion of the antenna case. At distances of 15, 30, and 45 mi, the UHF receiving locations. The total population within the 75 mi station serves a cumulative area of88,67, and 53 percent of radius’is about 2 million people. the .VHF area, respectively. (Recall thatfor the outdoor Population Distribution 1 in Table Ill shows the hypo- antenna at 75 mi the UHF station only served 44 percent of thetical results for the area and population served by UHF the VHF area.) and VHF stations. The high VHF and low VHF results were Population estimates were made for the indoor assump- averaged, and this average compared to the UHF area and tions, and improvements to the UHF service were hypothe- population. While the UHF station only serves 44 percent of sized. Results are shown in Table 1V fora maximum rangeof the area of the VHF average, it serves 80 percent of the 30 mi. For thethree cities, UHF population coverage is population. The table also shows the effect of improvements estimated to be 86 percent of VHF coverage or larger. A 6 to the UHF service. dB improvementto theservice is estimated to provide In order to determine the sensitivity of the data’ to other coverage to at least 96 percent of the population receiving population distributions, additional hypothetical results were VHF indoor service. obtained for a larger city with densely populated outlying areas, and a smaller city with sparsely populated outlying areas. The largercity parameters are based on estimates for “REAL WORLD” ESTIMATES Boston (PD,,X = 20 000, PD,;, = 120, b 7 0.2, total The aboveestimates, while useful, donot in fact population about 4.5 million). The smaller city parameters correspond to television reception in the real world. In one are based on estimatesfor Phoenix (PD,,, = 10 000,PDmin case, they assume that everyone has an indoor UHF and = 6,b = 0.3, total population about 450 000). Results for VHF antenna, i.e., noone uses outdoor antennas. This these cities are alsoshown in Table Ill. With anarea assumption isclearly suspect. In the other case, they assume coverage of 44 percent of the average VHF coverage, the that everyonewho needs an outdoor antennauses an outdoor UHF station in the largercity has a population coverage of 75 antenna of a quality necessary for adequatereception, up toa percent, andthe UHF station in the smaller city has ,a certainmaximum quality. Information from the TASO population coverage of 89 percent. Report [23] is consistent with this latter assumption: The magnitude of the UHF handicap appears to be very large when the area of coverage is compared to VHF, and [AISone goes farther andfarther from a transmitter, much smaller when population coverage is used as the one finds the quality of the receiver installations, and reference. Further, a smaller handicap is predicted when the particularly the quality of the receiving antennas, particular television market is small in areaor when the improves so that the decreasein signal strength is to a outlying areas of the market have low population. considerable extentcompensated . . . The effect The area receiving service with indoor antennas is shown in produced is that, overa considerable range of distances Fig. 5. As expected,the figure continues to show an from a , picture quality, as advantage for the VHF stations, but the differential between observed in the home, remains at approximately the

52 MAY 1981

v) W 2 3,000 8 E0 V

$V 0

Fig. 5. Cumulative effective area covered versus distance from transmitter using assumptions for indoor receiving antennas in urbanized areas. Source: APT model for the indoor antenna contour.

TABLE 1V ESTIMATES OF EFFECTIVE AREAAND POPULATION COVERAGE FOR kDOOR RECEIVING MTENNAS IN URBANIZED AREAS AT A RANGE OF 30 MI (UHF results are given as a percent of the VHF average coverage)

Population Covered Area Distribution #1 Distribution #2 Distribution #3 cover& (total pop.: (total pop.: (total pop.: 2 millicn) 4.5 million)450,000)

low VHF 1872 sq.984,6132,428,766 mi. 350 ,657 high VHF 2279 sq. mi. 1,058,935 2,607,452 362 ,922 VHF average 2075 sq. mi. 1,021.,774 2,518,109 356,789

UHF86% 67% 86% 92%

UHF Improvement

88% 96% 96% 98% 96% +6 dB96% 88%

same satisfactory level; but that when some more or ment, and hence adequate VHF reception, in comparison to less critical distance is exceeded, the service deterior- UHF receiving antennas and UHF reception. For noncable ates very rapidly. (p. 15) households in intermixed markets, 46 percent use outdoor antennas, 48 percent use an indoor antenna, and 3 percent Based on theTASO work, the notion has been that viewers use an attic antenna.3Of those who use outdoor antennas, 9 1 will do what is needed to receive a television signal until that percent use an outdoor antenna for VHF, but only 50 percent signal is very difficult or impossible to receive. In an use an outdoor antenna for UHF. Of those who haveno intermixed UHF/VHF structure, however, this does not hold true for reception of UHF signals. A recent survey of 32 percent were attached to a master antenna system, and 2 percent viewers in intermixed markets [l] a reported using no antenna. These percentages referall theto antenna used disproportionate amount of VHF receiving antenna equip- with the most frequently watched.

53 IEEE COMMUNICATIONS MAGAZINE outdoor antenna, 96 percent have a VHF indoor antenna, but only 7 1 percent report a UHF indoor antenna. Of those who were predicted to receive adequate UHF reception only if an outdoor antenna were used, i.e., were located beyond the indoor antenna contour, only 33 percent did in fact have an outdoor UHF antenna. The survey findings tend to confirm the conclusion of TASO for VHF, but not for UHF receiving antenna installations. This is not unusual given that the most popular programming is generally on VHF channels and that VHF signals can be more easily received. Our coverage estimates are still quite useful because they indicate the potential for UHF, if and when most homesare equipped with UHF receiving antenna equipment comparable in quality to VHF equipment. The current level of UHF coveragecan be roughly estimated by incorporating the antenna distribution results given.above against the indoor and outdoor coverage predictions already made. First, we assume that all viewers' who are predicted by APT to receive a VHF station using outdoor antennas use the equipment necessary so they do obtain reception. (In some cases, indoor VHF antennas will be sufficient.) This is consistent with the conclusion of TASO. Second, we assumethat, of those viewers predicted by APT to receive a UHF station using indoor antennas, only 7 1 Fig. 6. Effect of terrainon UHF coverage. Percent of area percent currently receive service since29 percent do not have receiving coverage versus distance from transmitter for UHF a UHF indoor antenna. Third, of those viewers predicted by stations in areas of slightly rolling plains (delta h = 30 m), hills APT to receive a UHF station only if an outdoor antenna is (delta h = 100 m), and mountains (delta h = 300 m) using used, we assume that only 33 percent obtain reception since assumptionsfor outdoor receiving antennas.Source: APT model for the modified Grade B contour. the remaining 67 percent do not have a UHF outdoor antenna. From Table IV, using population distribution 1, those receiving UHF service from indoor antennas are CONCLUSION 1 021 774 X 86 percent X 7 1 percent = 623 895. The preceding results should not be interpreted as precise. because specific station operations vary considerably from From Table 111, thoseadditional viewers receiving UHF theaverage parameters assumed for frequency, effective service from outdoor antennas are radiated power, antenna height, and surrounding terrain. The methodology employed inherently deals with the general case (1 788 653 - 1 021 774) X 80 percent X 33 percent anddoes not necessarily defineoperation in a particular = 202 456. market. It is believed, however, that the general trends have The total receiving UHF service is 826 351 or only 46 been accurately shown. percent of those estimated to receive VHF service. Fig. 6 indicates the difference in UHF reception in slightly Similar results can be obtained for the other population rolling plains, hills, and mountains, and shows that UHF distributions and for different assumptions of antenna reception suffers significantly in areas of rough terrain. ownership and reception. Estimates of the UHF handicap would be much greaterwhen Our results suggestthat, even though abouteight out of ten mountainous terrain is assumed, and somewhat less when households that receive adequate VHF could receive nearly flat terrain is assumed.Each television market is adequate UHF reception merely by. installing appropriate unique and will vary from the population distribution patterns receiving antenna equipment,only about five out of ten assumed. households have done so. Another way of looking at this is With several qualifications, however, we have shown that that improvements to UHF signal strength of 6 dB or even12 in spite of its technical disadvantages, UHF television is dB as given in Tables 111 and IV, while significant, would not capable of providing coverage to a significant portion of the offer as muchimprovement as would be obtained from a more population that receives coverage from VHF television pervasiveuse of UHF receiving antennas, SO thatthe stations. By far the largest component achievingfor this goal assumptions that make up the modified television planning appears to be the purchase and installation of good quality factors are in fact realized. UHF antenna equipment.

54 MAY 1981

1 ine loss 6 from E151

APPENDIX Location Variability Factor: This is used to modify The APT predictions in the text are based on various F(50,SO) curves that predict service at 50 percent assumptions for receiving equipment andthe receiving of thelocations to F(70,50) curves that predict environment. The FCC groupsthese various assumptions service to 70 percent of the locations. under the heading of “television planning factors,’’ and uses For Indoor Antenna Predictions: them to define the field strengths required for the FCC’s Grade Building Penetration Loss A and Grade B contours. The text uses planning factors that For fringe area’ reception, the FCC’s Grade B contour have been modified from values in order to compare the FCC corresponds to a signal level of 47, 56, and64 dBu4 for low service from UHF and VHF television somewhat more VHF, high VHF, and UHF, respectively. Previous analyses accurately thanwould be possible if the Grade A and GradeB have shown that, although individual planning factor values contours were used to compare UHF and VHF coverage. have changed, these changes tend to cancel one another in The planning factors consist of the following elements for the VHF bands and theFCC’s original values continue to be prediction of fringe area reception. reasonable for VHF fringe reception [ 141, [ 151. For UHF, the values in Table V were used, and show that a 71 dBu field Receiving Equipment strength is appropriate for fringe reception estimates. This is 7 Receiver Noise Level: This is the inherent thermal noise dB higher than that used by the FCC for its UHF Grade B level of an ideal receiver. contour. Receiver Noise Figure For urban reception with indoor antennas, changes from Required Signal-to-NoiseRatio for anAcceptable the above formulation should be made in antenna gain [ 181 Picture and line loss (assumed negligible for indoor antennas). A Dipole Factor: This indicates the efficiency of a dipole fact& for building attenuation should be included [ 191. Since antenna in converting field strength to signal strength reception distances closer to the transmitting antenna are for the frequency of interest. more typical of reception with indoor antennas, different factors for time and location variability are used [lo]. Finally, Receive AntennaGain Relative to a Dipole 5 Transmission Line Loss an urban noise factor is included (identical to the factor that the FCC uses for the GradeA contour). Table VI shows dBu Receiving Environment values for the indoor antenna contour. For all Predictions: For comparison, Table VI shows the FCC values for the Time Variability Factor: This is used to modify City Grade contour. The indoor antenna contour is 8- 10 dB F(50,50) propagation curves that predict service higher than the FCC values for VHF, but 21 dB higher than 50 percent of the time to F(50,90)curves thatpre- the FCC value for UHF. This is further evidence that the dict service 90 percent of the time. official contours, while perhaps administratively useful, For Urban Area Predictions: Urban Noise Factor 4dBu is defined as decibels above the microvolt per meter.

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[lo] J. W. Damelin, W. Daniel, H. Fine, and G. Waldo, “Development of TABLE VI VHF and UHF propagation curves for TV and FM broadcasting,” PLANNING FACTORSFOR THE kDOOR, ANTENNA CONTOUR FCC, Rep. R-6602, Sept. 1966. [I 11 J. T. Cochrane, Jr. and F. Boldissar, “An analysis of field strength contours forpublic broadcasting service television stations,” DoD . Compatibility Analysis Cen. Rep. ECAC-PR-78-010, Mar. 1978. receivernoise level [12]CClR Document Draft, Rep. 567-1 (Rev. SO), “Methods and statistics for estimating field strength values in the land mobile services recelvernoise figure using the frequency range 30 MHz to 1 GHz,” Document 5/40 E, Feb. requiredsignal-to-noise ratio 20, 1980. of dipolefactor [13] E. S. Mills, Studies in the Structure the Urban Economy. Baltimore, MD: Johns Hopkins Press, 1972. receive antenna gain [14] G:S. Kalagian, “A review of the technical.planning factors of VHF lineloss television service,” FCC, Rep. RS-77-01, Mar. 1977. [15] P. B. Gieseler, V. D. Armstrong, A. D. Felker, and S. R. Brenner, timevariability factor (93%) “Comparability for UHF television: A preliminary analysis,” Appendix locationvariability factor (70%) 4. 4 6 8,UHF Comparability Task Force, FCC, Sept. 1979. NTlSaccession , number PB301267/AS. to overcm urban noise 14 7 0 [16] S. R. Lines, “A survey of certain performance characteristics of buildingpenetration loss -17 -20 -24 television receivers,” Office of Chief Engineer, FCC, Tech.Div. RepT- 82 dbu 87 dbu 101 dbu 7201, June 1972. [17]W. R. Free and R. S. Smith, “Measurement of UHF television receiving antennas,” Georgia Inst. Technol., Atlanta, Eng. Experi- Present FCC signallevel for the ment Station, Project A.2066, Feb. 1978. City Grade contour. 74 dbu 77 dbu 80 dbu [18] R. G. FitzCerrell, “Indoor television antenna performance,” NTlA Source: see appendix text Rep. 79-28,Oct. 1979. NTIS accession number PB80-126 598/AS. [19] G. V. Waldo, “Report on the analysis of measurements and observations, New York City UHF-TV project,” FCC, Rep. R-6303, Mar. 27, 1963. [20] J. P. Murray, “Comparativeperformance of VHF and UHFtelevision broadcast Signals,” unpublished paper, Inst. for Telecommun. Sci., Nat. Telecommun. and Inform. Admin., U.S. Dep. Commerce, should not be considered as predicting the same quality of May 15, 1977. reception for UHF as they do for VHF. The estimates in the [21] P. I. Wells and P. V. Tryon, “The attenuationof UHFradio signals by text are likely to provide a better comparison. houses,” Office of Telecommun., U.S. Dep. Commerce, OT Rep. 76-98, Aug. 1976. Values for the receiving environment different from those [22]CClR Document Draft, Rep. 258-2 (Rev. 76),“Man-made radio I used here have been reported by some. Lower UHF building noise,” Conclusions of Interim Meeting 6f Study Group 6, May 17, are is 1976. penetration losses reported in [21]; VHF urban noise [23] Television Allocations Study Organization, “En@neering aspects of reported as several decibels higher than our values by [22]. television allocation,” Rep. to the FCC. Much of this report has been The values used were based on what appeared to be most reproduced in Proc. IRE, June 1960. appropriate under the particularcomparative circumstances, [241 P. B. Cieseler, V. D. Armstrong, S. R. Brenner, A. D. Felker, and F. 0. Setzer, “Comparability for UHF television:Final report,” with due regardfor the uncertainties regarding present UHF Comparability Task Force; FCC, Sept. 1980. knowledge of a subject as complex as the receiving [25] W. R. Free, J. A. Woody, and J. K. Daher, “Program to improve environment. UHF television reception,” Georgia Inst. Technol., Atlanta, Eng. Experiment Station, Contract FCC-0315, Sept. 1980.

REFERENCES [l] Harris, Louis and Associates, “A survey of consumer attitudes and , experience regarding UHF television,” J.M. Boyle Project Director, Study 792806, Sept. 1980. [2] C. C. Cutler, “New technical opportunities for UHF television ,” Rep. to the UHFComparability Task Force, FCC, Feb. 1980. [3] J.T. Wilner, and T.B. Keller, “UHF-TV transmitter improvements progress report,” PBS Eng. Rep. E8012, July 30, 1980. [4] “Report and order” in Docket 21010, UHF Television Receiver Noise Figures, 70 FCC 2d 1176, 1978. Philip B. Gieseler was born in Washington, DC, [5] U.S. Court of Appeals forthe District of Columbia Circuit, “Electronic on January 5,1949. Hereceived the B.S. degree Industries Association vs. F.C.C.,” case79-1197, decided Sept. in from North Carolina 17, 1980. State University, Raleigh, in 1971. [6] “Notice of inquiry” in Docket 78-391, Improvements to UHF Since 1972he has been employed by the Teleoision Reception, 44 F.R. 3656, 1979. Federal Communications Commission, first in the [7] “Third notice of further proposed rule making” in FCC Dockets 8736, Field Operations Bureau and then in the Broad- 8975, 9175, and 8976,Appendix B, FCC 21-244, Mar. 24, 1951. [8] R. A. O’Connor, “Understanding television’s grade A and grade B cast Bureau. Since 1977 he has worked in the service contours,” IEEE Trans. Broadcast., vol. BC-14, pp. 137-148. FCC‘s Office of Plans and Policy, initially as a [9] A. C. Longley and P. L. Rice, “Prediction of troposheric radio member of the UHF TaskForce, and in 1979 and transmission over irregular terrain-A computer method,” ESSA 1980 as Program Manager of the UHF Comparability Task Force. He is Tech. Rep. ERL 79-ITS 67, 1968. currently a member of the Technical Staff of O.P.P.

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