Broadcasting Telecasting (Apr - Jun 1952)

k number of parties32 contend that t would be possible to provide adJitional assignments in many locations if the stations at such localises were limited to power less than ;he maxima. For example, it is stated that if-two stations serving small communities operate with ninimum power they could be located as close as 73 miles co-chanlel and 19 and 25 miles adiacent channel for Channels 2-6 and 7-13, respectively, while at the same time receiving the same grade of protection offered by a separation of 180 miles shown in the Commission's standards. The parties accordingly have requested that the Commission provide for additional assignments at reduced power where such Assignments will not cause interference greater than would exist under the prescribed minimum spacings. 137. The Commission does not believe that limited power stations should be provided for in the Table of Assignments at this time in order to squeeze in additional assignments. The effect of low power combined with close spacing is to reduce the interference-free coverage area of such stations, thus providing a sharply limited service. In the example cited above of two stations operating with minimum spower (1 kw effective radiated power) and separated 73 miles cochannel, the interference free Grade A service would be confined to 11 miles and the Grade B service to 14 miles. Further, the proposals for low power stations are all based upon operation of the cochannel stations with an antenna height of 500 feet. As the antenna heights of co-channel stations increase, the service area of the lower powered stations would decrease. 138. Further, these proposals rest on the implicit assumption (that where interference is not caused to the Grade A service of a station, the minimum separations may be reduced below the standards adopted by the Commission. The television Assignment Table and the Rules with respect to television, however, recognize no protected contours. Rather they are based on the concept of affording each station the widest coverage possible consistent with an efficient utilization of the spectrum and the satisfaction of the needs of the various cities and communities in the United States. The Commission in considering grades of service in this proceeding has utilized the principle of iso-service contours. Basic to this principle is a recognition of the fact that, even though "objectionable interference" may not be caused in any contour, an inevitable degradation of service 32 Pennsylvania Broadcasting Company, Philadelphia, Pa.; Southeastern Broadcasting Company, Macon, Ga.; Middle Georgia Broadcasting Company, Macon, Ga.; The Brockway Company, Water| town, N. Y.; Hampton Roads Broad| casting Corp., Norfolk, Va.; Jacksonville Broadcasting Company, Jackson! ville, Fla.; Loyola University of the South, New Orleans, La.; The Gazette I Company, Cedar Rapids, Iowa; Tele' graph Herald, Dubuque, Iowa; KingsI port Broadcasting Company, Kingsport, Tenn.; Michigan State College, East Lansing, Mich.; Hartford Times, Inc., Hartford, Conn.; Travelers Broadcasting Service Corp., Hartford, Conn.; Southern Minnesota Supply Company, Mankato, Minn., and Indiana Technical College, Fort Wayne, Indiana. occurs. We have above discussed at length the basis for the separations we have established. The proposals here cannot be accepted because they are contrary to the basis upon which the co-channel separation requirements have been established. 139. Also to be considered is the safety factor we have previously mentioned. If we should find at a later date the interference which stations may suffer is greater than we have predicted upon the basis of available data, generally only Grade B service will suffer whereas the impact on Grade A service will be little, if any. Moreover, power could then be reduced if it were decided that the interference should be reduced. But in the case of stations operating with lower power at reduced separations it would be more difficult to further reduce power and the service that would generally suffer would be Grade A service. 140. Accordingly, the Commission finds that it must deny the requests of the parties seeking additional assignments where such assignments would require operation at less than the maximum powers specified in this Report. 141. In establishing the co-channel assignment spacing requirements set out above, we have considered carefully the comments and evidence of all the parties who have requested assignments at spacings below the minima adopted herein. Insofar as we have reduced the minimum assignment spacing in Zone I from that proposed in the Third Notice, the requests of certain of the parties for reduced minimum assignment spacings have been granted. We find, however, no adequate basis on the record for granting any of the other requests for reduced minimum spacings and we have found no convincing reason to deviate from our minimum assignment spacings in acting on any specific counter-proposal in this proceeding. 142. The following is a summary of the minimum co-channel assignment spacings provided for herein : VHF UHF Zone I 170 miles 155 miles Zone II 190 miles 175 miles Zone III 220 miles 205 miles Classes of Stations: Powers and Antenna Height 143. In the Third Notice, the Commission stated: The Commission's Notice of Further Proposed Rule Making issued July 11, 1949, provided for three classes of stations, i.e. community, metropolitan and rural stations. During the hearings on the General Issues relatively little comment was offered concerning the proposed classifications. In reviewing this proposal, the Commission has concluded that it is desirable to reduce station classifications to a minimum and that more than one class of station is unnecessary if provision is made for appropriate power ranges for the various sizes of cities and rural areas. Accordingly, only one class of television broadcast station is proposed, with provision for minimum and maximum effective radiated powers in ac Channels 2-6 7-13 14-83 cordance with the respective tables set forth below: (1) Minimum Power Population of Minimum effeccity (excludes tive radiated adjacent metro power1 (in db politan areas): above 1 kw) Above 1,000,000 17 db/500 ft. Ant. 250,000-1,000,000 10 db/500 ft. Ant. 50,000-250,000 3 db/500 ft. Ant. Under 50,000 0 db/300 ft. Ant. 1 Or equivalent, based on the same Grade A service radius as with these values of effective radiated power and antenna height above average terrain. A chart showing this relationship is attached to Appendix B and identified as Appendix IV. No minimum antenna height is specified. However, wherever feasible, high antennae should be used to provide improved service. (2) Maximum power. The maximum effective radiated power to be authorized on the respective channels is set forth in the following table: Maximum effective radiated power (in db above 1 kw) 20 db/500 ft. ant. 23 db/500 ft. ant. 23 db/500 ft. ant. 144. No one has objected to the Commission's proposal to establish only one class of station and to permit any station to operate on any channel, consistent with the Rules and standards. Some comments have been received with respect to operation with lower powers where the minimum mileage separations provided for in the Rules cannot be met. These comments have been considered above in another portion of this Report and the requests have been denied for the reasons set forth. The Commission is, therefore, finalizing its proposal to have only one class of station. 145. No comments were received with respect to the Commission's proposal concerning minimum power. Generally, we believe we should adhere to the proposal made in the Third Notice. It is a fact, however, that with very low effective radiated powers the service areas of television stations are extremely limited. Accordingly, we have provided in our Rules that no television station shall in any case operate with less than 1 kw effective radiated power. As so modified the proposal in the Third Notice with respect to minimum power is adopted. 146. Several comments have been received relating to the Commission's proposal with respect to maximum power for television stations. Radio Kentucky, Inc., and Radio Virginia, Inc., both oppose the granting of further power in the VHF above the maximum presently provided for in the Rules. The reason for this position appears to be a desire not to increase the disparity of coverage between the VHF and UHF. Havens and Martin opposes this proposal to limit power and subscribes to the Commission's proposal for an increase in existing power limits in the VHF. A. Earl Cullum's comment refers to his testimony relating power to frequencies in order to obtain comparable coverage. The frequencies involved on Channels 7 through 13 are approximately three times the frequencies involved on Channels 2 through 6, and the UHF channels allocated to television are approximately three times the frequencies on Channels 7 through 13. Cullum contends that in both of these cases the maximum power for the higher channels should be three times that of the lower channels and that putting a limit of 200 kw (23 dbk)33 on the power to be used on Channels 7 through 13, and 14 through 83 is unfair to those who wish to use these channels in competition with assignments made on Channels 2 through 6. James C. McNary filed a comment in which he stated that an amplifier tube with 25 kw was feasible on the UHF. Such a tube it was stated would provide a radiated power of 400 kw (26 dbk). McNary. therefore, recommends that provision be made for the use, on an individual basis, of power in excess of 23 dbk on Channels 14 through 83. Pacific Video Pioneers also proposes that the maximum power limitation of 23 dbk (200 kw) on Channels 14-83 be liberalized to permit single stations to increase to 26 dbk (400 kw) on a showing that objectionable interference will not be caused to other assignments using 23 dbk (200 kw) at 500 feet and to permit horizontal increases in power by two or more stations. On the other hand, RCA-NBC, and Communications Measurements Laboratories, Inc., support the Commission's proposal. 147. On the basis of the record it appears that the Grade B coverage of the television channels decreases as the frequency involved increases. Considering first the power relationship between Channels 2-6 and Channels 7-13 the propagation charts in the record establish that, assuming operation at 500 feet and the maximum powers proposed in the Third Notice, the Grade A service extends to 33 miles on Channels 7-13 as compared to 27 miles on Channels 2-6.34 However, in the case of Grade B service and where the only limiting factor is noise the service on Channels 2-6 extends 57 miles compared to 50 miles on Channels 7-13, based on the same powers and antenna heights. In view of this disparity with respect to Grade B service there was considerable testimony in the record favoring a three-fold differential in power between Channels 2-6 and Channels 7-13 rather than the powers proposed by the Commission. 148. The arguments described above are somewhat misleading since the prediction of service areas is made in all cases on the basis of noise limitations only. Cochannel operation is, however, a substantial factor in the determination of the effects of permitting an increase in power such as is requested here by the parties. For example, at 170 mils station spacing, with maximum power as specified under the Third Notice and 500 feet antenna height, the Grade B service of a station operating on Channels 2-6 or 7-13 would extend 41 miles and 47.5 miles, respectively, in the direction of a co-channel station. These coverages are related to the station separation and would be unchanged by the same increase in power of 34 See in this connection our discussion above of the manner of prediction of service areas and interference. BROADCASTING • Telecasting April 14, 1952 Part II Final TV Report • Page 15