Federal Communications Commission Record FCC 87-27

2 FCC Red Vol.5 Federal Communications Commission Record FCC 87-27

the AM band limit the opportunities for such changes Before the without creating objectionable interference. MQreovel. Federal Communications Commission these conventional methods do not always provide sta- Washington D.C. 20554 tions with sufficient economic flexibility to improve their service to all areas. The use of additional transmitters that simultaneously broadcast the programs of a primary origi- nating station is an effective and economical method that MM Docket No. 87-6 could be applied in some circumstances to improve and extend a station's service area. In the Matter of 4. The technology relating to synchronized transmitters was discussed early in the United States in a paper written Amendment of Part 7 by Charles B. Aiken of Bell Telephone Laboratories in i933, In 1937. the first experimental authorization to to Authorize the use of explore this technology in the U.S. was granted to radio Multiple. Synchronous station WLLH. Lawrence. Massachusetts. which has con- Transmitters by AM tinued its synchronous operations to this day. Similar Broadcast Stations experiments have been conducted in Boston (WBZ). Charlotte. North Carolina (WBT). Cincinnati. Ohio (WSAI). and in Washington. D.C. (WINX and WWDC). NOTICE OF INQUIRY Synchronized groups of transmitters have been used in the AM band on a large scale in Europe for many years. Adopted January 15, 1987; ReIeased March 3, 1987 and more recently in Japan. These foreign operations have been based upon the same theoretical bases as the By the Commission: earlier Uniied States operations.4 The results of the international experience have been largely consiStent with those obtained in the United States. These operations have I. INTRODUCTION further demonstrated the feasibility of synchronous operations and have confirmed earlier predictions of perfor- 1. This action initiates a J'otice of Inquiry (Inquiry into ) mance to be expected from different system designs. the use of multiple. synchronous transmitters to enhance and extend the signal coverage of AM broadcast stations. 5. There are numerous examples where such In April 1986. the Commission released the Mass Media applications could be made. For instance, additional Bureau's Report on the Status of i/ic AM Broadcast Rules. transmitters simultaneously broadcasting thc programs of RM-5532. (Report ).' The Report discussed. among other a primary station could he located in or near the areas things. the use of multiple transmitters. Of the various where service improvements are desired. Such service uses of multiple transmitters discussed, the application of enhancements could be instituted along major highways "synchronous transmitters" has prompted the most inter- in order to permit a station to serve the traveling public est as a means of providing immediate benefits. Thus, this over long distances forming 'ribbons of service." Addi- proceeding will initially focus only on issues primarily tional transmitters also could he located in nearby com- related to the use of synchronous transmitters. Synchro- munities lacking sufficient population to support their nous transmitter systems involve the use of two 01. more own independent stations. Other uses could include use broadcasting transmitters on the same frequency in neal of low power transmitters within a stations predicted geographical proximity. broadcasting the same program service area at locations suffering from inferior service material. They employ precision carrier frequency and because of anomalous propagation conditions or to pro- phase control in order to minimize mutual interference. vide service in nulls of directional antenna patterns. Other uses ot multiple transmitters will he considered in 6. Although three distinct uses of multiple transmitters other rule making actions where appropriate. were discussed in the Report, synchronous operation stim- 2. Although there has been much interest expressed ulated the greatest interest, as revealed in the comments regarding the use of synchronous networks, the Commis- that were filed in response to the Report. The comments sion has concluded that ii is necessary to develop a more gave general support to the suggested use of multiple complete record on the several related technical and transmitters for improvement or extension of AM service non-technical issues before proposing specific rules. In areas. The commenters were encouraged by the prospect addition to this Inquiry, the Commission has encouraged for coverage enhancement that synchronous techniques applications for experimental authorizations to develop may offer. Other commenters to the Report recognized technical data.2 Additionally, the Federal Communica- the need for careful study and the value of experimenta- tions Commission Radio Advisory Committee is encour- tion. CBS Inc. and Association for Broadcast Engineering aged to study these issues and to report its Standards Inc (ABES). however, expressed concern that recommendations to the Commission. such uses might increase the overall level of interference in the AM frequency band. Although ABES agreed with the Report's suggested methods of minimizing mutual II. BACKGROUND interference within synchronous transmitter networks, it added that synchronous operations would offer only mar- 3. Conventional methods for enhancing and extending ginal improvement in the coverage of some stations. the service area of an AM broadcast station typically called for increasing the transmitter power, designing a directional antenna system to improve service in a desired direction, relocating the station, or any combination of these. However, the crowded conditions that now exist in

I 2O FCC 87-27 Federal Communications Commission Record 2 FCC Rcd VoL 5

III. DISCUSSION hours, it may be feasible during the daytime hours for 7. There are both technical and non-technical issues on each transmitter to broadcast separate programming. de- which data and information are needed in order to estab- pending on the transmitters' proximity to each other. lish bases for specific rule proposals for the operation of 12. When phase synchronization is employed, there is synchronous transmitters. Of particular importance are no relative carrier frequency variation between the dif- issues pertaining to criteria used to define mutual inter- ferent transmitters, and the pattern of mutual-interference ference between transmitters in a synchronized network. remains fixed in time and place. Such interference would Of equal importance are the interference protection cri- not be very noticable on automobile receivers since auto- teria to be applied between synchronous networks and mobiles in motion would normally move quickly through stations outside of the synchronous systems. any areas of interference. For AM radios with ferrite rod 8. With respect to non-technical issues, the Commission antennas (virtually all modern table models and portable is of the view that restrictions on the use of synchronous radios), the effect of the stable pattern of interference can transmitters should be minimized to the extent possible. be greatly reduced by orienting the radio to improve the in order to maximize opportunities for innovation and signal strength received from one of the transmitters. service improvements to the public. Non-technical mat- 13. A difference among the carrier frequencies of the ters of importance include Ownership and licensing issues. transmitters in the group results in a variation in the total These are discussed in detail below. received signal at any point in the common service area over time. If the frequency difference is small enough (On Technical issues the order of 0.1 Hz). the variation can be compensated for 9. Previous experiences, both in the United States and by the automatic gain control (AGC) circuitry of the abroad, have demonstrated that there are areas of concern receiver and the listener will not notice significant distoi- in synchronous transmitter operation. While advance- tion. except at locations where the signals from the dif- ments in fixed point-to-point communication techniques ferent transmitters are nearly the same field strength. At made since the earlier experiments will solve some of the these latter points, the variation may exceed the dynamic earlier program distribution problems. e. g.. radio or land range of the AGC and distortion effects similar to slow line signal propagation delay. a principal consideration of fading will be experienced. synchronous operation is that of the zones of mutual- 14. The relative merits of these methods need to he interference. This interference occurs most prominently studied, Is there a significant advantage of one technique in the service areas of the synchronized transmitters at over the other or should the Commission establish rules locations where the signal levels from two or more syn- for both? Where possible. those stations operating under chronized transmitters are nearly equal. AM radio receiv- experimental authorizations with synchronous transmit- ers located in these interference zones may experience ters are encouraged to develop data on this issue. program signal fading or distortion, depending on the 15. Projection rajios for synchronized !ransniiuers. The method of transmitter synchronization employed. The term protection ratio" generally refers to the minimum boundaries of these zones or areas of interference as well ratio of the field strength of a desired signal to the field as the nature of that interference are dependent upon the strength of an interfering signal. in order to define the system design of a group of synchronous transmitters. existence of interference, in the case of synchronized 10. The interference can he controlled through geo- network, such a ratio is applied in determining the zones graphically spacing the synchronous transmitters or by of mutual interference that occur within the synchronized locating them in such a way as to cause the areas of system.5 In order to facilitate establishment of an appro- mutual interference to occur at locations where there are priate protection ratio for synchronous Operations. we few listeners. The effects of mutual interference can he encourage present and prospective experimental licensees further minimized through the equalization of modula- to investigate the values of the signal-to-interference ratio tion delay among transmitters.5 and through the use of applicable to reception of transmissions from synchro- phase rather than frequency synchronization. At nighL nized transmitter groups comprised of two or more trans- however, these zones of interference may be less signifi- mitters, taking into account alternative frequency cant. because skywave interference received from trans- tolerances. Both phase and. frequency methods of synchro- Initters within the group or from co-channel stations nization should be. considered..A European study .s.ug- outside the synchronized group could have a gleater effect gested one. .ap.prach . o.... .r.i.ningJhe...'prptctioio. uponservice. . ' ' ... This appioach involves the use of a statistical method based .:.Ofl ,st,i.bjctive. inpg; imp,resso ...c.recpt;ion Intra - system interference considerations quality, from a:transmitter.in a. synchronized. group. The results are then compared with. reception.., quality of. a 11. Synclzroni2aiion Techniques. Synchronization can be single achieved through either frequency synchronization or non-synchronized transmitter station.9 The EBU phase synchronization. The former is accomplished by Report cited an instance in which protection ratio values closely aligning the carrier frequencies (to 0.1 Hz or for nonfading signals were first determined under labora- tory conditions. For fading signals. however, only Opel'- better), and the latter is accomplished by phase locking ational tests using the transmitters together through the use of a control a synchronized network were conducted. circuit. The earlier experimental operations. previously referred to, tested both forms of synchronization. The 16. There are several factors to heconsidered in deter- experiments for phase synchronization employed trans- mining the protection ratio. These factors include: dif- mitters called "boosters" or "synchronous amplifiers. ference of transit time, frequency tolerance, whether the Where synchronization is only required during nighttime interfering signals are groundwave or skywave. and the effects of stereo and other audio processing techniques. Thcre are also subjective factors to consider. For instance.

1390 2 FCC Rd Vol.5 Federal Communkations Commission kecord FCC 87-27 speech and some forms of contemporary music may ap- be evaluated. A decision in this area could affect the pear less susceptible to distortion than other program amount of power permitted for each transmitter in a formats. synchronous group. 17. When three or more transmitters are used in a synchronous network, the problem of mutual interference Non - technical Issues is compounded. In such cases the combined effects of 22. Beyond the technical issues discussed above, we also miltiple interfering signals during nighttime hours must solicit comment on various non-technical policy isues he considered. For non-synchronized transmitters, this is related to the use of synchronous group transmitters. accomplished by calculating the root-sum-square (RSS) of These non-technical issues can be divided into two major the interfering signals. The EBU report, referenced above. categories -- (1) licensing and eligibility requirements, and states that in most cases where the desired signal is the (2) ownership restrictions. groundwave and the interfering signals are skywave. the 23. Licensing and EligthiUty Requirements. There are interference protection ratio is defined as the ratio of the three areas of concern regarding the substantive require- field strength of the wanted signal to the median value of ments and applications procedures that should be utilized the interfering field strengths. They also suggest. however, in authorizing synchronous transmitters. FirsL we request that the time probability of interference will lessen with that commenters address the question of what criteria the use of several synchronous transmitters within a net- should he utilized in deciding whether a synchronous work. We invite comments on the treatment of multiple transmitter should be authorized. For example, would a interfering signals within a synchronized network. Addi- synchronous transmitter be appropriate only in situations tionally. where experimentally possible. tests should be where a conventional AM station would be precluded? conducted on the effects of two as compared with three or Such preclusion could occur if a proposed new AM more synchronized transmitters. Results of such tests Station would cause prohibited overlap to other AM sta- should be rported in the comments. tions in violation of Section 73.37(a) of the Commission's 18. Transit time. Transit time is the signal propagation Rules or would cause nighttime interference in violation time interval from the transmitter to the receivei. It is of Section 73.182. Additionally. would the mere desire of dependent on the location of the receiver, and may vary a licensee to increase coverage in one or more directions in the case of nighttime ionospheric propagation. if the be sufficient justification to permit synchronous opera- difference in transit time from several sources is negli- tion? gible and the distribution delay is equalized, theoretically 24. Although synchronous transmitters may be used to there should be no distortion, but this occurs in practice enhance or extend the coverage areas of AM stations, for only a very small geographical area. Comment is should there be any limits ihposed on the extent to requested on the effects of transit time and the manner in which the coverage area of an AM station may be aug- which program distribution equalization can be employed mented by the use of synchronous transmitters. and if so, to minimize these effects. what should they be? Alternatively, should synchronous 19. Transmiuer Power. Much of the experience from operation be permitted only within an AM station's pro- experimental synchronized operations previously gained tected contour under the Commission's Rules? We solicit within the United States employed relatively low powered comments on these questions and other matters related synchronized transmitters. As shown in the EBU report. thereto. however, this is not necessarily an inherent requirement 25. Second, we invite comment on who may be licensed for synchronous operation. Comments are requested as to to operate synchronous transmitters. Because these trans- whether the power of synchronized transmitters should he mitters may cause interference to the signal of the pi'i- restricted or whether power levels up to that permitted mary AM station that is being rebroadcast or to other for the station class of the primary statioO should be synchronous transmitters within the same network, we allowed, consistent with requisite protection to other sta- are not inclined to authorize their use by any party other tions. than the AM station licensee who seeks to expand its service area. Moreover, such a licensing limitation is Inter - system interference considerations consistent .with the requirement that FM boosters--which 20. Additional important issues upon which comment rebroadcast the programing of a parent FM station on the is desired concei'n the interference protection criteria that same carrier frequency as the parent station-he autho- would be applied between synchronized networks and rized only to the licensee or permittee of the parent stations not in the synchronized network. With respect to station)0 Since synchronous transmitters, like FM boost- groundwave interference protection criteria, it appeal's ers. operate on the same frequency as the parent station that the groundwave signal overlap restrictions specified and pose a potential for interference to the primary in Section 73.37(a) of the Rules may be appropriate. The station. we believe that a similar licensing limitation matter of skywave interference protection criteria, how- would be appropriate. ever, is not as clear. One such issue concerns the manner 2o. Third, we question how requests or applications for in which transmitters in the synchronized network should synchronous transmitters should be processed. Our initial be protected from skywave interference caused by stations view is that such applications should be processed like not in the synchronized network. applications for major or minor changes in AM broadcast 21. Similarly, another issue is whether the nighttime facilities because synchronous transmitters are intended to skywave interfering signals from the transmitters in a be permanent and protected improvements to the cov- synchronized network should be considered individually erage of existing AM stations. Consequently. if an applica- or whether the cumulative interference effect of the entire tion for a synchronous transmitter is processed like a synchronous group should be considered when calculat- major change, it would be placed on a cut-off list and ing skywave interference to other stations on the channel. could not be acted upon by the Commission until after a In this regard the effect of the 50% exclusion rule must 30-day public notice period. During that time. the public

l11 FCC 87-27 Federal Communications Commission Record 2 FCC Red Vol.5

would be afforded an opportunity to file petitions to deny stances of contour overlap between synchronize transmit- pursuant to Section 309(d) of the Communications Act ters and other comrnonl owned AM stations that are not and Section 73.3584 of the Commission's Rules. In addi- part of the same synchronous network. tion. any applications for changes in existing AM facilities 2. Another local ownership restriction is the or for new AM stations which may be mutually exclusive 'one-to-a-market" rule which, inter alia, prohibits the with a synchronous transmitter proposal would have to be common ownership of commerciaL AM and television filed during this 30-day period)' Such mutually exclusive stations in the same market. Specifically, the rule achieves applications generaib,' warrant a comparative hearing to this result by barring cross-ownership whei'e either the 2 select a permittee under the As/ibacker doctrine:12 I-low- mV/rn groundwave contour of the AM station encom- ever, if a request for a synchronous transmitter were passes the entire community of license of the television processed like a minor change in facilities, it could be station, or where the predicted Grade A contour of the gianLed without the necessity of being placed on a cut-off television station encompasses the entire community of list: and only those informal objections filed prior to license of the AM station." We bel'reve that it would he grant could he considered. Accordingly. we request com- inappropriate to apply this cross-ownership restriction, to ment on whether such a cut-off list approach should he synchronous transmitters as this would also hamper the utilized or under what circumstances requests for syn- development of this technology. Moreover, exempting chronous transmitters should he considered as minor synchronous transmitters from this rule would give AM changes. Alternatively, we question whether synchronous broadcasters greater flexibility in using this technology to transmitters should he treated as secondary to full-service enhance and expand their service areas since they would stations and be afforded no continuing protection. not have to he concerned with contour encompassment 27. Ownership Restrictions. Next, we must consider between ,commonly owned television stations anti AM whether owneiship restrictions should apply to synchro- synchronous transmitters. Accordingly. we solicit com- nous group transmitters on either a local or a national ment on whether the public interes) would be served by basis. Such restrictions currently apply to the commercial exempting synchronous transmitters from the "duopoly' AM. FM. and television services. With respect to national and 'oneto-a-ma,'ket" rules. ownership restrictions, the Commission generally permits an individual to have a cognizable ownership interest in a maximum of 12 commercial AM stations.' The ques- IV. CONcLUSION tion arises as to whether synchronous transmitters, addi- 30. Synchronous transmitter systems have been success- tional to the primary station, should he counted for fully used in Europe for many years to extend service. purposes of this 'rule of 12.' Our preliminary view is Although conditions in the United States differ, such that synchrohobs transmitters shouki not he attributed operations appear to offer advantages here as well. Inter- under this rule. We base this position on two reasons. nationally. general standards fo,' synchronous transmitter First, we believe that such a restriction may not allow for systems already exist, hut standards specifically tailored the full development of this proposed new broadcast for the U.S. need to be developed. Moreover, non- technique and the benefits that it may afford. If broad- technical issues unique to the U.S. need to he resolved casters are limited to owning a total of 12 commercial before synchronized networks can he routinely autho- AM stations, including synchronous transmitters, then rized. they might he discouraged from building many synchro- 31. The primary issues addressed in this Inquir,v are nous transmitters because it could affect the number of summarized as follows: additional AM stations that they could acquire. Second. exempting synchronous transmitters from the national ownership restrictions would be consistent with Commis- What technical standards should be adopted govern- sion precedent. in this regard. the Commission does not ing the operation of a synchronous group of trans- count terrestrial satellite television stations for purposes of mitters as it affects intra-system interference and the twelve-station i'Wc. Like synchronous transmitters. other system impairments. these satellite television stations repeat most, if not all, the What interference protection criteria should be ap- pràgramming from a parent station'and can have broad- plied between synchronous networks and individual cast facilitie comparable in power and coverage to the stations not in the synchronous network paient station Accoidingl we solicit comment on whether:we should take .the same approach for synchro-• What level of distortion can be anticipated as a result of using frequenço . phase synchronization flOU5:trnSrflittClS; ..::::...... ,. ., ...... techniques and which synchronization technique is 28. W also .jf to cOnside whéthëf JodalO*nership more adyantageous? . . i'eti'ictions should apply to synchronous group transmitters. One such restriction is the AM 'duopoiy" rule Would the utility of nighttime synchronous trans- which currently prohibits overlap between the I mV/rn mitter operations be diminished significantly be- contours of commonly owned commercial AM stations.'5 cause of skywave interference? Clearly. the 'duopoly" rule should not apply to overlap What treatment should synchronous transmitters be occuring within a synchronous network. Such local own- afforded under the multiple ownership rules and ership restrictions would have the detrimental effect of what licensing criteria should be applied? unnecessarily inhibiting the development of this new technology and preventing the enhancement or expansion 32. In order to assemble a comprehensive record, we of service by AM broadcasters. For similar reasons. we invite comment from all interested parties on the issues also believe the "duopoly" rule should not prohibit in- discussed in this Inquiry. We also encourage experimental licensees to submit their results or observations relating to the technological concerns raised in this Inquiry. If corn-

1392 2 FCC Red Vol. Federal Communications Commission Record FCC 87-27 menters wish to address issues we have not identified, we Sec Bell Telephone System technical publication. A Study encourage them to do so. The record established in this Of Reception From Synchronized Broadcast Stations.t by proceeding will allow the Commission to analyze the Charles B. Aiken. Bell Telephone Laboratorie5. published in impact of synchronous group transmitters on the delivery Proceedings of the Institute of Radio Engineers, Vol. 21, pp. of AM service to the general public, and to develop rule 1265-1301, September. 1933. proposals. ' See European Broadcasting Union (EBU) Technical Report 33. Pursuant to applicable procedures set forth in Sec- 3210, August 1974. 'Synchronizei1 Groups of Transmitters in tions 1.415, and 1.419 of the Commission's Rules, inter- LF and MF Broadcasting." which includes examples of low to ested parties may file comments on or before May 4, 1987 high powered synchronous transmitters and techniques of fre- and reply comments on or before June 3, 1987. All quency control. etc. relevant and timely comments will be considered by the Modulation delay, in thi5 case, is the amount of time that Commission before final action is taken in this proceed- the program signal is delayed in being processed onto the ing. To file formally in this proceeding participants must carrier frequency. file an original and five copies of all comments, reply The control could be accomplished in any of several ways. comments and supporting comments. If participants want including for example. the use of digital techniques employed each Commissioner to receive a personal copy of their via a microwave radio link. comments. an original and nine copies must be filed. See the British Broadcasting Corporation. Research Depart- Comments and reply comments should be sent to Office ment Report. February 1976, "Reduction of mush-area distor- of the Secretary, Federal Communications Commission. tion in common-frequency M.F. transmitter networks." Washington. D.C. 20554. Comments and reply comments The current international protection ratio for synchronous will be available for public inspection during regular business hours in the Dockets Reference Room (Rm. 239) operation used in international Agreements applicable to the of the Federal Communications Commission. 1919 M U.S. is 8 dB. See Final ActS of the Regional Administrative MF Street. N.W., Washington. D.C. 20554. Broadcasting Conference (Region 2). 1981 and Agreements between the U.S. and Canada. and Mexico. respectively signed in 1984 and 1980. ' V. AUTHORITY See CCIR Document Recommendation 500-I listing EBU 34. Authority for issuance of this Notice is contained in reports on synchronized transmitter networks from the United Sections 4(i). 303(r) and 403 of the communications Act Kingdom. India, and Japan. It) of 1934. as amended. Sec 47 C.F.R. Section 74.1232(e) (1985). 35. For information concerning this proceeding contact A mutually exclusive situation arises whenever two or Bernard Gorden at (202) 632-9660 or Andrew 3. Rhodes more bona fide applicants timely file for use of the same (Legal) at (202) 632-7792. broadcast frequency. or for different frequencies whose use would be technically incompatible under the Commissions FEDERAL COMMUNICATIONS COMMISSION Rules. 12 See Ashbacker Radio Corp. v. FCC. 326 U.S. 327. 333 (1945). 13 An individual generally has an attributable interest in a broadcast station if the individual is an officer, director, general William .1. Tricarico partner, or owner of 5% or more of the voting stock of the Secretary station. See 47 C.F.R. Section 73.3555. Notes I and 2 (1985). ' Sec 47 C.F.R. Section 73.3555(d)(L) (1985). This limit may be increased to 14 AM stations provided that the additional two FOOTNOTES stations are controlled 50% or more by members of minority The Report (pp. 71-77) included a discussion on the follow- groups as set forth in 47 C.F.R. Section 73.3555(d)(3) (1985). ing three types of multiple transmitters: (1) synchronous opera- ' 47 C.FR. Section 73.3555(a)(1) (1985). We recently pro- tion, (2) AM satellite stations, and (3) AM/FM translators. posed to relax the radio 'duopoly" rule. See Notice of Proposed adopted 2 Since January 1986, the Commission has granted Rule Making in MM Dockei No. 87-7. FCC 87-28. experimental authorizations for the construction of synchro- January 15, 1987. nous systems to the following licensees: I(ROL of Henderson. 47 C.F.R. Section 73.3555(b)(I) (1985). In MM Docket No. Nevada; KOB of Albuquerque. New Mexico; KIPA of Hilo. 87-7, we have also proposed to modify the scope of the radio- Hawaii; and WiNO of West Palm Beach. Florida. Requests for television cross-ownership provisions of the 'one-to-a-market' experimental authorizations for synchronous transmilter oper- rule. See note 15, supra. ations are currently pending from the following stations: KGNW of Seattle, Washington; KNEW of Oakland. California: KNIJZ of Houston, Texas; and WORC of Worcester. Massachu- setts. Experimental authorizations are on a secondary basis and are not afforded interference protection from other existing or future primary station assignments. Such authorizations also require that the permittees file comments to this Inquiry and detailed progress reports on their experimental operations.