Last week, the FCC released the full text of Notice of Proposed Rule Making (NPRM) to set rules for DTV translators, LPTV stations and boosters. The 63 page NPRM has more detail on proposed rules than the summary of the NPRM covered in my August 11 RF Report on FCC's August 6 meeting.
The FCC asked if DTV translators should be allowed to rebroadcast multiple video program streams from different DTV broadcast stations on one output channel, provided arrangements are made with the primary DTV stations. While this could reduce the availability of HDTV signals, it could give viewers access to the programming of more stations. For this to happen, it is likely the translator operator would have to modify the DTV broadcast signal, changing its video format or dropping ancillary and supplementary services. The NPRM requests comment on whether translator operators should be allowed to change format and drop services after receiving permission from the primary DTV broadcaster. If subscription services are carried, should the translator operators be allowed to provide these "for the sole purpose of funding the operation and maintenance of translator systems?" The commission also proposed allowing DTV translators to receive DTV input signals using any of the methods allowed for analog translators, including microwave. With the current congestion in broadcast microwave spectrum, is such use of broadcast auxiliary spectrum practical?
The NPRM proposes allowing digital LPTV stations to "use their bit stream dynamically to transmit one or more digital programs in any DTV video format," as well as ancillary and supplemental services and subscription services.
The NPRM asked for comment on whether the FCC should prefer the use of regenerative DTV translators, which process the signal to reduce errors and improve quality, over heterodyne translators, which simply convert the incoming signal to another channel and amplify it with no digital processing. Recognizing that "spectrum availability presents a great challenge to the digital conversion of TV translator and LPTV stations," the FCC has proposed making Channels 2-59 (excluding channel 37) available for digital LPTV and translator stations. As secondary stations, the stations would be required to operate so as not to interfere with primary users of the spectrum and to protect earlier authorized secondary users. Comment was requested on whether there should be special requirements for using Channels 52-59, including a demonstration that no lower channels are available. If there are special requirements, should they be applied equally to applications for new digital LPTV/translator stations and applications seeking to convert an existing analog operation to digital?
Protected service contours have already been defined for Class A digital TV stations -- 43-dBu for Channels 2-6, 48-dBu for Channels 7-13 and 51-dBu for Channels 14-51. These values were chosen to yield digital service areas comparable to the Class A stations' analog service areas. The NPRM proposes using the same contours for digital LPTV and translator stations. The 51-dBu contour would be used for all UHF channels, including 52-69.
The NPRM devotes almost 13 pages to interference protection methodology. The NPRM begins the discussion stating, "With limited TV channel availability throughout much of the country, we wish to explore every means of maximizing channel use for digital LPTV and translator service. In so doing, we must also consider the interference protection rights of others, both full power and low power stations. A hallmark of the low power television service in its 20-year history has been the few reported cases of interference caused by LPTV and TV translator stations. We seek comment on protection standards and methods that will permit digital service opportunities and provide adequate safeguards against interference."
In most cases, the FCC proposes adopting existing desired to undesired (D/U) ratios in Section 73.623(c) used for full-power DTV stations. The NPRM proposes uses first adjacent channel ratios in Section 73.623(c)(2), but requested comment on whether alternative proposals, such as the one from Gary Sgrignoli proposing "simple" and "stringent" emission masks for digital TV translators, should be considered. DTV translators using the less restrictive emission masks would be subject to more restrictive adjacent channel D/U ratios. The NPRM asks commenters to consider the processing implications of multiple emission masks and related D/U ratios.
Although contours are the standard method for determining analog LPTV and translator interference protection, the FCC has allowed the use of waivers based on Longley-Rice and OET-69 methods. For digital LPTV/translator stations, the NPRM states, "The DTV methods provide more comprehensive, accurate and realistic analyses than the contour protection method currently used for the LPTV service. Given these advantages and the DTV model's wide-spread use, we are inclined to prefer the DTV methodology over the contour protection method as the basis for accepting digital LPTV and TV translator applications. Alternatively, should we continue to use the contour protection method with allowance for Longley-Rice and OET 69-type methods on a waiver basis? Are there other methods we should consider (e.g., a contour protection method using the Longley-Rice propagation model)?"
The NPRM recognizes a limitation in the OET-69 methodology -- the use of a standard elevation pattern for the antenna rather than the actual elevation pattern of the antenna. Because LPTV and TV translator stations typically use lower gain antennas with wider elevation patterns and greater beam tilt, use of the OET-69 elevation pattern could result in the actual signal strength of the LPTV/translator signal being much stronger than what was predicted using the standard elevation pattern. In other cases, if the LPTV/translator is located on a high elevation site some distance from the community it serves, an OET-69 using the default antenna elevation pattern may substantially under predict signal level in areas it serves and deny those areas protection from interference by other stations. The NPRM said that incorporating antenna beam tilt into the LPTV implementation of OET-69 would help alleviate this concern and asked for comment on whether this was needed.
The Notice also asked whether precise frequency control should be required for digital LPTV/translators operating one channel above NTSC stations (full or low power): "Considering the lower power levels of stations in the LPTV service, is there a need to apply this requirement among digital and lower 1st adjacent channel analog LPTV and TV translator stations within some geographic proximity?" To make maximum use of available spectrum, the FCC sought comment "on other changes to our LPTV service interference protection rules that could provide additional spectrum opportunities without unduly risking impermissible interference. For example, should we require all analog LPTV and TV translator stations to operate with a frequency offset?"
Power levels for digital LPTV/translator stations are also addressed. The FCC previously set limits of 300 W digital ERP (average) for Channels 2-13 and 15 kW for Channels 14-69. The NPRM asks if these power levels are appropriate for covering the areas served by analog LPTV/translator stations. "If not, how should the limits be changed and on what basis?"
The summary above does not include all the topics discussed in the 63 page Notice of Proposed Rule Making (FCC-03-198). The NPRM discusses almost every rule related to analog LPTV/translator stations, both technical and operational, and how they should be applied to digital LPTV/translator stations. In addition to the items above, the NPRM addresses unattended operation, station identification, modification of transmission systems, equipment standards for technical quality and interference avoidance and out-of-channel emission limits. There is also a discussion of proposed rules for digital booster stations. These rules will impact all TV broadcasters, whether or not they use low power DTV stations or translators. Take time to read through the NPRM. Comments are due 60 days after publication in the Federal Register, with reply comments due 30 days after that.