RF CURRENT
Welcome to RF Current, a weekly electronic newsletter focusing on Broadcast
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Issues are dated each Monday, although recently I've needed an extra day or
two to complete each issue. Articles may be posted earlier if time permits or
if there is a major, breaking story.
<<< Back to March 6 - Issue 204
March 13, 2000 - Issue 205 Final Edition
- INDUSTRY - Itelco Launches COFDM Transmitter Components for U.S. Market (Mar. 13)
- It appears Itelco decided not to wait for the debate between 8-VSB and COFDM DTV modulation methods to be settled before launching what it called "the industry's first COFDM exciter modulator for the North American market." Howard McClure, Vice President for North America at Itelco, said, ""Itelco does not take sides in the controversy over 8VSB versus COFDM currently raging in the United States. This product release is intended to meet the requirements of our customers, not to endorse COFDM modulation for an American digital TV standard."
Itelco offers COFDM transmitters in power levels from 1 W to 100 kW. The North American unit is a 6 MHz version of Itelco's European 7 and 8 MHz DVB-T exciters. Itelco said it could provide an automatic changeover unit to allow switching between its 8-VSB and COFDM exciter modulators via remote control. This would be useful for field testing.
This information was from an Itelco press release Itelco Launches COFDM Transmitter Components for the U.S. Market - Move Likely to Re-Ignite Debate Over Digital TV Standards.
- SCIENCE - Adelaide University Physicist Predicts Damage from Solar Storms (Mar. 10)
- Dr. Roger Clay, a physicist at Adelaide University (Australia) warned that power grids and satellites may be damaged in solar storms as we pass through this period of maximum solar activity. He said that the February 18 coronal mass ejection (CME) of high-energy particles did not cause as much damage as some had feared, but warned that this was likely the first of many CME events over the next two to three years.
Dr. Clay explained, "If the next solar storm is no worse than the one last month, then there's no problem. But of course, since the last solar maximum 11 years ago, we've got a lot more satellites and we depend a lot more on satellites. All our communication satellites, our GPS systems and these sort of satellite systems have computer chips in them. The computer chips are susceptible to these particles going through them because they deposit electrons in there, and that's enough to change a zero to a one in the computer memory, which could effectively disable the satellite."
The problems caused by a CME aren't limited to space. The solar discharge can disturb the Earth's magnetic field and induce large currents in wires on earth. Dr. Clay said, "If you've got a large loop of wire, and you've got a magnetic field going through it, a change in the magnetic field induces an electrical current through the wire." Referring to a large power outage in Canada during a previous solar maximum, Clay said, "There is a move to integrate power grids across countries so, as in many countries, what we have here in Australia, as we've been joining up grids between the states, are huge loops of line all connected together. When the Earth's magnetic field changes quite rapidly, it can induce big currents in the national grid, and those currents may overload the system. This is what happened in Canada,"
The energized particles have an effect on humans as well. Dr. Clay said this has to be considered when building orbiting space stations. "Roughly one person in one hundred per year in such an environment would die from this radiation."
More information on this topic is available in an Adelaide University Press Release.
- SATELLITE - New Technologies in Hughes-built ICO Global Communications Satellite (Mar. 9)
- ICO Global Communications F-1 Satellite, scheduled for launch March 12, will have some interesting technology on-board. The modified Hughes HS 601 satellite includes a unique, active phased-array antenna design and a digital beam-forming processor developed by Hughes Space and Communications. A Hughes Press Release said "this 'smart' processor, designed in the mid-1990s, is the most complex and capable ever flown on a commercial satellite." F-1 will be the first of twelve medium-earth-orbit satellites. The satellites will provide a direct S-band link to users and collectively will provide full earth coverage. The active antennas antennas and beam-forming processor allow each satellite to form multiple beams that can be adjusted to match varying usage patterns and maximize the use of available bandwidth as market demands change.
Hughes said the S-band antennas required the ICO version to be 25 percent taller than other HS 601 satellites. In addition, Hughes had to extend the thermal radiators on the satellite to dispate the extra heat from the added electronics. More information, including pictures of the satellite, are available in the Hughes Press Release.
- FCC Commences Periodic Review of DTV Conversion (Mar. 8)
- The FCC began its first periodic review of progress in the U.S. DTV conversion by issuing a Notice of Proposed Rule Making NPRM) - Review of the Commission's Rules and Policies Affecting the Conversion to Digital Television (Word document - fcc00083.doc). Areas of interest to broadcast engineers include a proposal to effectivaly increase the required DTV signal levels in the community of license, requirements for replication of current NTSC coverage, setting a date for stations to identify which of their two channels they intend to keep after the transition, DTV application processing procedures, the current status of the 8-VSB DTV transmission standard and minimum performance levels for DTV receivers. The FCC said it was not asking for comment on issues regarding the 2006 conversion target date, DTV broadcast carriage on cable systems, requests for reconsideration of already decided issues and channel allotment or change requests.
The FCC is concerned that some DTV stations may not provide adequate coverage over their principal community of license if the signal signal level in the community is close to the minimum currently required. At present, there is only one service level for DTV. That is the level based on the minimum required for reception, 41 dBu on UHF channels, under the ATSC planning factors. The FCC proposed raising the signal level required over the community of license by difference between the existing definitions for analog City Grade and B Grade coverage. This would result in DTV "City Grade" levels of 55 dBu for channels 2-6, 57 dBu for channels 7-13 and 57 dBu for channels 14-69. The FCC asked for comments on whether this requirement would be appropriate for DTV stations, whether it can be readily accomplished, whether the costs of adopting the proposals would outweigh the benefits, or whether an alternative minimum level of principal community service is justified.
In the NPRM, the FCC said "We believe it is important now to consider what requirements are appropriate for eventual replication so that stations can take account of these requirements as they plan and construct their DTV facilities. We seek comment on whether we should establish a replication requirement and, if so, how we should frame it, when it should become effective, and what consequences should follow for stations that fail to meet it." The FCC requested comment on whether the coverage requirement should be based on coverage contours or the OET-69 Longley-Rice propagation model. Should the coverage requirement be based on area or on population? An alternative to a replication requirement would be the implementation of a DTV principal community service requirement, as outlined above. The date for requiring compliance with a replication or coverage requirement was discussed in the NPRM, with the FCC stating "In order to allow stations a reasonable period to operate with smaller facilities, it seems appropriate to delay a replication requirement until at least May 1, 2004." While the FCC felt most stations would consider it in their best interests to replicate coverage, "Nonetheless, we propose that any station's failure to comply with the proposed replication rule would result in the loss of protection of the station's full-replication allotment facilities." Comments were requested on whether there should be additional consequences for failure to replicate coverage.
The FCC proposed setting a date not later than 2004 for stations with both their NTSC and DTV channels in the channel 2-51 core spectrum to identify which channel they intend to keep after the transition. This information is important for stations planning to maximize DTV facilities once analog broadcasting ends.
The FCC also requested comment on some DTV application processing procedures. Specifically, the FCC invited comment on "(1) whether to establish DTV application cut-off procedures; (2) how we should resolve conflicts between DTV applications to implement 'initial' allotments; and (3) the order of priority between DTV applications and NTSC applications." One of the methods suggested for reducing the number of mutually exclusive applications was the establishment of cut-off dates. Applications filed after the cut-off date would have to protect application filed before it. An option under this selection would be to consider applications as cut-off the day they are filed. Options for processing mutually exclusive (MX) applications include granting all applications where the interference was outside the stations' coverage protected in the allotment table, Another option would be to treat MX applications as new DTV applications. Applicants would be encouraged to mutually resolve the conflicts or face possible dismissal or spectrum auction. The FCC asked if a priority scheme similar to that specified the new Class A TV service legislation should be applied between NTSC and DTV stations. That legislation required Class A TV applicants to protect analog TV stations transmitting or change applications filed as of the enactment date of November 29, 1999. Also protected were the DTV service areas in the FCC's DTV Allotment Table and DTV stations seeking to maximize their service area, provided the FCC was notified of the station's intent to maximize by December 31, 1999 and applications are filed by May 1, 2000.
The NPRM opened a small window for reconsidering the 8-VSB modulation method adopted in the FCC's Fourth Report and Order on Advanced Television. In this NPRM, the FCC states, "While we continue to believe that NTSC service replication is achievable by DTV operations using the 8-VSB standard, we recognize that some in the industry have raised various issues with respect to that standard. For example, Sinclair Broadcasting Group filed a Petition for Expedited Rulemaking urging the Commission to modify its rules to permit the use of COFDM modulation in addition to the 8-VSB standard. Sinclair argued that the COFDM standard offered easier reception with simple antennas and would enable broadcasters to provide fixed, mobile and portable video services with greater capacity for technological improvement. We dismissed that petition, indicating that concerns about 8-VSB, such as those raised in the Petition, were better addressed in the context of this proceeding." In response to these issues, the FCC invited comment on the status of the 8-VSB DTV standard, saying "We are particularly interested in the progress being made to improve indoor DTV reception under the existing transmission standard and manufacturers' efforts to implement DTV design or chip improvements. We also ask the industry to submit information regarding any additional studies that may have been conducted regarding NTSC replication using the 8-VSB standard."
The NPRM noted that some broadcasters have recommended the FCC set receiver standards for DTV. In the NPRM, the FCC asked for comment on whether it had the authority to set minimum performance levels for DTV receivers. The NPRM reminded commenters, however, that "This issue was pleaded several years ago by various parties in response to the Commission?s Fourth and Fifth Further Notices of Proposed Rule Making in the DTV proceeding, and comments in this proceeding should take account of these earlier submissions. Second, we request comment on the desirability of adopting minimum performance levels. And, third, comments should address how these requirements should be structured, including timing considerations."
The FCC said, "Initial evidence indicates that stations are facing relatively few technical problems in building digital facilities." Three years into the five year period mandated for commercial TV stations to begin DTV transmission, the NPRM noted that a total of 1376 TV stations filed DTV construction permit applications, of these, 316 stations have been granted construction permits and 92 stations are on the air pursuant to those permits. Twenty-seven additional stations are on the air with special or experimental DTV authority. Stated another way, almost half way through the DTV conversion period for all TV stations, 81 percent of all TV stations have filed DTV applications, 23 percent of these stations have received construction permits and 29 percent of the stations that received construction permits are on the air. The number of stations on the air with special or experimental DTV authority is less than 2 percent of all DTV stations. Put another way, 50 percent of the way through the DTV conversion 7 percent of all U.S. TV stations are on the air, either licensed or under special/experimental authorization, with DTV.
A summary of the complete Review of the Commission's Rules and Policies Affecting the Conversion to Digital Television may be found in the FCC News Release FCC Commences Periodic Review of Digital Television Conversion.
- FCC Issues Order on Revision of Antenna Structure Rules (Mar. 8)
- The FCC issued a Memorandum Opinion and Order on Reconsideration in the Matter of Streamlining the Commission's Antenna Structure Clearance Procedure and Revision of Part 17 of the Commission's Rules Concerning Construction, Marking and Lighting of Antenna Structures (WT Docket 96-5. The MO&O addressed and resolved various filings concerning the FCC's antenna structure clearance procedures.
Some petitioners requested the FCC set an accuracy standard for the submission of antenna data. The Order said one of the petitioners, Teletech, " contends that by allowing an antenna structure owner to choose the means of measurement, the Commission's procedures allow owners to employ methods with negligible accuracy, such as counting distances by heel-to-toe footsteps from a known location or measuring height by the amount of time it takes a coin to fall from the top of an antenna structure." The FCC deferred specification of accuracy to the FAA, because applicants are required to provide proof of an FAA determination of "no hazard" before the FCC will grant an antenna structure. To clarify this, the FCC said it will not process a registration application in which the specified coordinates differ from those on the FAA determination by more than one second in latitude and longitude, or 0.3 meters (one foot) in height. By requiring that an applicant for an antenna structure registration submit a valid FAA determination of "no hazard" that is no more than one second and 0.3 meters different from the coordinates and height listed on the registration application, we promote the accuracy of our antenna structure registration database while recognizing deferring tothat the FAA isas the expert agency for air safety in determining the appropriate accuracy for how accurate antenna structure data must be."
In cases where the antenna structure owner and tenant licensee(s) are not able to agree on the correct coordinates for a sitek the FCC will allow the licensee to request a waiver of the requirement that the registration data and the application differ and ask the Wireless Bureau to review the situation. The MO&O said, "We emphasize that we consider this requested relief to be an extraordinary situation, and we will expect the licensee to fully describe the steps it has taken to negotiate with the owner and explain in detail why it will not or cannot agree with the coordinates the owner has used. In situations of irreconcilable disagreement between the structure owner and licensee, the licensee might find that the best solution is either to acquire ownership of the structure or to locate its facilities elsewhere."
Additional information on how the FCC will treat other situations is contained in the FCC Memorandum Opinion and Order on Reconsideration. (This document is in Adobe PDF format.
- DTV - SkyStream Networks Launches "End-to-end Solution for Delivery of Internet Content Over Broadcast Networks" (Mar. 7)
- SkyStream Networks announced its SkyStream 2000 edge media router (EMR) is now available. The product is designed to give broadcasters the ability to stream web content to consumers over broadcast networks such as digital TV or digital satellite. ISPs can use the EMR to delivery live Webcasts or other streaming media content without congesting the Internet backbone.
A system would consist of a SkyStream source media router (SMR) at the origination point of the streaming Internet content to be sent over broadcast networks. The SkyStream 2000 edge media routers receive the Internet content sent over the broadcast network by the SMR. The EMR sits on the the edge of the Internet and sends the streaming content to consumers using various last-mile technologies. The Skystream 2000 can handle data rates up to 60 Mbps.
This information was obtained from the Skystream Networks press release Skystream Networks Launches End-to-end Solution for Delivery of Internet Content Over Broadcast Networks.
- OTHER Items of Interest
>>>>Next March 20 - Issue 206
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