RF CURRENT



Welcome to RF Current, a weekly electronic newsletter focusing on Broadcast technical and F.C.C. related issues. This newsletter is part of The RF Page @ www.transmitter.com, a web site devoted to TV Broadcast RF engineering. For more information see the What is... guide to the R.F. Page site.

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 July 12 - Issue 173

July 19, 1999 - Issue 174 Final Edition

DTV - Sinclair Demonstrations Ignite COFDM vs 8-VSB Modulation Debate (July 19)
Recently Sinclair Broadcasting has been showing broadcasers and others demonstrations of COFDM and 8-VSB reception using indoor antennas in the Baltimore Maryland area. Both signals were transmitted at 50 kW average effective radiated power. The results? According to Sinclair engineers, the COFDM tranmissions could be easily received in locations where 8VSB signals were difficult, if not impossible, to receive on indoor antennas. Sinclair has not published a report on the tests, but one is expected before the IEEE Broadcast Technical Symposium in Washington DC in September.

ATSC issued a response to Sinclair tests, saying "The Sinclair position is unwarranted and irresponsible. It is unwarranted because a growing body of evidence supoorts the performance of the VSB transmission system, and there is no clear evidence that COFDM is better. It is irresponsible because it seriously understates the impact of a change." ATSC admitted there are problems and they can do better. The ATSC response asked "Is there a basis to give up on VSB?" The answer, from ATSC, is " Absolutely not. The best path is to continue to put our energy into improving and optimizing the overall VSB transmission system, to ensure the success of the DTV transition."

Sinclair has stated before that the issue is not COFDM versus 8VSB. The question is whether the 8VSB system, as currently implemented, will provide service into homes and offices that use indoor antennas. Based on their tests, the current 8VSB implementation did not work in the heavily populated urban areas. For another article on this, see the E-Town News article DTV: Set for an Early Grave? in Other Items below.

ATSC agreed that with regard to indoor reception, "While the data taken is promising, there is much work to do, and improvement is needed and expected." ATSC said "Some observed indoor reception problems can be tied to performance limitations of early DTV receivers. We are observing a substantial spread in performance of receivers, with some performing better than the benchmark Grand Alliance prototype, as anticipated, but others performing worse." In summary, ATSC said "We emphasize that there is no concrete information to suggest that COFDM indoor reception would be better. There is substantial information to show that VSB provides superior outdoor reception. We believe it will be shown that VSB provides superior indoor performance as well."

ATSC was also concerned that "Any decision to revisit the transmission standard would cause years of delay." ATSC cited the need for an extensive test program and a new spectrum use plan, "given the differences in performance between 8-VSB and COFDM." ATSC said "existing DTV transmitters and receivers would need to be modified, or would become obsolete."

COFDM is receiving significant support in Europe and equipment is becoming available for it. The ability to modify the transmission parameters to trade off data rate for a more robust signal is attractive to broadcasters looking beyond HDTV to data delivery and interactive TV. Look for a report on the status of COFDM and 8-VSB in the September 1999 TV Technology RF Column. More information is available from:
FCC Proposes Creation of Wireless Medical Telemetry Service (July 16)
Wireless medical telemetry devices currently operate on an unlicensed, secondary basis on TV channels 7 to 46 under Part 15 of the FCC Rules and on a secondary basis on unused frequencies in the 450-470 MHz band. Spectrum occupancy of both bands is increasing. The transition to DTV requires additional spectrum in the TV bands and rules changes to Part 90 allowing for more efficient use of land mobile radio services is impacting the 450-470 MHz band. Recognizing the value of wireless medial telemetry, the FCC released a Notice of Proposed Rule Making creating a new Wireless Medical Telemetry Service (WMTS).

WMTS would operate on TV channel 37 (608-614 MHz) on a primary basis. The FCC is also proposing to allocate either one band from 1391-1400 MHz or two separate bands, 1396-1400 MHz and 1429-1432 MHz. The FCC seeks comment on whether one contiguous band or two separate bands would be best. Operations in these bands must protect certain government operations. A designated frequency coordinator would have the responsibilty to maintain an accurate engineering database of all WMTS transmitters and to notify users of potential frequency conflicts. WMTS operation would be co-primary with radio astronomy in the 608-614 MHz band, but most not cause interference to radio astronomy operations and must be coordinated with radio astronomy facilities.

More details, including propsed power levels and emssion requirements, can be found in the FCC Notice of Proposed Rule Making, ET Docket 99-255(FCC 99-182). Refer to the FCC News Release (nrwl9030) for a summary of the NPRM.

FCC Proposes Closed Captioning Requirements for DTV Receivers (July 15)
The FCC decided today to propose rules that would require broadcasters and set manufacturers to comply Section 9 of the EIA-708-A standard for the encoding, delivery and display of closed captioning information on DTV systems. Under the FCC proposed rule making, all DTV receivers with picture screens 13 inches or larger would have to include closed caption decoder circuitry that complies with EIA-708A section 9. Set-top DTV converters and DTV tuners would also have to comply with the closed captioning requirements. The rules would become effective one year after adoption by the FCC.

The FCC seeks comment on whether the current screen size labeling standard is appropriate when applied to DTV receivers, which will likely have a an aspect ratio of 19:9 rather than 4:3. For the same diagonal size, a DTV receiver screen will have less area than an analog receiver's screen with the same measurement. The FCC also sought comments on a proposal to require dual analog / digital receivers to have a dual closed caption mode that complies with both the analog and EIA-708-A digital closed captioning standards, depending on the mode in use.

More information may be found in FCC Notice of Proposed Rule Making, ET Docket 99-254, FCC 99-180, available as a text file (fcc99180.txt) or WordPerfect file (fcc99180.wp). An FCC News Release (nret9001) provides a summary of the Notice of Proposed Rule Making.

FCC Proposes Allowing Multichannel Video Programming Distributers Use of 12 GHz CARS Frequencies (July 14)
The FCC has started a rule making to amend its rules to allow private cable operators and other multichannel video programming distributers to use frequencies in the 12 GHz band for delivery of video programming. Under Part 101 of existing FCC rules, these services must use frequencies in the 18 or 23 GHz band. This rule making was initiated by a petition for rulemaking filed by Optel, a private cable operator (PCO) providing video and other services to residential users. The FCC, on its own, extended the Notice to include expanded use of 12 GHz by other Multichnnel Video Progrmmming Distributors (MPVDs). Optel requested use of the band from 12.70 to 13.25 GHz for delivery of video programming.

The 12.70 to 13.25 GHz band includes the 12.70 to 13.20 GHz spectrum assigned to the Cable Television Relay Service (CARS) and the 12.70 to 13.25 GHz band used for Broadcast Auxiliary Stations (BAS). 12.20-13.25 GHz is shared with the Fixed Satellite Service (FSS) for earth-to-space communications.

The FCC seeks comments on the impact of PCO and MPVD use of these frequencies on existing users, including "any existing or future impact this sharing may have with BAS, especially as it relates to the required digital transition for broadcasters." The FCC said it does not propose making any changes to the existing technical and operational characteristics of CARs, but sought comment on "whether PCOs and other MPVDs can operate successfully in the 12 GHz CARS band under the existing technical and operational requirements." Optel and RCN Telecom Services, Inc. (RCN), an operator of open video systems (OVS) argued that access to the 12 GHz band was needed because of the technical limits of the 18 GHz frequencies currently used. While the FCC recognized there were differences in the propagation characteristics between the 12 GHz and 18 GHz bands, it did not believe that the range difference was as great as Optel and RCN suggested. However, the FCC asked, " If Optel's assertion is valid, should PCOs be required to demonstrate that they need to transmit over more than 10 miles before they are eligible for a CARS license?"

The Notice of Proposed Rule Making requests comments on several other issues. If this proceeding is of interest to you, refer to the Notice of Proposed Rule Making - CS Docket 99-250, FCC 99-166.

TECHNOLOGY - Lucent Uses Light Beams for New High-Speed Optical Networking System (July 14(
Lucent Technologies has developed an alternative to RF signals for transmitting information directly through the air. The technology, called WaveStar(TM) OpticAir(TM) uses lasers, amplifiers and receiver placed on rooftops or in windows to transmit and receive voice, data or video traffic. The system uses dense wave division multiplexing to increase bandwidth. Lucent says it will allow data rates up to 10 gigabits per second. Gerry Butters, president of Lucent's Optical Networking Group, said ""Lucent is committed to providing our customers with cutting-edge metro optical networking solutions -- bringing photons not only to the desktop, but to rooftops, windows and ships at sea. By adding this breakthrough technology to our industry-leading portfolio, Lucent soon will be able to provide the power of fiber-optics just about anywhere -- with or without the fiber."

Lucent said the system uses "expanded beam" lasers that meet all applicable environmental safety requirements. Lucent expects to offer a four-wavelength system with a maximum capacity of 10 Gb/s and a range up to five kilometers in the summer of 2000. A 2.5 Gb/s system should be available in March 2000.

More information may be found in the Lucent Press Release and on Lucent's WaveStar OpticAir web page.

SCIENCE - Scientists fear BNL Relativistic Heavy Ion Collider Could Destroy Earth (July 19)
Worried about Y2K? Some scientists fear high powered matter collisions in the new Brookhaven National Laboratories Relativistic Heavy Ion Collider (RHIC) could create sub-atomic particles called 'strangelets'. The concern is that the strangelets, once formed, could start a chain reaction, possibily ending with the creation of a black hole or the disappearance of the planet. A Sunday Times of London article Big Bang machine could destroy Earth quoted John Nelson, professor of nuclear physics at Birmingham University saying the changes of an accident were infinitesimally small but cautioning "The big question is whethr the planet will disappear in the twinkling of an eye. It is astonishingly unlikely that there is any risk - but I could not prove it."

John Marburger, Brookhaven Lab Director, released a statement today in response to the Sunday Times of London article. In the statement, Marburger said "I am familiar with the issue of possible dire consequences of experiments at the Relativistic Heavy Ion Collider, which Brookhaven Lab is now commissioning. These issues have been raised and examined by responsible scientists who have concluded that there is no chance that any phenomenon produced by RHIC will lead to disaster." He pointed out that the amount of matter involved in the RHIC collisions is extremely small and commented "Our universe would have to be extremely unstable in order for such a small amount of energy to cause a large effect. On the contrary, the universe appears to be quite stable against releases of much larger amounts of energy that occur in astrophysical processes."

However, Marburger and Brookhaven National Laboratory are not ignoring the risk Marburger said "I have asked experts in the relevant fields of physics to reduce to a single comprehensive report the arguments that address the safety of each of the speculative 'disaster scenarios.' I expect the report to be completed well before RHIC produces the high-energy collisions necessary for any of these scenarios. When the report is completed, it will be broadly published and placed on the Laboratory's web site."

More information on the RHIC is available on Brookhaven National Laboratory's RHIC Home Page.

DIGITAL TELEVISION STATION APPLICATIONS - See ap990715.txt for more information
Call (DT) Ch. Licensee Location ERP (kW) HAAT (m) Antenna
WATL 25 Qwest B'cstg Atlanta GA 73.8 315 Dielectric TFU-18GBH-R


DIGITAL TELEVISION STATION APPLICATIONS - See ap990714.txt for more information
Call (DT) Ch. Licensee Location ERP (kW) HAAT (m) Antenna
WJLA 39 Allbritton Comm Washington DC 1000 (mod) n.c. no change
WHFT 46 Trinity B'cstg Miami FL 500 308 Andrew ATW19H3-HTPX-45S
WZVN 41 Montclair Comm Naples FL 280 458 Dielectric TUP-SP3-8-1
WFSG 38 Bd of Regents Panama City FL 49.2 137 Dielectric TLP-32A


DIGITAL TELEVISION STATION APPLICATIONS - See ap990713.txt for more information
Call (DT) Ch. Licensee Location ERP (kW) HAAT (m) Antenna
WPXS 21 DP Media Mt. Vernon IL 1000 316 Dielectric TFU-24GTH 04
WTVA 57 WTVA Tupelo MS 257 528 Shively SMP 16L2HSO
WRPX 15 DP Media Rocky Mount NC 180 354 Dielectric TFU-18DSC S190


DIGITAL TELEVISION STATION ACTIONS - See ac990713.txt for more information
Call (DT) Ch. Licensee Location ERP (kW) HAAT (m) Antenna
KSIN 28 Iowa Public B'cstg Sioux City IA 200 611 Non-directional


OTHER Items of Interest

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Last modified July 26, 1999 by Doug Lung dlung@transmitter.com
Copyright 1999 H. Douglas Lung