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.

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January 17, 2000 - Issue 197Final Edition

DTV - Zenith Demonstrates Improvement in 8-VSB Receiver Performance, Impulse Noise Problems with COFDM (Jan. 14)
During the Consumer Electronics Show in Las Vegas, Zenith set up a laboratory demonstration showing the performance of the latest generation 8-VSB decoders. For comparison, Zenith had a Nokia UHF-only DVB-T setup box, recently purchased "off-the-shelf" in England and an older (1-2 year old) NDS UHF-only set-top box. Both used 8 MHz bandwidth, as 6 MHz COFDM/DVB-T units were not available. The COFDM parameters were adjusted to be the same as those used by Sinclair during its tests, with the data rate scaled to maintain the same Mbps/MHz ratio with the 8 MHz bandwidth as Sinclair had when using a 6 MHz DVB-T signal.

The Zenith demonstration showed the second and third generation receivers had approximately a five dB advantage over the Nokia COFDM receiver in white gaussian noise performance. For these tests, white gaussian noise was added to a strong 8-VSB or COFDM signal. The first generation 8-VSB receivers showed only a 2 dB advantage over COFDM.

Perhaps more relevant in the current DTV transmission standard debate, the second and third generation 8-VSB receivers, according to Zenith, "essentially maintained their 5 dB advantage (single quasi-static 1 usec ghost with slowly/0.05 Hz rotating phase) in noisy environments and even gained a couple dB of advantage in a strong ensemble ghost (ensemble D from ATTC)." This indicates 8-VSB should work better than COFDM with weak to moderate signals (less than 30 dB SNR) in a heavy multipath (greater than 50 percent) environment.

Susceptibility to impulse noise is often mentioned as one of the major disadvantages of COFDM for DTV transmission. Messages posted in the uk.tech.digital-tv discussion group illustrate the problems encountered in England with impulse noise from light switches, refrigerators and automobiles. (Search it at www.deja.com, select "Power Search" and enter uk.tech.digital-tv as the forum. I used keywords "digital TV reception noise" as keywords.) Zenith used a hair dryer as a source of impulse noise for its demonstration. The noise was coupled from the AC power line into the RF fed to the tuners through an attenuator to set the level. Noise was increased until it caused errors in the COFDM receiver, then the DTV signal levels were reduced until the 8-VSB receiver took the same amount of burst errors. This two step process is necessary because the characteristics of impulse noise make it difficult to measure the actual noise power. Zenith found that in the presence of impulse noise, the 8-VSB receivers were able to receive signals 23-26 dB below the point of error in the COFDM receivers.

Zenith said the third generation 8-VSB receivers will be field tested publicly in a real world environment to verify the improved laboratory test results. Given the mixed preliminary results of the Motorola tests (see the January 3, 2000 RF Current), it will be interesting to see if the improvements in the laboratory carry over into the field.

SATELLITE - INTELSAT Publishes Results of Latest Interoperability Testing for Digital Video Compression Equipment (Jan. 13)
INTELSAT has released the results of its latest interoperability testing for digital video compression equipment. The testing, conducted from November 29, 1999 through December 3, 1999, demonstated how well different manufacturers video compression equipment works together when set to the parameters commonly used for contribution video applications. Dick Tauber, CNN Vice President, Satellite and Circuits and Chairman of the Inter-Union Satellite Operations Group (ISOG) commented, "This unprecedented cooperation has produced an industry success that will benefit all participants moving into the digital age. ISOG and the WBU (World Broadcasting Union) are extremely grateful to all the manufacturers and to INTELSAT for this cooperation and important achievement."

This goal of this round of testing was to achieve "plug and play" operation for both NTSC and PAL standards, at both 4:2:0 and 4:2:2 profiles at Main Level. The results of the tests are available in Adobe Acrobat format at http://www.intelsat.int/interop/index.htm. This information was obtained from an INTELSAT Press Release.

SATELLITE - Hughes to Sell Satellite Manufacturing Business to Boeing (Jan. 13)
Hughes Electronics Corporation announced it will sell its Satellite Systems Operations to Boeing in an all cash transaction valued at 3,750 million dollars. In a Press Release, Hughes said it was focusing its resources on "its high-growth entertainment, information and business communications services businesses." In addition to the sale of the satellite systems operations, Hughes will also discontinue "certain wireless manufacturing activities and focus on wireless broadband opportunities."

Michael T. Smith, chairman and CEO of Hughes, stated, "These strategic moves accelerate the transformation of Hughes into a highly focused entertainment and data information services and distribution company, We will now be in a stronger position to fuel the growth of our high-growth service businesses, focus more intensely on customer needs, and devote resources to the integration of new broadband and interactive services."

Boeing will be acquiring Hughes Space and Communications Company, which has contracts for five HS 601 HP satellites for PanAmSat and DIRECTV(tm), and five HS 702 satellites for PanAmSat and the new Hughes Spacway(tm) broadband data system. Also included in the transaction is Hughes Electron Dynamics, a supplier of electronic components for satellites; and Spectrolab, a provider of solar cells and panels for satellites.

FCC Issues Order and NPRM on Establishment of a Class A Television Service (Jan. 13)
The FCC released an Order and Notice of Proposed Rule Making in the Matter of Establishment of a Class A Television Service (FCC 00-016). This Order and Notice of Proposed Rule Making (NPRM) replaces the NPRM adopted September 22, 1999. Under the Community Broadcasters Protection Act of 1999 (CBPA), the FCC was required to "prescribe regulations establishing a Class A television license available to licensees of qualifying low-power television (LPTV) stations." Class A licensees would be subject to the same license terms as full-power television licensees and would be given primary status.

The CBPA provided very general protection guidelines for Class TV stations and LPTV stations and full power analog and digital TV stations. It did not specify how interference was to be calculated or even how interference is defined. The FCC Order and NPRM addresses these issues, offering suggestions and requesting comment. The FCC proposes defining Class A TV service area as the 74 dBu contour at UHF, the 68 dBu contour for channels 7-13 and the 62 dBu contour for channels 2-6. The proposed Class A DTV service area definition would match that for full-power DTV stations. The protection ratios for Class A TV stations and other TV stations is a much more complicated issue. The CBPA required Class A TV stations protect full-power DTV stations not only in service area specified in the DTV Table of Allotments, but also the service area resulting from a "maximization" application filed by a full-power DTV station. The CBPA did not, however, how interference was to be calculated nor how issues such as interference between non-collocated adjacent channel stations is handled. The section in the FCC NPRM and Order is too long and too complex to summarize here. Refer to the Order and Notice of Proposed Rule Making in the Matter of Establishment of a Class A Television Service (FCC 00-016). It is available on the web as a text file - fcc00016.txt or as a Microsoft Word file - fcc00016.txt.

The FCC issued an Erratum correcting the filing date for reply comments listed in the Order and NPRM. Comments are due on or before February 10, 2000. Reply comments are due on or before February 22, 2000. The Erratum said. "We have established these relatively short comment periods due to the very short 120 day statutory deadline imposed by the CBPA. Moreover, in order to ensure that we meet the deadline imposed by Congress, we will not extend these comment deadlines."

FCC Antenna Structure Registration Data Now Available Via the Internet (Jan. 12)
In a Public Notice (DA 00-0046) released today, the FCC said the Antenna Structure Registration (ASR) public access files are available for download either from the ULS home page by clicking on the link to Download Complete ULS Databases and Download ULS Daily Transaction Files or by FTP at ftp.fcc.gov/pub/Bureaus/Wireless/Databases/uls. Don't attempt this without reading the details in the Public Notice (DA 00-0046). It describes how file names are created and the data and definition files available.

OTHER Items of Interest

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