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 September 20 - Issue 183

September 27, 1999 - Issue 184 Final Edition

DTV - Sinclair Will Host Satellite Video Conference on the DTV Reception Issue (Sept. 27)
Sinclair announced it will hold a satellite video conference on October 7, 1999 "to inform interested parties of the results of the Baltimore tests and SBG intention to file FCC petition the following day." The video conference will open with remarks by Sinclair CEO David Smith. Nat Ostroff will report on the Baltimore tests. Martin Leader will present the Proposed FCC petition. This will be followed by discussion via email and 800 number.

The Conference will be held on Telstar 4, transponder 17 (4040 MHz), 6.8 and 6.2 MHz audio.

DTV - Sinclair Releases Results of Baltimore 8-VSB vs. COFDM tests (Sept. 27)
Nat Ostoff, Sinclair's Vice President, New Technology, presented the results of his comparative reception tests of 8-VSB and COFDM in a session at the IEEE Broadcast Technology Society Symposium in Wasington, D.C. Friday morning. Speaking to a standing-room only crowd, Ostroff carefully described the tests that showed that the 8-VSB receivers were incapable of adequate performance with indoor receive antenna when compared with COFDM DVB-T receivers. One of the COFDM receivers, from NDS, was manufactured in March, 1997. The COFDM units were modified for the U.S. 6 MHz TV channel bandwidth. The COFDM data rate transmitted was 18.67 Mbps, slightly less than the 19.39 Mbps ATSC data rate with 8-VSB but sufficient for HDTV transmission.

Using a simple UHF fan dipole indoors, testing showed that at the 31 sites tests, 8-VSB was receivable at 11 of the sites. The COFDM transmission, at the same average power level, was receivable at all 31 sites. A two-bay dipole indoor antenna didn't help 8-VSB reception. Using this antenna, only 7 of the 31 sites could receive the 8-VSB transmission. As before, all 31 sites were able to receive the COFDM transmission.

Ease of reception was tested by measuring the number of degrees the receive antenna could be rotated before loss of reception. Again, COFDM significantly outperformed 8-VSB. The tests found that "in no location, under any conditions, was it possible to receive 8VSB with spectrum deviations in excess of 15 dB." COFDM, however, could be received with major spectrum deviations as large as 25 dB. COFDM also performed better under dynamic multipath conditions.

Analysis shows that 8-VSB should have a theoretical advantage over COFDM in carrier-to-noise (C/N) ratio as large as 4 dB. The Sinclair tests showed that while they were able to measure an 8-VSB advantage of approximately 2.0 dB in the field, no situation was found where 8-VSB could be received and the COFDM transmission could not, including fringe areas. Sinclair's report said, "It may be surmised from these results that the 2db real world C/N advantage for 8VSB, in this generation of receivers, is swamped by other path impairments that render the two system equivalent at the fringes." Sinclair used Panasonic and Pioneer tuners for the tests.

Other papers presented at the IEEE Broadcast Symposium showed existing 8-VSB receivers exhibited a wide range of performance. Two of the latest receiver designs were better than the Grand Alliance reference decoder. Two of the current receivers were significantly worse. Were these the two used in the Sinclair tests? The two papers on 8-VSB receiver performance did not link specific manufacturers to the results.

The complete text of the Sinclair testing is available on-line in Adobe Acrobat format, in both complete (438k) and short (84k) formats. An Acrobat version of the complete presentation is also available in a 1M file. All versions may be downloaded from the Sinclair DTV Page. The long version includes complete details on the test procedures, equipment lists and photographs.

FCC Notice of Proposed Rule Making to Modify DTV Table of Allotments in Reno, NV (Sept. 24)
Sarkes Tarzian, Inc., licensee of KTVN, NTSC Channel 2 in Reno, NV has requested the substitution of DTV Channel 13 for its assigned DTV Channel 32. Sarkes Tarzian stated the substitution would facilitate its relocation of its DTV transmitting facility and the implementation of a common DTV antenna facility it is now comtemplating. The FCC found the channel change would meet its allocation requirements. The technical parameters of the modified allotment on Channel 13 would specify an effective radiated power of 12 kW at a height above average terrain of 906 meters.

Interested parties may file comments on or before November 15, 1999. Reply comments are due on or before November 30, 1999. Refer to the Notice of Proposed Rule Making (MM Docket 99-291) for details on the request and information on filing comments.

DTV Summitt to Focus On Programing, Status of Transition (Sept. 23)
The Consumer Electronics Manufacturers Association (CEMA) will host its fifth Digital Television (DTV) Summit in Los Angeles, California on September 28, 1999. There will be an opening reception on September 27th featuring Monday Night Football live on HDTV. The Summit is open manufacturers, broadcasters, cable and satellite executives, retailers, content providers and media. More information is available at www.CEMAcity.org/dtvsummit/ and in the CEMA Press Release.

SATELLITE - Onsat Asks FCC for C-band VSAT licenses, FCC Grants STA for EchoStar 5 tests (Sept. 23)
The FCC found Onsat's Petition for Declaratory Ruling and Waiver acceptable for filing. Onsat is seeking a Declaratory Ruling to permit blanket licensing for C-band satellite earth stations using VSAT technology, subject to frequency coordination. Onsat also asked for a waiver, if necessary, of Section 25.212 of the FCC rules to permit Onsat to obtain routine authorizations for 3.7 meter dishes operating in the C-band. This is from FCC Report No. SAT-00026, Public Notice pnin9183. This document is in Adobe Acrobat format.

The FCC, by Order (da991852, File No. SAT-STA-19990824-00085), granted EchoStar Satellite Corporation's request for an STA (Special Temporary Authority) to test Direct Broadcast Satellite, EchoStar 5 on its channels at 110 degree West Longitude, in addition to channels 28, 30 and 32 at this location. While this operation had the potential to interfere with DIRECTV's DBS-1 satellite when it is located at 110 degrees. EchoStar said DBS-1 was not expected to be operational for at least 6 weeks. The FCC granted the EchoStar STA "on the condition that it does not conflict with usage by authorized users of the spectrum and does not cause harmful interference to any authorized user, such as DIRECTV."

SCIENCE - Ornithologists Say Communications Towers Kill Birds (Sept. 22)
On January 22, 1998 - a foggy, snowy night in western Kansas - an estimated 10,000 migrating Lapland longspur birds were killed when they collided with a 420 foot television tower, according to Albert M. Manville, a biologist from the U.S. Fish and Wildlife Service Office of Migratory Bird Management. More birds, shown in a photo in a release from Cornell University release titled Birds vs. Towers: Ornithologists fear growth of communications industry, where found at the base of a 850-foot television tower near Elmira, NY in the wake of Hurricane Floyd.

Bill Evans, a consulting ornithologist for the Cornell Laboratory of Ornithology stated, "The more towers, the more dead birds" in a session titled Avian Mortality at Communications Towers at the annual American Ornithologists' Union meeting at Cornell University. According to the Cornell Release noted above, Albert Manville warned television stations converting to the digital format in the United States plan to erect more than 1,000 'megatowers', each at least 1,000 feet tall. Although the meeting included representatives from the Federal Communications Commission, the National Association of Broadcasters and the wireless communications industry, the Cornell release did not report any disagreement with that number.

Robert C. Beason of the State University of New York at Geneseo explained that the red lights or radio signals from communications towers may interfere with avian navigation systems, causing birds to circle to restablish orientation cues. In this state, the birds are more likely to collide with the tower or guy wires. Many other birds, escaping collision but exhausted from circling, fall to the ground. The precise immpact of communications towers on birds is unknown, because predators often consume the birds before biologists arrive. Some estimates say as many as 100 million birds may be killed each year in collisions of all kinds. Bill Evan set up equipment at the base of a 317 foot communications tower in north-central Nebraska using upward-pointing microphones to listen to migrating ducks. He said, "I could hear their alarm calls, the collisions, the sounds of ducks falling to the ground."

The meeting did offer some means to reduce the bird death toll. Michael Mesure of the Fatal Light Awareness Program in Erin, Ontario said that voluntary cutbacks on lighting in tall buildings are "saving thousands of avian lives in downtown Toronto.". He also reported that bird collisions decreased dramatically "when Ontario Hydro replaced spot litghts with rapidly flashing strobe lights on emission stacks at six electrical generation stations."

More information may be found in the report Birds vs. Towers: Ornithologists fear growth of communications industry from Cornell University. Also refer to the Cornell Laboratory of Ornithology web site and www.towerkill.com.

OTHER Items of Interest

>>> Next >>> October 4 - Issue 185


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Last modified September 28, 1999 by Doug Lung dlung@transmitter.com
Copyright 1999 H. Douglas Lung