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(week) or two to complete each issue. Articles may be posted earlier if time permits or if there is a major, breaking story.

<<< Back to December 11 - Issue 243

December 18, 2000 - Issue 244 Final Edition

FCC Issues NPRM to Streamline Earth Station Application Processing (Dec. 14)
The FCC has issued a Notice of Proposed Rule Making - FCC 00-435 proposing revision of Part 25 of its earth station licensing rules to streamline the filing requirements for routine and non-routine earth station applications. Also proposed are changes relaxing the power and power density requirements for earth stations, allowing some temporary fixed earth stations to begin operation on an accelerated basis, streamlining VSAT rules and adoptiong a simplied license application form for "routine" earth statiosn.

The FCC NPRM states, "none of the proposals herein affect the pre-licensing coordination requirements between earth station applicants and terrestrial operator that exist today." The coordination requirements under Section 25.203(b) would remain in effect. The FCC does not anticipate any of the proposals in the NPRM would affect the contours of any FSS earth stations operating in shared bands.

The NPRM would modify the requirement that applicants seeking to use an earth station antenna that is non-conforming with Section 25.209(a) must rely upon "a finding by the Commission that unacceptable levels of interference will not be caused under conditions of uniform 2 degree orbital spacing." At this time the FCC requires antenna gain patterns and a technical study, usually in the form of an analysis using the Adjacent Satellite Interference Analysis (ASIA) program. In the NPRM, the FCC recognizes that the data needed for the ASIA are not readily available from any one source and the results of an ASIA can be subject to interpretation. In addition, ASIA results for operation with a non-routine antenna must be coordinated with adjacent satellite operators. As such, the FCC said, "The ASIA requirement often delays the introduction of new services and technological innovation to the public."

The FCC proposes to give applicants seeking authority to use non-routines two other options. One is requiring the earth station operator to reduce its power enough to avoid potential adjacent satellite interference. The second is requiring the earth station operator to submit affidavits from space station operators showing that they have coordinated the earth station's non-routine operations with all other affected satellite system. Other options will be considered, although the FCC said, "Deciding not to pursue either option, however, may require other conditions to be placed on the license." Refer to the NPRM for the details.

To eliminate delays caused by requests for antenna gain patterns, the FCC proposes requiring earth station applications submit a copy of these patterns when seeking authority to use non-conforming antennas.

Recognizing that the FCC has significantly decreased earth station antenna diameter requirements as these smaller antennas were able to meet the side lobe requirements of Section 25.209. However, while antenna diameters decreased, so did mainbeam antenna gain, requiring more input power to the antenan to achieve the same EIRP towards the satellite. The NPRM invited "interested parties to propose higher power limits in Part 25 to reflect technological advances and smaller antenna requirements." Commenters should demonstrate their proposed power levels would protect existing and future users from receiving and causing harmful interference to or from adjacent satellite networks and should also show the levels would be consistent with the FCC's RF exposure limits.

The FCC has received petitions from Spacenet and Hughes Network System proposing methods for determining and setting limits on the total average power radiated towards a target satellite VSAT systems using multiple access techniques including TDMA, FDMA and CDMA and random access schemes such as Spacenet's Aloha technique. The NPRM prposes revising Sections 25.134(a) and 25.212(d) to include the following language: "The maximum transmitter power spectral density of a digital modulated carrier into any GSO FSS earth station antenna shall not exceed -14.0 - 10log(N) dB(W/4 kHz)." Section 25.134(a) would specify different values of "N" for systems using FDMA, TDMA, CDMA or Aloha multiple access techniques. The derivation of the equation is described in Appendix E of the NPRM.

While Part 25 addresses compliance with RF emission rules when apply for an earth station license and when seeking authority to amend a pending license application, the RF requirements for license modification applications to add transmitters are left implicit. Under the NPRM, Section 25.117 would be amended to cross-reference the RF rules explicitly, including, but not limited to, modifications to add transmitters at a particular site.

Under Section 25.274, in cases where an earth station receives interference and determines that the source is not a terrestrial operatior or another earth sation communicating with the the same satellite, Section 25.274(c) directs the earth station operator to contact the control center of the satellite system. Section 25.274(g) states "a representative of the earth station suffering undue interference" has the responsibility to contact the control center for the satellite system suspected of causing the interference. This can be misinterpreted as requiring the earth station operator to contact the satellite operator suspected of causing interference.

Recognizing that satellite operators have little incentive to cooperate with earth station operators using a competing satellite system, satellite operators have more of an incentive to maintain a good working relationship with each other. Therefore, the FCC is proposing to modify Section 25.274(g) "to clarify that earth station operators are permitted to contact the control centers for the satellite systems with which they communicate in cases of harmful interference, and to rely on the satellite system operators to contact the control centers of the potentially interfering satellite systems and resolve the interference."

The Notice of Proposed Rulemaking contains many other rule changes and more detailed technical information on the proposed changes. The Notice of Proposed Rulemaking, 2000 Biennial Regulatory Review -- Streamlining and Other Revisions of Part 25 of the Commission's Rules Governing the Licensing of, and Spectrum Usage by, Satellite Network Earth Stations and Space Stations, IB Docket 00-248 is available for downloading as a text file, fcc00435.txt or Word document fcc00435.doc.

DTV - CRC Releases Report on Phase 1 of DTV Tests (Dec. 11)
The Communications Research Centre Canada (CRC) has released a draft report on Phase 1 of its laboratory and field tests to evaluate the performance of ATSC 8-VSB receivers.

The laboratory tests showed the earliest receivers tested (June 1999) "were very sensitive the phase of the echoes." Later receivers (August 2000) "were significantly less sensitive to the phase of the ghosts and had a wider (-2 to 40 Áseconds) equalizer window." The tests found, however, that robustness to pre-ghosts still needs improvement.

In the field tests, 8-VSB could be received at all but 4 of the 43 sites when an outdoor antenna mounted 10 meters above ground was used. However, 8-VSB indoor reception was possible using simple set-top antennas at only about half of the sites. The report concludes, "Based on the available data, reliable indoor DTV reception also appears to be strongly dependent upon the antenna orientation and location, regardless of its directivity."

The draft report includes several observations based on the indoor measurements. The researchers found two things happened when the indoor antenna was moved away from a "suitably oriented window" - field strength decreases and the level of multipath increases. When the antenna was moved away from its original location, peaked for maximum power and spectral flatness, to the Point of Usability (POU) other reflections tended to be picked up from adjacent houses or buildings. The reflections got in through doors and/or windows and combined with the main signal. The draft report noted that, since the main signal is somewhat weaker at the POU, these reflections become more significant.

Full details on the equipment used, diagrams and photos of the test configurations and spectrum analyzer plots and tables outlining the results are in the 53 page report, available in Adobe Acrobat format from www.crc.ca/research/broadcast/cdtv_report_8.2.pdf.

FCC Notice of Proposed Rule Making to Modify DTV Table of Allotments in Great Falls, MT (Dec. 15)
KRTV Communications (KRTV), licensee of station KRTV, NTSC Channel 3 in Great Falls, Montana has requested the substitution of DTV Channel 7 for its assigned DTV Channel 44. MPBC claims that, "it can reduce the costs of building-out and operating its DTV station by transmitting on a VHF DTV channel." It also noted the operate on the VHF channel would improve signal coverage for viewers in the Great Falls DMA.

The FCC has found this channel change would meet its requirements and warrants consideration. However, because KRTV is located within 400 km of the U.S.-Canadian border, Canadian government concurrence must be obtained. The technical parameters of the modified allotment on Channel 7 would specify an effective radiated power of 160 kW at a height above average terrain of 180 meters.

Interested parties may file comments on or before February 5, 2001. Reply comments are due on or before February 20, 2001. Refer to the Notice of Proposed Rule Making (MM Docket 00-246) for details on the request and information on filing comments.

OTHER Items of Interest

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