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.

This page contains stories from RF Current issues published in August 1997. Links referenced in the articles were current when published but by this time may have changed. If you find a bad link, try connecting to the home page of the publication or company and look for an archive of past articles. If you find a changed link, I'd appreciate it if you'd let me know by dropping me a note indicating the new location at dlung@transmitter.com.

August 25 - Issue 83 Final Edition

FCC Releases OET-65 Bulletin on Evaluating RF Exposure Compliance (Aug. 25)
The FCC Office of Engineering Technology has released its long awaited OET Bulletin 65 on "Evaluating Compliance With FCC Guidelines for Human Exposure to Radiofrequency Electromagnetic Fields". OET-65 is considerably more detailed than OST-65, which it supersedes. OET-65 contains information on evaluating compliance near more complex structures such as parabolic antennas. One handy feature is the addition of tables showing the minimum distance where RF exposure levels are not predicted to be exceeded for various combinations of frequency and power level.

OET-65 was released in two parts. The core document, OET-65, outlines the general procedures for determining compliance, while OET-65A, a supplement, includes tables and formulas specifically for use by broadcasters. OET-65 is available in WordPerfect and Adobe Acrobat formats. It appears some of the figures may be missing in the Adobe Acrobat version. For links to all OET-65 documents, use the FCC web page http://www.fcc.gov/oet/info/documents/bulletins/#65 or visit the ET93-62 Home Page.

FCC Amends Parts 73 and 74 of Rules to Permit Certain Minor Changes without a CP (Aug. 25)
The FCC released its Report and Orderin Mass Media Docket 96-58 "In the Matter of Amendments of Parts 73 and 74 of the Commission's Rules to Permit Certain Minor Changes in Broadcast Facilities Without a Construction Permit". Most of the rule changes dealt with FM broadcast stations, however, some of the changes will be of interest to TV licensees. Some of the changes now permitted without first obtaining a construction permit include (with certain restrictions) replacement of one TV directional antenna with another, changes to the vertically polarized ERP up to the authorized horizontally polarized ERP, and use of formerly licensed main TV facilities as auxiliary facilities.

These new rules are not reflected in current FCC applications. Stations wishing to take advantage of these rule changes should use the forms included in the Report and Order.

DTV - Update - KITV Files for DTV facilites on Haleakala, Hawaii (Aug. 25)
Today's list of FCC Broadcast Applications included an application from Argyle Television, Inc. in Wailuku Hawaii for a new digital TV facility for KMAU-TV on digital channel 29. The ERP was specified as 51.2 KW at an HAAT of 1,770 meters, near the summit of Mt. Haleakala. The antenna specified was an RFS PHP4.

FCC Releases NPRM on Preemption of Local Restrictions on Broadcast Facilities (Aug. 21)
Responding to a "Petition for Further Notice of Proposed Rule Making" filed by the National Association of Broadcasters and the Association for Maximum Service Television, the FCC released a Notice of Proposed Rule Making In the Matter of the Preemption of State and Local Zoning and Land Use Restrictions on the Siting, Placement and Construction of Broadcast Station Transmission Facilities. The petitioners proposed a rule which would set specific time limits for state and local government action in response to requests for approval of broadcast transmission facilities. The time limits requested varied depending on the nature of the request, but in all cases were 45 days or less. If the local government did not act in this time frame the requested would be deemed granted.The petitioners also requested categorical preemption of other local laws restricting transmission facility construction due to environmental or health effects due to RF emissions.

The Commission asked for comments on how far it should go in preempting local regulations. Comments are due October 30, 1997 with reply comments due December 1, 1997. Full text of the Notice of Proposed Rulemaking is available on-line from the FCC in plain text (fcc97296.txt) or Adobe Acrobat (fcc97296.pdf) formats.

TECHNOLOGY - Univ. of Florida Engineers Use Lightning to Test Electrical Systems (Aug. 20)
University of Florida engineers in Gainesville have built their own runway, complete with lighting systems and now plan to launch rockets with wires attached into likely lightning generating clouds. The purpose is to test ways to reduce the expensive damage caused by lightning and also reduce the potential danger to pilots.

Two different runway surfaces will be tested along with two different lighting systems -- one using direct buried cables and stake mounted lights and the other with the light mounted on a metal can with the transformer inside.

More information on this interesting experiment is available in the University of Florida Press Release.

OTHER Items of Interest

August 18 - Issue 82 Final Edition

DTV - KITV-TV Honolulu to Start DTV In 1997 (Aug. 18)
Argyle Television announced today that KITV-TV, its ABC affiliate in Honolulu, will begin broadcasting DTV in December of this year. pending receipt of all necessary permits. Bob Marbut, chairman and CEO of Argyle, said "Channel 4, along with its satellite stations KMAU-TV and KHVO-TV, will be the first to achieve digital transmission in Hawaii and will be among the first to do so in the United States."

Mike Rosenberg, general manager of KITV, added that KITV's DTV transmitters will be capable of delivering four or more digital pictures simultaneous and "...will also offer high-speed Internet and sother data services during most of the broadcast day and a superb, theater-quality picture during prime time." Rosenberg said KITV has invested "$15 million and more than two years of research and planning to enhance the stations."

Argyle's effort in Hawaii should offer a good test of the technical soundness of the 8-VSB U.S. DTV modulation scheme. KITV is located in Honolulu, but KMAU is on Maui and KHVO is located in Hilo on the east side of the big island of Hawaii. All the NTSC facilities are VHF: KITV is channel 4, KMAU channel 12 and KHVO channel 13. The last two have CP's to improve facilities. For DTV, all are on UHF: KITV is on channel 40 at 1,000 kW, KMAU on 29 at 50.1 kW and KHVO on 18 at 50.1 kW.

The topography of the Hawaiian Islands allows reception over great distances. In the early 80's I showed it was possible to receive channel 26 from Wiliwilinui Ridge on Oahu on the Kona side of the Big Island of Hawaii. The propagation path over water was quite variable. KITV has the advantage of an intermediate station in Maui. Haleakala on Maui, at an elevation over 10,000 feet, provides an excellent relay point. It will be interesting, however, to see how the long over water paths affect the 8-VSB digital signals.

FCC Issues Order and NPRM on Use of Frequencies Above 40 GHz. (Aug.15)
Thursday the FCC's Office of Engineering and Technology released FCC 97-267, Memorandum Opinion and Order and Fourth Notice of Proposed Rulemaking in ET Docket 94-124, Amendment of Parts 2, 15, and 97 of the Commission's Rules to Permit Use of Radio Frequencies Above 40 GHz. for New Radio Applications. FCC 97-267 makes available th 59-64 GHz. band for fixed field disturbance sensors and reaffirms an earlier decision limiting spurious emissions from vehicle radar systems operating in the 46.7-46.9 GHz. band. The NPRM portion of FCC 97-267 addresses the proposed spectrum etiquette filed by the Millimeter Wave Communications Working Group.

While manufacturers of systems operating in these bands will be interested in the details of the document, many RF engineers will find the descriptions of new millimeter wave technology interesting. "Synthetic vision" systems for use in airport environments during poor visibility conditions are mentioned as one use of the frequencies above 90 GHz. The full text of FCC 97-267 is available from the FCC web site.

SCIENCE - Notre Dame Researchers Demo Transistorless Approach To Computing (Aug. 15)
University of Notre Dame researchers reported in the August 15 issue of Science on their "first experimental demonstration of a transistorless approach to computing, calling quantum-dot cellular automata (QCA)". In the experiment a single electron was used to control the position of another electron. If a practical implementation of QCA is successful, the researchers said a 4-inch square QCA chip could contain as many as 40 trillion devices.

More details on this revolutionary technology are available in the Notre Dame Press Release and at the QCA Home Page.

INDUSTRY - P-Com, Inc. to Install 40 GHz. Broadcast Video System (Aug. 13)
P-Com, Inc. announced that its Technosystem unit in Italy was award a contract to build a 40 GHz. broadcast video system to serve local TV sets. It will have a "potential transmission capacity of up to 24 channels and will be utilized by RAI in Rome", according to the P-Com Press Release.

The service is part of a "project financed by the European community for the development of a cellular radio system to provide broadband digital TV and multimedia services to subscribers."

More information on P-Com is available at www.p-com.com.

DTV - Lucent Technology to join Microsoft in DTV Team (Aug. 12)
Lucent Technology said Tuesday it would join the Compaq Computer, Intel Corporation and Microsoft Corporation "DTV Team" in their effort to bring new, affordably priced digital broadcast services to market. In its Press Release, Lucent said its Microelectronics Group is "developing a DTV receiver reference design architecture that will be compatible with the DTV Team's HDO proposal for adding new capabilities as the technology develops." Lucent is also involved in the design and implementation of encoder / decoder circuits for ":higher resolution signals." Last year Lucent said it was working with Mitsubishi to jointly develop HDTV chip sets.

Lucent received commendations from other members the DTV Team, including Craig Mundie, senior VP of Microsoft's consumer platform division, who said: "Their core competencies in the area of microelectronics will be of great value to our partners as they move forward in implementing convergence products in 1998 and 1999. Of paramount importance to the broadcasters is Lucent's CODEC and telecommunication product families.

OTHER Items of Interest

August 11 - Issue 81 Final Edition

SATELLITE - PanAmSat Announces Successful Launch of PAS-6 (Aug. 8)
PanAmSat announced that "PAS-6, the first of three high-powered broadcast satellites built by Space Systems/Loral (SS/L) for PanAmSat Corporation of Greenwich, Conn., was successfully launched in orbit at 2:46 a.m. Eastern Time from Kourou, French Guiana." The satellite's on-board power is is over 10 kilowatts, with a total satellite transmitter RF power greater than 3600 watts, divided among 36 Ku-band transponders. PanAmSat claims this makes it "one of the most powerful communications satellites ever launched." The satellite will be stationed at 43 degrees West longitude.

More technical details are available in the Loral News Release. Earlier this week Loral announced it received an order to build a third digital audio radio service (DARS) satellite for CD Radio. Information on this satellite is also available in a Press Release.

DTV - Comark Announces Agreement with MRC for DTV STL Microwave Products (Aug. 7)
Comark Digital Services said it had reached an agreement with MRC, a division of California Microwave, "to offer integrated systems for digital television.". Broadcasters will, in most cases, have to transmit their digitized conventional NTSC TV signal along with the compressed DTV signal using the same spectrum they are now using for one analog TV STL (Studio Transmitter Link). California Microwave has posted an application note on Converting from Analog to Digital Video STLs, along with other digital microwave information on their web site at http://www.cm-mrc.com.

TECHNOLOGY - Robot "LawnNibbler" Cuts Grass, Not Kids (Aug. 6)
Kevin Hakala, a graduate student at the University of Florida's Machine Intelligence Laboratory has developed a robot lawnmower that uses a combination of an RF activated perimeter wire, sonar and infrared sensors and emitters to know where its been what what obstacles are in its way. Hakala said ":It will trim the grass in a defined area while avoiding obstacles such as trees, children, toys or pets. It uses two smart systems: one to tell it where it is and another to tell it what to avoid."

More information is available in a News Release from the University of Florida.

OTHER Items of Interest


August 04 - Issue 80 Final Edition

TECHNOLOGY - Acrodyne Introduces Single Tube Dual Channel Transmitter Line (July 31)
Acrodyne announced it has developed a method of combining an NTSC analog UHF TV signal with an adjacent channel DTV signal, all in the same transmitter. Acrodyne calls it "ACT (for Adjacent Channel Technology)". Acrodyne's press release used a transmitter equipped with a Diacrode with a peak envelope power rating of 104kW as one example. It could transmit a 25kW NTSC visual signal, a 2.5kW NTSC aural signal and a 2.5 kW DTV signal simultaneously. Additional amplifiers can be added for more power capability and the ratios between the various signals adjusted, so long as the peak power does not exceed the tube's rating.

One advantage of this technology is that a station could change the ratios to favor the DTV signal when digital sets become more widespread. The transmission of three signals through one amplifier will require excellent linearity to prevent intermodulation products from creating interference among the signals.

More information on this technology is available in the Acrodyne Press Release and on Acrodyne's Engineering Forum, accessible through a marketing survey form. You can bypass the form by clicking on the link at the top of the form to indicate you've already filled it out.

SATELLITE - Motorola Announces First Iridium Space to Ground Mobile Tests (July 31)
In a Press Release issued today, Motorola said it had established IRIDIUM(R) system satellite-to-ground mobile paging and radio communications links. Motorola claims these are the first such transmissions through a low-earth orbit mobile satellite communications system. The Motorola release said "On July 3, an IRIDIUM satellite transmitted hundreds of messages to IRIDIUM prototype pagers during a South-to-North orbital pass over Motorola's Satellite Communications Group (SCG) Chandler facility. The first links between the satellite and IRIDIUM prototype phone handsets were made July 7."

According to the release, the phone handsets weren't talking to each other. Instead, they transmitted ring channel burst signals. These signals enable the handset to locate and acquire the satellite. They will be able to handle voice, fax and data messages. The system is expected to be activated commercially late in 1998. Amateur Radio licensees have experimented with communications through low earth orbiting satellites for over a decade. More information on this side of the LEO story is available from AMSAT.

DTV - CEMA President Predicts Rapid DTV Acceptance (July 29)
Gary Shapiro, President of the Consumer Electronics Manufacturers Association (CEMA) told attendees of the Marketing Society of the Cable and Telecommunications Industry National Marketing Conference that "American consumers always wanted the best entertainment products the market could provide."

He predicted that HDTV will become the preferred medium for TV advertisers, with Superbowl ads in HDTV by 1999. He also saw most prime time network programming shot in HDTV by 2000 and one million HDTV sets sold by 2000. He suggested HDTV sets will be in short supply, saying 30 million Americans are early adopters of new technology and noting 18 million Americans have spent over $2,000 on large screen TV sets, which will be ready for replacement in the next few years. Additional predictions are contained in the CEMA News Release.

OTHER Items of Interest



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Last modified August 25, 1997 by Doug Lung dlung@transmitter.com
Copyright 1997 H. Douglas Lung