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 April 24 - Issue 211

May 1, 2000 - Issue 212 Final Edition

DTV - Geocast Announces Successful Field Trial (May 1)
Geocast Network System said that on April 6, 2000 it began broadcasting "personalized rich media" content over ABC affiliate KNTV-DT in San Jose, CA. The broadcasts were received by testers including Geocast employees and their friends and families. The data broadcasts included video clips, utility software, MP3 audio, games and more. Geocast said these in-home field tests were the first "outside the lab" end-to-end evaluation of the Geocast service.

More information is available in the Geocast Press Release.

FCC Satellite Applications (Apr. 27)
Some of the more interesting satellite applications in the FCC Satellite Policy Branch Information Report SAT-00042 (Adobe Acrobat PDF file) include an application by Columbia Satellite Corporation to launch and operate a C-band satellite, Columbia 515R, at 37.5 degrees West Longitude serving the Atlantic Ocean Region and another C-band satellite, Columbia T5R, at 174.3 degrees West Longitude. The latter satellite would be a replacement for its licensed capacity on the TDRS-5 satellite and would serve the Pacific Ocean Region. PanAmSat requested Special Temporary Authority to modify the parameters of its PAS-5 satellite to enable it to provide coverage of the Sydney 2000 Olympic Games. Authority was requested to use 12.25-12.7 GHz on a secondary, non-interference basis, to downlink transmissions at an earth station in Napa, California, from August 1 to October 15, 2000.

SCIENCE - Atomic-sized Nanotubes Show Promising Tunable Structure (Apr. 25)
University of North Carolina at Chapel Hill (UNC-CH) researchers are investigating the electronic properties of carbon nanotubes about a billionth of a meter in diameter. The tiny, thread-like clyinders can behave either as metals or as semiconductors, depending on their chirality - the folding direction of the graphene sheet forming them. However, before the tubes can be used in electronic equipment, it is necessary to know how to fabricate materials with controlled structure and properties.

UNC-CH researchers are making progress in this area. UNC-CH physicist Yue Wu explained, "We used carbon-13 nuclear magnetic resonance (NMR) to measure the number of current-carrying electrons in single-walled nanotubes and therefore their electronic properties. In a sense you might say we wanted to take the 'pulse' of nanotubes by finding out how the carbon atoms in them feel and behave and thus distinguish the metallic nanotubes from the semiconducting nanotubes."

Potential uses of the nanotubes may include flat panel display and telecommunications devices, fuel cells, Li-Ion batteries, high-strength composites and "novel molecular electronics." Refer to the UNC Research News Release for more information.

DTV - Modulation Sciences Choses NxtWave Chip for Pro DTV Reference Receiver (Apr. 24)
Modulation Sciences is using the NxtWave NXT2000 8-VSB demodulator for their msi2080 professional-grade high definition reference receiver. According to the NxtWave Press Release, the NXT2000 "greatly exceeds the performance demonstrated by the Grand Alliance reference system at the Advanced Television Test Center (ATTC)." Some of the features of the NXT2000 include a built-in signal quality indicator to ease antenna alignment, signal acquisition in 50 milliseconds or less (allowing channel surfing), and an equalizer range from -4.5 microseconds to 44.5 microseconds. NxtWave says the on-chip carrier recovery circuitry, along with the equaliztion scheme used in the chip allow robust and dependable demodulation even when the VSB pilot is destroyed.

The NxtWave Press Release said, "the NXT2000 cancels transmission channel impairments such as static and dynamic multipath, phase noise, adjacent or co-channel NTSC interference and impulse noise." Eric Small, CEO of Modulation Sciences, Inc., explained why he chose the NXT2000: "We selected the NxtWave 8-VSB demodulator for its superior dynamic and static multipath performance which is equivalent to other third-generation devices. This demodulator depicts our attention to providing significantly better on-air signal integrity."

OTHER Items of Interest

>>>>Next May 8 - Issue 213

RF Current Index

Return to The RF Page @ www.transmitter.com

Last modified May 23, 2000 by Doug Lung dlung@xmtr.com
Copyright ©2000 H. Douglas Lung