The National Association of Broadcasters (NAB) and the Association for Maximum Service Television, Inc. (MSTV) emphasized the importance of guidelines for DTV receiver performance and interference immunity in the digital transition. In comments
filed in response to the FCC Notice of Inquiry, Interference Immunity Performance Specifications for Radio Receivers. NAB and MSTV explained, "In a closed system, such as most commercial wireless networks, the network operator controls both the transmitters and receivers, and is thereby able to optimize its network to minimize interference with little need for government involvement. However, in an open system such as broadcasting, in which broadcasters have no control over the devices that are used to receive the transmitted signals, there is a need for greater coordination and some form of standardization to ensure that television sets purchased by consumers are able to adequately receive over-the-air broadcast signals."
The comments said that while receivers are getting better, many DTV receivers currently on the market need further improvement. The filing referenced my July 9, 2003 TV Technology article on DTV Reception (available at www.tvtechnology.com
) describing ATTC tests showing some current receivers do not provide the performance assumed by the planning factors used to generate the DTV Table of Allotments. The filing did not ask for mandatory receiver performance standards, but said the FCC should monitor and, "if necessary, promote the process to improve over-the-air DTV receiver technology." It supported current efforts ATSC, along with the Consumer Electronics Association (CEA) and individual manufacturers, is taking to develop a formal Recommended Practice for broadcast DTV receiver performance.
NAB and MSTV listed six issues that should be addressed in a performance standard:
- "Antenna control interface"
- "RF signal operating range, including both UHF and VHF sensitivity"
- "Noise performance"
- "Phase noise performance"
- "DTV to DTV and NTSC to DTV interference immunity (co-channel, adjacent channel and taboo channel)"
- "Equalizer performance, including equalizer range, as well as multi-path performance"
Future re-packing of the television band will require that receiving devices, at a minimum, meet the performance criteria assumed under the planning factors used to allocate DTV channels.
While not asking for the FCC to set DTV receiver standards, it asked the FCC to oversee the relationship between broadcasters and consumer electronic manufacturers, stating, "The necessity for such oversight is due to the fact that the digital transition is at a critical stage. Inadequate reception by new DTV receivers may delay or derail the off-air digital transition. Also, some in the consumer electronics industry are sending mixed signals." NAB and MSTV said, "In a perfect world, interested parties would work together to ensure that DTV receivers operate as anticipated, obviating the need for a government role. However, it remains unclear whether manufacturers perceive the over-the-air DTV market as being important." As an example, the filing pointed to the CEA challenge to the FCC Order requiring DTV tuners in all TV sets larger than 13 inches by July 2007 and said, "representatives of the consumer electronics industry appear to have shifted their focus to the manufacture of digital receiving devices for cable as opposed to over-the-air television."
MSTV and NAB also opposed the FCC plan to allow unlicensed devices in the TV broadcast band, describing the congestion in the TV band now and the various services using it. "Already, trade-offs with respect to the public's free, over-the-air television service have been required to undertake a transition within the existing broadcast spectrum -- new interference to existing analog broadcast service, limitations with respect to digital service areas, and displacement of secondary services such as low power stations and translators have been necessary to accomplish this historic feat. After the transition, maximized DTV facilities, Class A stations, low power stations, translators and boosters need to be accommodated within the core broadcast spectrum. Moreover, both during and after the transition, other devices such as wireless microphones, wireless assist video devices, remote control devices, and medical telemetry equipment add to the crowding of the broadcast spectrum." Given this congested environment, NAB and MSTV said "DTV receiver performance standards are needed to improve and eliminate problems associated with existing DTV reception, and should not be used as a justification to introduce an 'overlay' of unlicensed operations in broadcast spectrum."
I covered some of the key points in the joint MSTV and NAB comments. For more detail and for NAB's comments on interference immunity performance of AM and FM radio receivers, please read the NAB and MSTV Comments on Interference Immunity Performance for Radio Receivers and Review of the Commission's Rules and Policies Affecting the Conversion to Digital Television
As expected, the American Radio Relay League (ARRL) comments focused on the impact of receiver performance on amateur radio operations. The ARRL comments
said, "The Commission should implement either mandatory receiver immunity standards, or at least guidelines, in most services. From service to service, and even intraservice, different receivers used for different functions in different environments will require unique standards. These standards should be established cooperatively among the Commission and industry, licensees and standards setting organizations and consumer groups. The most pressing need, however, is for improved immunity of consumer electronic devices and systems. The Commission has had the authority to require this for many years, and has failed repeatedly to exercise it. The explosive growth of unlicensed devices which are RF-susceptible has stymied allocations otherwise proper and reasonable in certain frequency bands, and it has resulted in many thousands of instances of complaints against Amateur Radio operators and in some cases, civil and criminal actions being filed. At the same time, no receiver immunity standards are necessary or practical in an essentially experimental radio service such as the Amateur Service." The comments said the FCC has "had the authority to implement interference immunity standards for home electronic devices for more than twenty years."
"ARRL continues to believe that receiver immunity should be on the order of 3 V/m for receivers that might be in the near field of an Amateur Radio station. At that distance, a receiver would be immune to an approximately 100-W ham radio transmission into a 0 dBd antenna 100 feet away. The League conceded, however, that such a standard would not address the interference immunity of telephones, computers, alarm systems, audio systems and other consumer electronics that "constitute the bulk of the instances of interference involving Amateur Radio operators."
A summary of the ARRL comments is available in the Press Release, ARRL Urges Improved RFI Immunity Standards for Consumer Electronics