08.04.2003 12:00 AM
House Bill Mandates Dual Digital Cable-Ready/Broadcast TV Sets, Minimum Power for DTV Stations
A bill introduced in the House of Representatives seeks to expedite the transition to digital broadcasting by requiring the FCC mandate that consumer electronics manufacturers include both digital cable and over the air tuners in future sets, as well as set standards for minimum digital broadcast signals.

The "Consumer Access to Digital Television Enhancement Act of 2003", sponsored by Reps. Rick Boucher (D-VA) and Lee Terry (R-NE) states "within 30 days after the date of enactment of this Act, the Federal Communications Commission shall, by regulation, adopt and implement the regulations proposed in the memorandum of understanding between the cable and consumer electronics industries filed with the Commission on December 19, 2002, as contained in the Commission's notice of proposed rulemaking concerning compatibility between cable systems and consumer electronics equipment ( FCC 03-3; adopted January 7, 2003)."

In support of over-the-air DTV reception, Section 3 of the Bill expands the regulations proposed in the "plug and play" memorandum of understanding: "Regulations adopted by the Commission under subsection (a) also shall require that all television receivers marketed or labeled as `digital cable-ready' include the capability to receive off-the-air digital television broadcast signals transmitted in conformance with part 73 of the Commission's rules."

Some broadcasters operating with very low power DTV transmitters may be required to increase power under the House Bill. Section 4 of the Bill states, "Within 90 days after the date of enactment of this Act, the Federal Communications Commission shall revise its regulations to establish minimum power levels and deadlines for achieving such power levels for any television broadcasting facility transmitting a digital broadcast signal. Such regulations, at a minimum, shall require broadcasters to transmit a digital signal at sufficient power to ensure that its digital broadcast service matches the Grade A service contour of its NTSC broadcast signal by no later than July 1, 2004. Nothing in this Act shall limit the Commission's authority to prescribe higher power levels consistent with the objective of concluding the transition to digital television by December 31, 2006."

The quote in the paragraph above is the full text of the section of the Bill requiring minimum DTV power levels. As I read it, the Bill would require stations to duplicate their Grade A contour with their DTV contour. While it is possible this could be a problem for some stations using directional antennas, some quick calculations show the DTV effective radiated power levels required to duplicate the Grade A contours of an analog station are not that high. Using the FCC contour calculator on the Hammett and Edison Web site, I calculated the distance to the Grade A contour from a maximum power analog facility operating with a height above average terrain of 1,000 feet. The calculated distances to the Grade A F (50,50) contour are 34 miles for a 100 kW low-band VHF TV facility, 40 miles for a 316 kW high-band VHF-TV facility and 40.3 miles for a 5,000 kW UHF TV facility. The Grade A contour field strength is defined as 68 dBuV/m for low-band VHF, 71 dBuV/m for high-band VHF and 74 dBuV/m for UHF TV. As the same height above average terrain, the amount of DTV effective radiated power a UHF DTV station requires to put a 41 dBuV/m F (50,90) contour at the same distances works out to 1.2 kW ERP for 34 miles (matching the low-band VHF Grade A contour), 7.6 kW for 40 miles (to match the high-band VHF Grade A contour) and 8.2 kW for 40.3 miles (to match the UHF Grade A contour). If the FCC decides to use the "city grade" DTV power level, which is 48 dBuV/m at UHF, the required effective radiated power would increase five times.

The full text of the "Consumer Access to Digital Television Enhancement Act of 2003" is available at the Library of Congress Web site thomas.gov. Enter HR2825 in the "Bill Number" box in the upper left of the page under "Search Bill Text 108th Congress (2003-2004)."



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