FCC Considers Channel 51 Interference Issues in 700 MHz NPRM

The FCC has released its latest NPRM on setting service rules for the 700 MHz band.

The FCC said much of the NPRM is devoted to consideration of the size of service areas and the amount of spectrum devoted to these service areas. The NPRM also addresses power limits in the 700 MHz band. Changes in either could affect the amount of interference broadcasters on channel 51 receive from new services operating on what is now channel 52.

The FCC NPRM (in dockets WT 06-150, CC 94-102 and WT 01-309), seeks comment on whether, and to what extent, there would be an impact on the need to provide protection to TV Channel 51 if the commission provided for licensing areas that are smaller than the economic area groupings in the adjacent lower 700 MHz band "Block A."

"Comments should address how any need for small and rural carriers to provide adjacent TV Channel 51 protection might affect their ability to provide service to those areas if Block A were designated for small area licensing," the commission said in its notice.

The effective radiated power limit for the lower 700 MHz band is 50 kW, although to protect adjacent channels, base stations operating at power levels above 1 kW are required to comply with a power flux density limit at all ground locations within 1 km of their base stations. The NPRM devotes considerable discussion to the 1 kW ERP power limit for upper 700 MHz band stations and concerns that increasing it could cause interference to Public Safety and Guard Band systems operating in the upper 700 MHz band. The NPRM states the FCC will not adopt any modifications to its power limits in this band, but asks what power flux density limits or other restrictions should be added to protect Public Safety and Guard Band systems and whether these restrictions should apply to all upper 700 MHz spectrum.

The NPRM asks whether the FCC should revise the 50 kW ERP limit on unauctioned lower 700 MHz spectrum, stating "commenters should discuss whether a need or demand exists for such high-powered transmissions in the band, and the impact, if any, a reduction in the power limit would have on current and future services and efficient utilization of this spectrum."

The FCC also asks whether the current power limit should be reduced, perhaps to as little as 1 kW, because of possible concern that the lower 700 MHz band PFD limit does not adequately limit adjacent channel interference from 50 kW ERP transmissions. "Commenters, in responding to this request for comment, should indicate what types of services they believe might benefit from and/or require the use of power levels lower than 50 kW ERP," the commission said. "Finally, commenters should address whether we (the commission) should, consistent with PCS and AWS, adopt a power limit of 2 kW ERP for rural areas only (without the need for a PFD limit) for base stations operating in the Lower 700 MHz Band."