Broadband Radio Service and Educational Radio Service stations are limited to a maximum effective isotropically radiated power of approximately 2 kW for transmissions occupying the full channel. Until last week, OP LLC, a subsidiary of Crown Castle, was also limited to 2 kW peak EIRP for its Modeo service in the 1670-1675 MHz band. In Memorandum Opinion and Order FCC 07-16, released Monday, the FCC allowed Crown Castle to operate with peak EIRP up to 20 kW in non-rural areas and 40 kW in rural areas using its proposed 5 MHz bandwidth DVB-H technology.
Crown Castle said that the power increase would enable it to construct fewer base stations, allowing a more efficient and faster deployment of service and that the higher power would reduce "dead-spots" and enhance in-building coverage. The FCC agreed that the power increase was justified, as long as Crown Castle protected GOES weather satellite co-primary operations in the band. Crown Castle does not share frequencies used for NOAA and GOES public downlinks, which operate between 1685 and 1707 MHz.
The 1670-1675 MHz spectrum used by Crown Castle for Modeo is shared with the GOES earth stations located at Wallops Island, Va. and Fairbanks, Alaska. The FCC waiver of the power limits requires Crown Castle to fully protect these facilities, as well as the GOES earth station located at Greenbelt, Md. when it is active. Crown Castle must also consult with and protect radio astronomy facilities within 185 kilometers of the facilities. Two of the four hydroxyl line frequencies, 1665 MHz and 1667 MHz are near the spectrum Crown Castle will be using. The National Weather Service currently operates radiosondes in the 1675-1683 MHz band. The FCC required Crown Castle to coordinate with NWS the operation or modification of any base station using more than 2 kW EIRP within 1.3 kilometers of any NWS Upper Air Site. Crown Castle agreed to comply with this coordination requirement.
It will be interesting to see how Crown Castle achieves an EIRP of up to 40 kW at 1.6 GHz, as this is 20 times the power level currently being used for ERS/BRS stations. While high gain antennas can be used at 1.6 GHz, any gain comes with increased directivity, reducing the area a station can serve once most of the power is below the radio horizon. We might get some clues at NAB 2007 from the manufacturers who supply them with the transmitters!
