Phil Kurz /
04.18.2012 03:40 PM
Originally featured on
FCC modifies antenna height, PSD and emission limits for fixed-TV-band devices

The FCC April 4, 2012, adopted the Third Memorandum Opinion and Order (MO&O) regarding commission rules for fixed-TV-band device use that addresses five petitions for reconsideration of its Second MO&O in the proceeding and modifies commission rules in three ways.

The modifications include: Increasing the maximum height above average terrain (HAAT) for sites where fixed devices may operate; Modifying the adjacent-channel emission limits to specify fixed rather than relative levels; and Increasing, slightly, the maximum permissible power spectral density (PSD) for each category of TV band device.

According to the MO&O, the changes will lower operating costs for fixed-television-band devices (TVBD) and give them the ability to provide greater coverage. The commission foresees the changes allowing fixed TVBDs to increase the availability of wireless broadband service in rural areas without increasing the risk of harmful interference to incumbent serves, such as television stations.

Commission rules allow fixed TVBD to operate with up to 1W transmitter power output and to use an antenna providing up to 6dBi of gain. They also require fixed devices to include geo-location capability to allow the device to find an unused portion of TV spectrum after checking in with a database of spectrum usage.

In the latest MO&O, the commission found that agency in its Second MO&O “generally established the appropriate balance between providing for operation of TV-band devices that will make new broadband services available to the public while protecting incumbent services in the TV bands from interference.” However, in the Third MO&O, there was merit in modifying the rules in a few ways.

First, the Third MO&O modifies the rules to set the maximum HAAT for fixed-device antennas at 820ft (250m) and maintaining the limit for fixed-device antenna height above ground level (AGL) at 98.4ft (30m). The agency also modified the required separation from digital or analog TV protected contour distances to mitigate the possibility of harmful interference resulting from the revised HAAT of unlicensed devices.

Second, it modifies the rules for adjacent channel emissions to specify a fixed value by adopting a fixed adjacent-channel emission limit for each category of TV-bands device that is equivalent to the current emission limit for devices operating at maximum power. Those operating at less than maximum permitted power are not required to suppress emissions below the fixed limits established.

The agency also declined to establish new requirements to protect wireless operations on channel 52.

The Third MO&O was released to the public April 5, 2012.

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