Phil Kurz /
03.24.2009 08:14 AM
Originally featured on BroadcastEngineering.com
CBA asks FCC for additional protection from TV band device first adjacent-channel interference
The Community Broadcasters Association last week asked the FCC to reconsider a portion of its Report and Order authorizing unlicensed TV band devices to protect LPTV and Class A stations from such devices operating on first adjacent channels.
In the association’s view, the FCC action authorizing unlicensed devices appears to have been based on the notion that LPTV and Class A will be viewed only via digital TV receivers when, in fact, most of these stations will continue to be on the air with their analog signal and have no deadline established to transition to digital transmission.
According to the filing, analog TV receivers “have different interference-rejection characteristics” than DTV receivers, and, thus, LPTV and Class A stations require greater protection. The association takes issue with the commission using the ATSC Standard A/74 when it set power limits for the newly authorized unlicensed devices. “‘ATSC’ is, of course, the digital television standard,” the filing said. “No mention is made of any analog receiver standard or the performance characteristics of analog, even though the commission clearly understands that viewers will be watching analog LPTV stations on analog receivers for some years to come.”
As a result of using just one receiver standard, the commission set a power limit for unlicensed devices of 40mW that doesn’t meet minimum distance separation requirements from first adjacent-channel LPTV stations, regardless of whether the station is transmitting in analog or digital.
The association asked the commission to reduce the power limit for unlicensed devices by 9dB for those operating on the upper first adjacent channel and by 14dB for those on the lower first adjacent channel where minimum mileage separations aren’t met. The CBA filing also requested the commission increase the minimum mileage separation from where the station being protected is transmitting an analog signal.