While most broadcast engineers know Society of Broadcast Engineers (SBE)
for its certification of broadcast operators and engineers, it continues to play an important role in protecting broadcast auxiliary service (BAS) frequencies.
Recently the organization filed a Petition for Reconsideration
of FCC International Bureau Docket 02-364 relating to an ancillary terrestrial component (ATC) for the Mobile Satellite Service (MSS). In the petition, SBE proposed a new, all digital band plan for the 2.5 GHz BAS band, including channels A8 (2450-2467 MHz), A9 (2467-2483.5 MHz) and the grandfathered channel A10 (2483.5-2500 MHz). Under the proposed plan, the 2.5 GHz broadcast auxiliary band would continue to consist of three channels, but they would be limited to 12 MHz bandwidth located between 2450 MHz and 2486 MHz. Since the MSS ATC allocation doesn't start until 2487.5 MHz, this would allow a 1.5 MHz guard band between BAS and MSS ATC.
While SBE conceded that frequency coordination between channel 10 fixed-link BAS stations and MSS ATC base stations might be possible if costly ultra-high performance, shrouded receiving antennas were used by the BAS station, it could not "envision such techniques as ever working for mobile/portable/itinerant grandfathered Channel A10 Pickup operations, where heavy, large-diameter parabolic dish antennas are completely impractical for electronic news gathering (ENG) and man pack applications." This could be a problem for the MSS ATC stations, as 78 or the 109 grandfathered TV BAS channel A10 licenses are for TV Pickup stations and their operations are co-primary with the MSS ATC operations. The SBE band plans eliminates this problem by completely moving TV BAS channel A10 out of the MSS ATC spectrum.
SBE explained the plan provides other benefits as well. The FCC extended the lower band edge for the Broadband Radio Service (formerly ITFS/MMDS) spectrum from 2500 MHz to 2496 MHz, making the lower 4 MHz co-channel with TV BAS channel A10. Under SBE's plan to shrink the 2.5 GHz BAS band, this overlap would disappear.
In addition to benefiting broadcasters, the new band plan would also benefit public safety stations authorized to use the 2450-2500 MHz band. In addition to the reduction in interference, the digital modulated channels could be encrypted. SBE notes, "if Public Safety operations do nothing, and continue to attempt to operate with analog modulation between 2,487.5 and 2,500 MHz, before long they will find themselves in a sea of mutual interference, and the Commission will have a new public safety interference problem to deal with."
For more information on the SBE proposal, including details on reimbursement to public safety and BAS stations for converting to the new 2.5 GHz band plan, please refer to the SBE Petition for Reconsideration