12.03.2004 08:00 AM
Originally featured on BroadcastEngineering.com
SBE asks FCC to reconsider order allowing defense uplinks in TV BAS frequency

The Society of Broadcast Engineers filed a petition with the FCC Nov. 24 asking the commission to reconsider a Report and Order regarding the relocation of Department of Defense uplinks to the 2025MHz to 2110MHz bands used for broadcast auxiliary services (BAS) operations, such as ENG transmission.

In the petition, the SBE said the commission’s characterization in the Report and Order that the society agreed that up to 11 defense satellite sites could share 2GHz TV BAS frequencies if BAS users convert to COFDM is a “gross and serious distortion.”

The filing indicates that relocating the military satellite communications would only be successful in the BAS frequencies if COFDM were used and if side lobe suppression was improved by about 30dB by adding “a ‘pie plate’ shroud around the periphery of the uplink antenna, lined with an RF-absorbing material.”

Together the steps would be likely to improve the ratio of desired to undesired signals between the desired BAS ENG receive-only signal and the undesired military uplink signal by about 60dB. The society asked the commission to state explicitly that any military uplink in the TV BAS band in question must upgrade side lobe suppression by at least -90dBc.

The petition asserted that use of berms to mitigate interference from military uplink sites would be impractical. In some cases, such shielding berms would need to be 100ft to 200ft tall to protect reception of low-angle ENG microwave transmissions.

Additionally, the SBE asked the commission to confirm that the Defense Department uplinks protect fixed link 2GHz TV BAS antennas used for STLs and inter-city relays and ENG receive-only sites, which is “far more difficult” because they are omnidirectional or remotely steerable.

Finally, the SBE objected to language in the Report and Order specifying the FCC and National Telecommunication and Information Administration as arbiters to resolve “those rare situations where no reasonable coordination can be negotiate.”

According to the society, this language implies that the Defense Department “will be permitted to do an ‘end run’ around the frequency coordination process, leaving out the local broadcaster.”

For more information, visit www.sbe.org.

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