SBE Opposes Department of Defense Uplinks in 2 GHz BAS Band
November 17, 2003
SBE filed comments opposing the FCC's plans to move 11 Department of Defense (DoD) uplinks into the broadcast auxiliary band at 2025-2110 MHz. SBE explained the move "would pose a serious interference threat to the ability of broadcasters to continue to use these frequencies for electronic news gathering (ENG) in the vicinity of the DoD uplinks." The SBE comments raised concerns about interference in several markets. DoD uplinks near Denver, Colorado Springs, and Orlando were shown to either have a line of site path or a path with insufficient obstruction loss to avoid interference to ENG sites in these markets, although the uplink near Albuquerque did appear to be adequately shadowed from the Sandia Crest ENG receive sites.
The SBE filing pointed out that under the rules proposed in the NPRM, a DoD uplink would be allowed up to 70 dBm effective isotropic radiated power (EIRP) at horizontal plus three times the elevation angle from zero to five degrees. However, based on the high transmitter power outputs (between 100 and 10,000 watts) and the use of a 10-meter parabolic uplink dish with a gain of around 45 dBi, the main beam EIRP at higher power would be between 95 and 115 dBm. SBE estimated side lobes from a 10 meter uplink dish would be no more than 60 dB down, allowing EIRPs outside the main beam at levels between 35 and 55 dBm, compared with 60 dBm EIRP from a typical ENG truck. At these levels, the uplink could interfer with analog ENG reception and, at the higher level, would pose problems for digital ENG as well.
Inaccuracies in the coordinates of the DoD uplink locations made interference analysis more difficult for SBE. In the case of the Laguna Peak uplink near Los Angeles, the coordinates in the NPRM showed it in a 12-foot AMSL creek bed. SBE was able to find out from DoD personnel that the uplink was instead on top of a 1,457 foot AMSL mountain peak, which clearly has more potential to cause interference to ENG operations in the Los Angeles area.
If the FCC, DoD or NTIA wanted to analyze the impact of the DoD uplinks on broadcast ENG operations, it would have difficult doing this as the current version of FCC Form 601 only allows a TV pickup station to specify one set of receive coordinates, even though the station may use many sites, and limits the receiving antenna height to 6.1 meters (20 feet) AGL, even ENG sites are typically much higher.
SBE proposed a set of conditions under which DoD use of the 2025-2110 MHz BAS band would be acceptable:
1. In general, only DoD uplinks located outside TV markets 1-50 should be eligible (only if a DoD uplink has unusually favorable terrain shielding should it be considered as a candidate for conversion to 2 GHz even though located in a top-50 TV market);
2. All 2 GHz TV BAS links and TV pickup stations in the TV market where the uplink is located must be using digital modulation;
3. The DoD uplink antenna must have side lobes that are at least 95 dB down;
4. The DoD uplink must only transmit for elevation angles of 10 degrees or higher;
5. As proposed in the NPRM, each uplink operation must have been deemed by SBE to have been successfully frequency coordinated;
6. A "hot line" telephone number must be provided to SBE, and staffed, at all times when the uplink is transmitting, so, in the event of interference, said interference can be promptly made known to the DoD uplink in question and corrective action taken. SBE believes that this requirement should also apply to any secondary DoD operations, as proposed in Footnote 46 and Paragraph 38 of the NPRM.
For more information, see the SBE comments and the link to the directory of figures available on this page. Details on the original NPRM can be found in the July 14 RF Report.