Elliptical C-band Uplink Antennas

Via Doug Lung’s RF Report:

In some cases, it isn’t possible to install an uplink dish that meets the FCC off-axis antenna pattern envelope. In the past, the FCC allowed operation of uplinks with non-compliant antennas upon a showing by the licensee that the effective isotropic radiated power (EIRP) would be reduced enough to keep the energy in side lobes below the level that would have existed using an uplink with a compliant dish at maximum power. This required a detailed engineering showing that often slowed FCC processing.

In the Eighth Report and Order and Order on Reconsideration (FCC 08-246), the FCC adopted an off-axis EIRP envelope approach as one method for applicants to apply for fixed satellite service (FSS) Earth stations using small antennas operating on conventional C and Ku-band frequencies.

It states, "This off-axis EIRP approach gives earth station applicants the flexibility to reduce their power levels to compensate for a small antenna diameter. Thus, using these envelopes as criteria for licensing should enable us to license more earth station applications routinely, expediting the provision of satellite services to consumers and enhancing the types of services available, without increasing the likelihood of harmful interference to adjacent satellite operators or to terrestrial wireless operators."

The Order adopts rules that facilitate the use of elliptical C-band uplink antennas. While the new rules do not specifically state that the major axis of the elliptical antenna be aligned with the geo-stationary orbit plane, the Order notes that "that starting the off-axis EIRP envelope at 1.5 degrees off-axis within the GSO orbital plane, and at 3.0 degrees outside that plane, has the same effect as requiring elliptical antennas to be aligned with the GSO plane in most cases."

The Satellite Industry Association (SIA) claimed that it is not possible to develop an off-axis EIRP envelope for analog video signals because the power density of such signals fluctuates. SES Americom opposed new analog regulations because the current rules are working well. The FCC decided to retain the current regulatory framework for analog services at this time. It dropped plans for eliminating analog video transmission over satellite entirely, noting, "The record in this proceeding has shown convincingly that requiring the transition from analog to digital video transmissions proposed in the Third Further Notice would be unreasonably expensive and burdensome."


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