New Starlink consumer key with smaller antenna seems in FCC submitting
Space Exploration Technologies Corp. (SpaceX) has filed an application with the Federal Communications Commission (FCC) to test a new variant of its user terminal for the company’s Starlink satellite internet constellation. The application was submitted to the Commission’s Office of Experimental Testing (OET) yesterday and lists different specifications for the terminal’s receiving antenna compared to previous submissions from SpaceX. The Starlink terminals are used by users to connect to the orbiting satellites, which then relay the data to one of the many ground stations spread across the continent of the United States.
Starlink user terminal for testing various parameters for antenna reception
In its motion, SpaceX asks the FCC to grant it temporary permission to test five new user terminals in California, Colorado, Texas, Utah and Washington. These terminals use the same uplink and downlink frequencies as those used by the Starlink beta testers.
Although they use the same frequencies, the parameters for their transmit and receive antennas are different from those that have popped up in SpaceX’s previous FCC applications. Because of these differences, it is clear that while the company is not testing a brand new design for its Starlink user terminals, it is testing the impact of optimizing key specifications on performance.
The consumer terminals have two separate antenna parameters, one for sending signals and one for receiving them. In the latest FCC filing, the parameters for the transmit antenna are similar to those in a previous SpaceX filing asking regulators to test Starlink terminals on vehicles in Redmond, Washington.
Specifications of the Starlink user terminals for testing on mobile platforms. Picture: FCC 0562-EX-ST-2021
The parameters of the transmitting antenna (TX), namely the gain, the half width, the effective isotropic radiation power (EIRP) and the effective radiation power (ERP) remain unchanged in the new applications compared to the application for the vehicle test.
However, the parameters for the radiating (RX) antenna are different, indicating the different nature of the two tests. In the Starlink user terminal, the transmitting antenna is responsible for sending the user data to the orbiting satellites and the receiving antenna is responsible for receiving the data.
The first thing to note is that the area of the receiving antenna is smaller in the new shelf, which then corresponds to a reduction in its key parameters. First of all, its gain, which describes its ability to convert the received signals into electrical power, is lower. While on the surface it does appear to be detrimental to performance, that corresponds well with SpaceX’s recent victory at the FCC, which allowed it to lower satellite altitudes.
The technical parameters of the new shelf that the user terminals designate as “new”. Picture: FCC 0916-EX-ST-2021
A lower gain reduces the range of the antenna, but increases the area covered. In essence, the new tests should allow SpaceX to determine whether the user terminals can receive signals from a wider area compared to those mounted on a moving vehicle.
The second parameter that differs is the figure of merit. Measured as decibels divided by Kelvin, this measures an antenna’s gain in relation to the noise received. For the test with moving vehicles, the user terminal had a noise temperature of 3.25 Kelvin, lower than that of the new terminal of 3.7 K. This temperature is not a physical measured value; instead, it is determined by the temperature change in a hypothetical resistor due to antenna noise.
Finally, the emission labels are the same for both terminals, which suggests that the above differences are minor. Interestingly, however, the name is different for another submission in which SpaceX asks the commission authority to test the dishes on the marine platform. An emissions qualifier is used by the FCC and other agencies to describe the bandwidth of the signals, and the one used by the marine platform indicates a lower bandwidth.