RFI mitigation on mobile base stations around FAST

After five and a half years construction, the main structure of Five-hundred-meter Aperture Spherical radio Telescope (FAST) has been completed in September 2016. Meanwhile, a Radio Quiet Zone (RQZ) with radius 30 km has also been established. In order to evaluate the Radio Frequency Interference (RFI) influence from the mobile base stations within radius 5 km (the restriction zone of RQZ) around FAST, several measurements have been carried out when these stations were closed temperately. Comparing the RFI measurement results before and after the closure of these stations, the interference has been decreased more than 30 dB. Since November 1 2016, all the mobile base station within the restriction zone of FAST RQZ have be closed permanently to avoid the risk of the receiver saturation due to the interference coming from these stations.