This random webpage claims that the (probably "a") satellite uplink frequency is "13.75 - 14.5 GHz". So you would have to dig up a downconverter that works in t

This random webpage claims that the (probably "a") satellite uplink frequency is "13.75 - 14.5 GHz". So you would have to dig up a downconverter that works in that band. Perhaps if the drone was overhead there might be enough signal that makes it to the ground to detect. If this became popular it might turn out to be worth the bother to equip drones with receivers to detect the local oscillator leakage from such early warning systems.