Radio transmission can be directional. If you put a directional antenna on a drone and direct it to a satellite it would be close to impossible to detect it from below the drone. You might have a chance from a aircraft close and above the drone but that is hard to do
Transmission to the drone do not need to be directed to it bout could cover countries or continents and if they are encrypted the would not help in detecting the drone.
I would be easier to intercept if you had electronic intelligence satellite in the correct position in space but they are rare and few countries have any.
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