Currents can be perfectly well induced in the motors themselves, by the variable magnetic field of an electromagnetic wave.
Any electromagnetic wave has both an electric field and a magnetic field, hence its name.
An antenna can be made from either a straight wire sensitive to the electric field or from a loop of wire sensitive to the magnetic field.
The only reasons why a motor is usually a bad antenna is that it should have a case with good shielding properties (i.e. the magnetic circuits have only small gaps) and the high inductances of its windings act as low-pass filters for high-frequency induced currents, like those of a microwave transmitter.
There exist electric motors with very low inertia of the moving parts (to enable high accelerations), where the rotor does not have any ferromagnetic material and the stator has large gaps for the rotor. Such motors can be much more efficient antennas than standard motors, but such motors are not used in drones.
All the cheap radios for under 30 MHz signals used antennas made of a ferrite bar with a coil on it, very similar to a motor winding, except that the magnetic circuit had a much greater gap than in a motor, because they were more sensitive at small sizes than antennas sensitive to the electric field.
Moreover, brushless motors do not have an aluminum rotor. You are thinking about AC induction motors. Induction motors do not have brushes, but nobody calls them brushless, because they never had brushes. Only DC motors are called brushless, because their classic variant had brushes, which are replaced by power transistors in brushless motors.
The aluminum rotor of induction motors is normally inside, not outside. The inverted construction is rare.
Both induction motors and brushless motors have windings only on the stator, which is the external part in the normal motor structure, and those are equally susceptible to variable magnetic fields, except that they are usually bad antennas for the reasons mentioned above, especially at microwave frequencies.
In an ideal motor, the stator is not an electrical conductor (which is actually the case for ferrite stators), so it has no shielding properties for electric fields, but it has shielding properties for the magnetic field, if the gaps in its magnetic circuit are small.
Almost all quadcopter brushless motors are constructed as “outrunners,” with a fairly thick, sturdy aluminum motor bell (rotor!) with strong permanent magnets glued inside of it and the stator in the center. I agree that they are not immune to RF but at high frequencies it will require a really comical amount of power to do anything to one.
Any electromagnetic wave has both an electric field and a magnetic field, hence its name.
An antenna can be made from either a straight wire sensitive to the electric field or from a loop of wire sensitive to the magnetic field.
The only reasons why a motor is usually a bad antenna is that it should have a case with good shielding properties (i.e. the magnetic circuits have only small gaps) and the high inductances of its windings act as low-pass filters for high-frequency induced currents, like those of a microwave transmitter.
There exist electric motors with very low inertia of the moving parts (to enable high accelerations), where the rotor does not have any ferromagnetic material and the stator has large gaps for the rotor. Such motors can be much more efficient antennas than standard motors, but such motors are not used in drones.
All the cheap radios for under 30 MHz signals used antennas made of a ferrite bar with a coil on it, very similar to a motor winding, except that the magnetic circuit had a much greater gap than in a motor, because they were more sensitive at small sizes than antennas sensitive to the electric field.
Moreover, brushless motors do not have an aluminum rotor. You are thinking about AC induction motors. Induction motors do not have brushes, but nobody calls them brushless, because they never had brushes. Only DC motors are called brushless, because their classic variant had brushes, which are replaced by power transistors in brushless motors.
The aluminum rotor of induction motors is normally inside, not outside. The inverted construction is rare.
Both induction motors and brushless motors have windings only on the stator, which is the external part in the normal motor structure, and those are equally susceptible to variable magnetic fields, except that they are usually bad antennas for the reasons mentioned above, especially at microwave frequencies.
In an ideal motor, the stator is not an electrical conductor (which is actually the case for ferrite stators), so it has no shielding properties for electric fields, but it has shielding properties for the magnetic field, if the gaps in its magnetic circuit are small.