alokbhargava
Premium Pilot
Thank you.Ok for people who laugh off theories without keeping an open mind. It is a known problem!
Measuring the Effect of Helicopter Rotors on GPS Reception
Article Abstract
For instance
,
when a GNSS receiver is placed near rotating bodies
,
the signal undergo complex and non-stationary effects
called Rotor Blade Modulation (RBM).
The example you are quoting here is of a single rotor heli with GPS receiver minuted underneath or close to it. It's behavior will be totally different than of multi rotor system as we have in P3. In a single rotor helis the GPS radio signal is affected by metallic blades and effectively a signal is injected whose frequency is related to the rotor speed. The problem in such cases is that the amplitude of this modulating frequency signal is very high and needs special design to filter it out. In case of multi rotor system, the effect of rotating blades is very small if the GPS receiver is mounted in the center as is the case of P3. Also as the rotating blades position is not considerable higher than the GPS receiver, the influence of rotating blades is thus negligible on the main radio frequency signal. Did you notice that GPS receiver is positioned at a relatively higher position?
Secondly, the DJI cf blades are not fully metallic, their influence is further reduced.
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