I am currently testing internal antenna options for 2.4 GHz applications. The only accessible location for the antenna is the metal protector side of a cooling fan. The antenna sits about 2 cm above the plastic blades. I wonder if the rotating blades interfere with the near field EM field and reduce far field reading distance?

 

The Plastic Fan-Blades will cause no effects at all,
but the metal-Fan-Guard will have a definite negative effect on the broadcasting and reception-patterns,
possibly blocking all traffic to/from the Antenna.
( Pictures required )
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Dielectrics, such as plastic, have little effect on EM waves.
Conductors, (metals and graphite), have a significant effect, and can block, attenuate, or reflect the wave, depending upon its configuration.

 

Depending on the antenna design, mounting it on a metal surface may either improve or impair the function. If it is a quarter wave end fed antenna designed to be on a ground plane then it will perform quite a bit better. If it is a center fed dipole it may noyt work well at all