[time-nuts] Boeing 787 GPS reception trouble

Mark Sims holrum at hotmail.com
Mon Jun 2 11:52:24 EDT 2014


I build and fly large model rockets.  Many use carbon fiber in their construction.   I can tell you that carbon fiber does conduct electricity... not quite as well as pure metals,  but pretty darn good... and the conduction is anisotropic (better conduction along the fibers than across their diameter...  and the same for thermal conductivity).   And that it makes a GREAT RF shield.   

Most of my rockets have tracking transmitters in them... most at around 220 Mhz   A single layer of 5 oz carbon cloth around a phenolic body tube can almost totally block the tracking signal of a transmitter that has a 20+ mile open-air range.  Once inside the carbon wrapped airframe,  it has a range of a couple hundred feet.  You get the tracking signal only when the rocket separates and the tracking transmitter is extracted from the airframe.   An interesting observation is that putting the transmitter in an aluminum airframe has little effect on its range.    It seems that that the "semi-condcutive" properties of the carbon fiber is responsible for its RF properties. 		 	   		  


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