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Antenna static discharge protection

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enginerdy(at)gmail.com
Guest

Posted: Fri Jul 01, 2011 4:08 pm Post subject: Antenna static discharge protection

I'm curious if anyone has experience with protecting RF circuits from

static buildup on exposed antennas during flight.



What is required? Assuming the circuit can only withstand small

voltages (10-20V), is a 100V ceramic blocking capacitor with a 1Meg

drain resistor sufficient? Do you need some sort of diode or gas

discharge device?



Has anyone done or seen research on how quickly voltages can rise (or

fall) on an antenna element in flight?



I'm looking at ham radio-type stuff here, so don't assume a nice,

robust nav/com radio 



Thanks,

Daniel

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nuckolls.bob(at)aeroelect
Guest

Posted: Fri Jul 01, 2011 5:24 pm Post subject: Antenna static discharge protection

At 07:04 PM 7/1/2011, you wrote:

 	  Quote: 	
		  



I'm curious if anyone has experience with protecting RF circuits from

static buildup on exposed antennas during flight.


	


   What kinds of circuits?  Radios designed for the

   aircraft environment are already so protected.



 	  Quote: 	
		  What is required? Assuming the circuit can only withstand small

voltages (10-20V), is a 100V ceramic blocking capacitor with a 1Meg

drain resistor sufficient? Do you need some sort of diode or gas

discharge device?



Has anyone done or seen research on how quickly voltages can rise (or

fall) on an antenna element in flight?


	


    Not sure about rates of rise but intensities can

    be very high . . . 100Kv type high

 	  Quote: 	
		  I'm looking at ham radio-type stuff here, so don't assume a nice,

robust nav/com radio 


	


   Voltages are high, but energies and currents are

   very low. A simple inductor across the antenna lead

   to ground having negligible conductivity at frequencies

   of interest are quite sufficient.



   A 1000 ohm resistor across a 50 ohm transmission

   line would have negligible effect on swr and/or

   lost energy . . . and a profound effect on buildup

   of precipitation static.



   Bob . . .

   Bob . . .

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enginerdy(at)gmail.com
Guest

Posted: Fri Jul 01, 2011 7:46 pm Post subject: Antenna static discharge protection

 	  Quote: 	
		    Voltages are high, but energies and currents are

  very low. A simple inductor across the antenna lead

  to ground having negligible conductivity at frequencies

  of interest are quite sufficient.

 

  A 1000 ohm resistor across a 50 ohm transmission

  line would have negligible effect on swr and/or

  lost energy . . . and a profound effect on buildup

  of precipitation static.


	


Ah! I hadn't considered a shunt inductor!



Thanks for the info! If anyone else knows where to find data on in flight ESD I'd still love to see it.

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nuckolls.bob(at)aeroelect
Guest

Posted: Sat Jul 02, 2011 6:32 am Post subject: Antenna static discharge protection

At 10:40 PM 7/1/2011, you wrote:

 	  Quote: 	
		  


	


 	  Quote: 	
		  Ah! I hadn't considered a shunt inductor!



Thanks for the info! If anyone else knows where to find data on in 

flight ESD I'd still love to see it.


	


    We had a big shake-up at Beech about 25 years

    ago to deal with some static discharge wick issues

    on the fleet. There are pretty simple bench tests

    to test the relative effectiveness of a static

    wick. I'm aware of no flight test data . . . you

    might poke around in the patents  (freepatentsonline.com)

    and NASA documents.

   Bob . . .

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