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ELT antenna location

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cbirdsall6(at)cox.net
Guest

Posted: Sun Jun 23, 2013 11:39 pm Post subject: ELT antenna location

I'm putting a 406MHz ELT (ACK E-04) in my Piper Cherokee in place of 

dead OE Narco.



One of the statements in the installation manual - and in other 

references such as AC43.13-2 and antenna manufacturers - says that the 

ELT antenna should be at least 36 inches from a Com antenna. Key word:  

Should.



The original mount for the factory-installed Narco ELT antenna is 18 

inches away from the Com 2 antenna.  A quick cruise around the airport 

found that most of the Pipers with dual coms have a similar setup. I 

don't want to move the Com 2 antenna because that will start a vortex 

I'd rather avoid for the time being.  Venerable but still functioning 

avionics package supported by an antenna farm limits my options.



I realize there are coupling factors with antennas placed within a 

half-wavelength of each other.  I called the manufacturer and asked - 

and was told they strongly recommend maintaining 3 feet distance, but 

they also shoved lots of RF at the antenna/ELT combo during testing and 

saw no ill effects.



So the questions are:

Am I going to have to move the Com 2 antenna?

What are the risk factors if I leave the antenna locations as they are?

Thanks,



Chuck

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billp(at)wwpc.com
Guest

Posted: Mon Jun 24, 2013 6:38 am Post subject: ELT antenna location

You're going to have to replace the factory ELT antenna anyway. The 406 

ELTs come with antennas that work on both 121.5 and 406. The old antenna 

will only be effective on 121.5. Are you saying that you have to move 

the Com 2 antenna because there's no place on the upper fuselage that's 

3' away? Or are you saying you don't want to move the ELT antenna position?



In any case, the biggest problem of having the 2 antennas in such close 

proximity is going to be that they will influence each others radiation 

patterns and you'll find nulls in the coverage in certain directions. 

I'm a little surprised that the antennas got positioned that close to 

begin with but it's hard to find enough good places on small airplanes.



Bill



On 6/24/13 12:38 AM, Chuck Birdsall wrote:

 	  Quote: 	
		   

 <cbirdsall6(at)cox.net>



 I'm putting a 406MHz ELT (ACK E-04) in my Piper Cherokee in place of 

 dead OE Narco.



 One of the statements in the installation manual - and in other 

 references such as AC43.13-2 and antenna manufacturers - says that the 

 ELT antenna should be at least 36 inches from a Com antenna. Key 

 word:  Should.



 The original mount for the factory-installed Narco ELT antenna is 18 

 inches away from the Com 2 antenna.  A quick cruise around the airport 

 found that most of the Pipers with dual coms have a similar setup. I 

 don't want to move the Com 2 antenna because that will start a vortex 

 I'd rather avoid for the time being. Venerable but still functioning 

 avionics package supported by an antenna farm limits my options.



 I realize there are coupling factors with antennas placed within a 

 half-wavelength of each other.  I called the manufacturer and asked - 

 and was told they strongly recommend maintaining 3 feet distance, but 

 they also shoved lots of RF at the antenna/ELT combo during testing 

 and saw no ill effects.



 So the questions are:

 Am I going to have to move the Com 2 antenna?

 What are the risk factors if I leave the antenna locations as they are?

 Thanks,



 Chuck

- The Matronics AeroElectric-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?AeroElectric-List

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