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Transponder antenna in rag/tube aircraft

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peter(at)mather.com
Guest

Posted: Sat Oct 06, 2007 9:34 am Post subject: Transponder antenna in rag/tube aircraft

I'm getting reports of very poor reception of my  transponder in my Piper Colt. I've been through chaper 13 of the conection and  can't really find anything that addresses this sort of airframe. 

  

 Questions: I assume I should use a ground plane of  5 1/2" diameter as per a composite aircraft? Do I make sure the ground plane is  isolated from the metal frame or bond it to it? Does it matter how close the  ground plane is to the metal structure?

  

 Any help gratefully received

  

 Thanks

  

 Peter

   [quote][b]

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nuckolls.bob(at)cox.net
Guest

Posted: Sun Oct 07, 2007 2:38 pm Post subject: Transponder antenna in rag/tube aircraft

At 06:28 PM 10/6/2007 +0100, you wrote:



 	  Quote: 	
		  I'm getting reports of very poor reception of my transponder in my Piper 

Colt. I've been through chaper 13 of the conection and can't really find 

anything that addresses this sort of airframe.



Questions: I assume I should use a ground plane of 5 1/2" diameter as per 

a composite aircraft?


	


    Yes . .



 	  Quote: 	
		    Do I make sure the ground plane is isolated from the metal frame or bond 

 it to it?


	


   Doesn't matter it works as advertised even

   when completely isolated from the metallic

   airframe.



 	  Quote: 	
		    Does it matter how close the ground plane is to the metal structure?


	


   No



   What's the largest area "window" you can see in the

   tube structure on the side of the fuselage?



   Here's an excerpt from the Aircraft Spruce

   catalog at:



http://aircraftspruce.com/pdf/2008Individual/Cat08532.pdf



ANTENNAS FOR COMPOSITE AIRCRAFT

MODEL 5 - This transponder/DME antenna is an

etched copper clad epoxy circuit board dipole

that is designed to be installed inside non-conductive

aircraft without need for the additional

installation of a ground plane. The dimensions

are 6" x 7" and it can be installed in the aft

fuselage or the wings with the 6" dimension

vertical.VSWR is less than 1.2:1 over bands of 1032 to 1090 Mhz.

.......................................................P/N 11-21005 

.........$88.50



   If you could mount this to the inside surface

   of the fabric, 6" dimension vertical and 6"

   of clearance all around edges, this might

   perform much better and be easier to install

   than a ground plane on the bottom.



   Bob . . .

        ----------------------------------------

        ( "Problems are the price of progress. )

        ( Don't bring me anything but trouble. )

        ( Good news weakens me."               )

        (              -Charles F. Kettering-  )

        ----------------------------------------

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Peter H

Joined: 20 Mar 2007
Posts: 197

Posted: Sun Oct 07, 2007 3:41 pm Post subject: Transponder antenna in rag/tube aircraft

Related question please.

In my glass hull I fitted the transponder antenna about 4" inside the

perimeter of the circular VHF ground plane ie it shares this ground plane.

Is that a No-No?

Thanks

Peter H 



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echristley(at)nc.rr.com
Guest

Posted: Sun Oct 07, 2007 10:12 pm Post subject: Transponder antenna in rag/tube aircraft

Robert L. Nuckolls, III wrote:

 	  Quote: 	
		   

 <nuckolls.bob(at)cox.net>



 At 06:28 PM 10/6/2007 +0100, you wrote:



> I'm getting reports of very poor reception of my transponder in my 

> Piper Colt. I've been through chaper 13 of the conection and can't 

> really find anything that addresses this sort of airframe.

>

> Questions: I assume I should use a ground plane of 5 1/2" diameter as 

> per a composite aircraft?



 Yes . .



> Do I make sure the ground plane is isolated from the metal frame or 

> bond it to it?



 Doesn't matter it works as advertised even

 when completely isolated from the metallic

 airframe.



> Does it matter how close the ground plane is to the metal structure?



 No



 What's the largest area "window" you can see in the

 tube structure on the side of the fuselage?



 Here's an excerpt from the Aircraft Spruce

 catalog at:



 http://aircraftspruce.com/pdf/2008Individual/Cat08532.pdf


	


Bob, I could fit that antennae in my project, but I've been looking that 

the one described by Matjaž Vidmar at 

http://lea.hamradio.si/~s53mv/avionics/avionics.html , specifically 

http://lea.hamradio.si/~s53mv/avionics/tranant.html



It's an 'annular' (is that correct) antennae, and the advertised benefit 

is that it concentrates more of the energy in one direction. In my case 

it will be facing down, so I'd expect the transponder reach the ground 

better. Do you have any experience with this sort of antennae? Will it 

work? Are there serious gotcha's that I haven't a clue about?

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nuckolls.bob(at)cox.net
Guest

Posted: Mon Oct 08, 2007 8:32 am Post subject: Transponder antenna in rag/tube aircraft

At 09:40 AM 10/8/2007 +1000, you wrote:



 	  Quote: 	
		  

<peterjfharris(at)bigpond.com>



Related question please.

In my glass hull I fitted the transponder antenna about 4" inside the

perimeter of the circular VHF ground plane ie it shares this ground plane.

Is that a No-No?

Thanks

Peter H


	


   it will probably be fine.



   Bob . . .

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Peter H

Joined: 20 Mar 2007
Posts: 197

Posted: Mon Oct 08, 2007 1:23 pm Post subject: Transponder antenna in rag/tube aircraft

Thanks again Bob !

Peter H



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