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Transponder antenna

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mike(at)vision499.com
Guest

Posted: Sat Nov 11, 2017 4:15 pm Post subject: Transponder antenna

In a composite aircraft does the transponder antenna have to be outside the fuselage?

 

If it can be inside how do you make a ground plane?

 

Is it OK to be close to the COM antenna

 

Thanks

 

Mike

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rlborger(at)mac.com
Guest

Posted: Sat Nov 11, 2017 5:17 pm Post subject: Transponder antenna

Mike,



FWIW, I used the Archer transponder antenna for composite aircraft.   It is a full wave antenna that doesnâ€™t require a ground plane.   Works great.    

Having a warm body close to a comm antenna will distort the transmission pattern.   But it would be difficult to say how much.  Better if it were some distance away.  I have my comm antenna in the tail.   

Blue skies & tail winds,

Bob Borger 



Sent from my iPhone



On Nov 11, 2017, at 18:13, mike(at)vision499.com (mike(at)vision499.com) wrote:

  <![endif]-->   <![endif]-->

In a composite aircraft does the transponder antenna have to be outside the fuselage?

 

If it can be inside how do you make a ground plane?

 

Is it OK to be close to the COM antenna

 

Thanks

 

Mike



  	          		Virus-free. www.avast.com 		 	 [url=#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2] [/url]

Airdog77

Joined: 24 Nov 2013
Posts: 80
Location: Northern Virginia

Posted: Sun Nov 12, 2017 2:00 am Post subject: Re: Transponder antenna

Mike,



 	  Quote: 	
		  In a composite aircraft does the transponder antenna have to be outside the fuselage? 	


No, none of the antennas have to be outside the aircraft.



 	  Quote: 	
		  If it can be inside how do you make a ground plane? 	


Check out the Advanced Aircraft Electronics L2 Transponder Antenna made specifically for composite aircraft, no ground plane required and costs less than $100.  



http://www.aircraftspruce.com/catalog/avpages/antennasystems1.php?clickkey=4083



 	  Quote: 	
		  Is it OK to be close to the COM antenna? 	
 

If you mean the transponder antenna, from my understanding no.  I think you want to be as far away as possible, within reason.  Different antennas may have different requirements.



Cheers,

Wade

_________________
Airdog
Wade Parton
Building Long-EZ N916WP
www.longezpush.com

donjohnston

Joined: 13 Dec 2009
Posts: 231

Posted: Sun Nov 12, 2017 5:02 pm Post subject: Re: Transponder antenna

 	  mike(at)vision499.com wrote: 	
		  In a composite aircraft does the transponder antenna have to be outside the fuselage? 	


If your composite is fiberglass, it does not have to be on the outside.  If it's carbon fiber, then you may have some issues. 

 

 	  mike(at)vision499.com wrote: 	
		  

If it can be inside how do you make a ground plane? 	


I used aluminum. Here's how I built mine. 

http://www.velocity-xl.com/blog/2013/11/07/13-99-transponder-antenna-ground-plane/



 	  mike(at)vision499.com wrote: 	
		  Is it OK to be close to the COM antenna 	


In a perfect world, they would be as far apart as possible.  I'm sure there's a recommended minimum.  But I don't know what that is.

ceengland7(at)gmail.com
Guest

Posted: Sun Nov 12, 2017 5:32 pm Post subject: Transponder antenna

That design is great for those of us who are financially challenged; you 

can buy the little spike antenna for around $20. Add a bit of scrap 

aluminum & you're done.

On 11/12/2017 7:02 PM, donjohnston wrote:

 	  Quote: 	

 mike(at)vision499.com wrote:

> In a composite aircraft does the transponder antenna have to be outside the fuselage?

 If your composite is fiberglass, it does not have to be on the outside.  If it's carbon fiber, then you may have some issues.

 mike(at)vision499.com wrote:

> If it can be inside how do you make a ground plane?

 I used aluminum. Here's how I built mine.

 http://www.velocity-xl.com/blog/2013/11/07/13-99-transponder-antenna-ground-plane/

 mike(at)vision499.com wrote:

> Is it OK to be close to the COM antenna

 In a perfect world, they would be as far apart as possible.  I'm sure there's a recommended minimum.  But I don't know what that is.

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donjohnston

Joined: 13 Dec 2009
Posts: 231

Posted: Sun Nov 12, 2017 6:50 pm Post subject: Re: Transponder antenna

 	  ceengland7(at)gmail.com wrote: 	
		  That design is great for those of us who are financially challenged; you 

can buy the little spike antenna for around $20. Add a bit of scrap 

aluminum & you're done. 	




Not sure about the "financially challenged" comment. I didn't see the benefit to spending $100's on something that I could build for about $25. 



If that makes me "Financially challenged" then so be it.

ceengland7(at)gmail.com
Guest

Posted: Sun Nov 12, 2017 7:15 pm Post subject: Transponder antenna

An earlier post mentioned a dipole for ~$100.00. The $20+aluminum scrap 

is the alternative for us 'financially challenged'. When I wrote 'That 

design', I was referring to the spike.

On 11/12/2017 8:50 PM, donjohnston wrote:

 	  Quote: 	

 ceengland7(at)gmail.com wrote:

> That design is great for those of us who are financially challenged; you

> can buy the little spike antenna for around $20. Add a bit of scrap

> aluminum & you're done.

 Not sure about the "financially challenged" comment. I didn't see the benefit to spending $100's on something that I could build for about $25.

 If that makes me "Financially challenged" then so be it.

---

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Airdog77

Joined: 24 Nov 2013
Posts: 80
Location: Northern Virginia

Posted: Sun Nov 12, 2017 7:15 pm Post subject: Re: Transponder antenna

 	  Quote: 	
		  If your composite is fiberglass, it does not have to be on the outside. If it's carbon fiber, then you may have some issues. 	




Good point.  I should have noted the carbon fiber caveat.  



I went the same way you did initially Don, and it is fairly easy and cost effective.  But then after I ran across a few builders who used the L2, it solved my issue of finding a location for mounting the antenna, and also kept from having anything poking out (for us non-CF folks!).



Cheers,

Wade

_________________
Airdog
Wade Parton
Building Long-EZ N916WP
www.longezpush.com

steve(at)tomasara.com
Guest

Posted: Mon Nov 13, 2017 6:45 am Post subject: Transponder antenna

A word of caution related to putting your transponder antenna inside your cabin...



*IF* you are or will be using an ADS-B out 1090 MHz transponder on the antenna in question be aware that it's output is enough different than the non-ADS-B transponder that where the later would work with no problem, the former may inject "ticks" into your audio.

My antenna is an exterior antenna just under my legs with a minimum (1/4 wave radius) circular ground plane (it's been tested and provides and excellent match) and when I switched from a traditional transponder to a Garmin GTX-335 ticks were introduced into the audio.Â  I've got an otherwise very tight and well performing audio install with very careful consideration of grounds, returns etc.Â Â 

I've debugged enough to be *quite* certain that the interference path is from the energy radiated off of the antenna itself into the mic circuitry on my panel mount Sigtronics intercom.

If you google a bit, you will discover that there are many people who similarly had ticks introduced into their audio once they upgraded their 1090 MHz transponder to being ADS-B out capable.

Though I believeÂ  the real fix in my install will be to make my intercom less sensitive to RF Field pulses, I'm still not considering moving my transponder antenna inside as it would certainly make the problem worse...Â  I might consider it in the future once I mitigate the tick issue with it in its current location.

Steve Stearns

Longeze N45FC

Boulder/Longmont CO.

Airdog77

Joined: 24 Nov 2013
Posts: 80
Location: Northern Virginia

Posted: Mon Nov 13, 2017 9:04 am Post subject: Re: Transponder antenna

Steve,



Good to know! 



And clearly, this is a lesson for me to be more clear...   



 	  Quote: 	
		  A word of caution related to putting your transponder antenna inside your cabin... 	




Although I know you're talking about the "old style" antenna, I plan on mounting the L2 antenna at the outboard end of the strake at the junction with the wing.  Still quite a ways from the comm antenna in the vertical winglet, but also a decent ways out from the pilot/GIB and cabin electronics.



Cheers,

Wade

_________________
Airdog
Wade Parton
Building Long-EZ N916WP
www.longezpush.com

berkut13(at)berkut13.com
Guest

Posted: Fri Nov 24, 2017 8:10 am Post subject: Transponder antenna

So the noise is breaking intercom squelch?  

  

 Iâ€™ve noticed that in many EZ type installations, the transponder RF  â€œclickingâ€ noise is actually getting in to the headset itself.  Especially  if it is the active noise canceling variety.  It didnâ€™t seem to matter what  intercom was being used, VOX system shielding, ground separation and even  ferrite chokes added to the power/coax/audio lines...or even transponder.   In one case I could even unplug the headset and still get the noise.

  

 Mostly, I found that I can get the intensity of the noise to change (and  even disappear in some positions) as I rotate my head (with headset on) or move  to different parts of the cabin and/or moving the control box around.  It  can be replicated on the ground as well if you are in an active surveillance  area and can get your transponder to be active.  

  

 Try that and using a different brand and type of headset and see if you  have similar results.  If so, there is not much you can do about it but  change headset vendor/type if you find a quiet one or increase the size of the  ground plane if you have the room â€“ which is quite limited in an EZ.

  

 Let us know what you find.

  

 -James

 Berkut/Race 13

  

  

    

  From: Steve Stearns (steve(at)tomasara.com) 

 Sent: Monday, November 13, 2017 8:43 AM

 To: aeroelectric-list(at)matronics.com (aeroelectric-list(at)matronics.com)  

 Subject: Re: Re: Transponder  antenna

  



   *IF* you are or will be using an ADS-B out 1090 MHz transponder on the  antenna in question be aware that it's output is enough different than the  non-ADS-B transponder that where the later would work with no problem, the  former may inject "ticks" into your audio.

  

 I've debugged enough to be *quite* certain that the interference path is  from the energy radiated off of the antenna itself into the mic circuitry on my  panel mount Sigtronics intercom.

meyerkc135(at)gmail.com
Guest

Posted: Fri Nov 24, 2017 5:37 pm Post subject: Transponder Antenna

Bob, etc all.,Thank you.Â 

For the short term, I bought a piece of 1/8" brass rod, turned down and soldered the old connector to this rod, put the ball on the end and installed... Going to test fly tomorrow. Matched the length, etc...Â 

I will explore the internal options shortly. Slowly getting rid of drag. Need to do it faster though.Â 

Happy Flyin'!Â 

Andy

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