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Transponder antenna

 
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mike(at)vision499.com
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PostPosted: Sat Nov 11, 2017 4:15 pm    Post subject: Transponder antenna Reply with quote

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
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PostPosted: Sat Nov 11, 2017 5:17 pm    Post subject: Transponder antenna Reply with quote

Mike,

FWIW, I used the Archer transponder antenna for composite aircraft. It is a full wave antenna that doesn’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]


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Airdog77



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

PostPosted: Sun Nov 12, 2017 2:00 am    Post subject: Re: Transponder antenna Reply with quote

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


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donjohnston



Joined: 13 Dec 2009
Posts: 231

PostPosted: Sun Nov 12, 2017 5:02 pm    Post subject: Re: Transponder antenna Reply with 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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ceengland7(at)gmail.com
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PostPosted: Sun Nov 12, 2017 5:32 pm    Post subject: Transponder antenna Reply with quote

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

PostPosted: Sun Nov 12, 2017 6:50 pm    Post subject: Re: Transponder antenna Reply with 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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ceengland7(at)gmail.com
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PostPosted: Sun Nov 12, 2017 7:15 pm    Post subject: Transponder antenna Reply with quote

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

PostPosted: Sun Nov 12, 2017 7:15 pm    Post subject: Re: Transponder antenna Reply with quote

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


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steve(at)tomasara.com
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PostPosted: Mon Nov 13, 2017 6:45 am    Post subject: Transponder antenna Reply with quote

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.  I've got an otherwise very tight and well performing audio install with very careful consideration of grounds, returns etc.  
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 believe  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...  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.


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Airdog77



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

PostPosted: Mon Nov 13, 2017 9:04 am    Post subject: Re: Transponder antenna Reply with quote

Steve,

Good to know!

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

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


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berkut13(at)berkut13.com
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PostPosted: Fri Nov 24, 2017 8:10 am    Post subject: Transponder antenna Reply with quote

So the noise is breaking intercom squelch?

I’ve noticed that in many EZ type installations, the transponder RF “clicking” noise is actually getting in to the headset itself. Especially if it is the active noise canceling variety. It didn’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 – 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.


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meyerkc135(at)gmail.com
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PostPosted: Fri Nov 24, 2017 5:37 pm    Post subject: Transponder Antenna Reply with quote

Bob, etc all.,Thank you. 
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... 
I will explore the internal options shortly. Slowly getting rid of drag. Need to do it faster though. 
Happy Flyin'! 
Andy


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