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Transponder Antenna Location

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jkreidler

Joined: 13 Feb 2008
Posts: 151
Location: Sheboygan Falls WI

Posted: Sat May 15, 2010 3:36 pm Post subject: Transponder Antenna Location

We have been told on more than one occasion that ATC was not seeing our transponder.  We have a Garmin GTX327 installed.  We are wondering if our antenna location might be the problem, our antenna is located in the center of the airplane just behind the firewall.  At the time we installed the antenna it looked like a good spot, but that was before we had the exhaust installed.  Not sure if the location is the problem or not, just wondering of anyone else has experienced any problems with the antenna in this location.  Thoughts appreciated.

_________________
Jason Kreidler
4 Partner Build - Sheboygan Falls, WI
Tony Kolar, Kyle Hokel, Wayne Elser, Jason Kreidler
N44YH - Flying - #40617

N777TY

Joined: 09 Apr 2006
Posts: 69
Location: Charlotte, NC

Posted: Sat May 15, 2010 3:51 pm Post subject: Re: Transponder Antenna Location

I doubt that's the problem..  Mine's on the right side.. maybe 10 inches to the right of the centerline (so it's not in the exhaust path)... and it works perfect.. never skipped a beat.. 



Have you had your txp checked per 91.413?  Did it pass that inspection?

_________________
RV-7A
N777TY

jkreidler

Joined: 13 Feb 2008
Posts: 151
Location: Sheboygan Falls WI

Posted: Sat May 15, 2010 4:10 pm Post subject: Re: Transponder Antenna Location

Yes, we had it inspected.



Our antenna is between the exhaust stacks and the exhaust exits behind the antenna.

_________________
Jason Kreidler
4 Partner Build - Sheboygan Falls, WI
Tony Kolar, Kyle Hokel, Wayne Elser, Jason Kreidler
N44YH - Flying - #40617

Dick Sipp

Joined: 11 Jan 2006
Posts: 215
Location: Hope, MI

Posted: Sat May 15, 2010 5:01 pm Post subject: Transponder Antenna Location

I occasionally get the same complaint.  I would say on about 5-10% of the 

controller changes.  It seems to occur more often when headed directly at 

the antenna sight and long or short range only rather than medium.  It 

almost always returns for the controller as the position relative to the 

sight changes.  The antenna is on the belly centerline about 14 inches aft 

of the firewall.



Dick Sipp

N110DV



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

From: "jkreidler" <jason.kreidler(at)regalbeloit.com>

Sent: Saturday, May 15, 2010 7:37 PM

To: <rv10-list(at)matronics.com>

Subject: Transponder Antenna Location



 	  Quote: 	
		   

 <jason.kreidler(at)regalbeloit.com>



 We have been told on more than one occasion that ATC was not seeing our 

 transponder.  We have a Garmin GTX327 installed.  We are wondering if our 

 antenna location might be the problem, our antenna is located in the 

 center of the airplane just behind the firewall.  At the time we installed 

 the antenna it looked like a good spot, but that was before we had the 

 exhaust installed.  Not sure if the location is the problem or not, just 

 wondering of anyone else has experienced any problems with the antenna in 

 this location.  Thoughts appreciated.



 --------

 Jason Kreidler

 4 Partner Build - Sheboygan Falls, WI

 Tony Kolar, Kyle Hokel, Wayne Elser, Jason Kreidler

 N44YH - Flying - #40617





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p=297856#297856

Kelly McMullen

Joined: 16 Apr 2008
Posts: 1188
Location: Sun Lakes AZ

Posted: Sat May 15, 2010 5:02 pm Post subject: Transponder Antenna Location

It is possible the exhaust stacks are shielding the antenna in that

case. Shouldn't be to hard to patch that hole and move antenna a foot

or so to right or left of exhaust.



On Sat, May 15, 2010 at 5:10 PM, jkreidler

<jason.kreidler(at)regalbeloit.com> wrote:

 	  Quote: 	
		   



 Yes, we had it inspected.



 Our antenna is between the exhaust stacks and the exhaust exits behind the antenna.



 --------

 Jason Kreidler

 4 Partner Build - Sheboygan Falls, WI

 Tony Kolar, Kyle Hokel, Wayne Elser, Jason Kreidler

 N44YH - Flying - #40617





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p=297859#297859

_________________
Kelly McMullen
A&P/IA, EAA Tech Counselor
KCHD

Kelly McMullen

Joined: 16 Apr 2008
Posts: 1188
Location: Sun Lakes AZ

Posted: Sat May 15, 2010 5:07 pm Post subject: Transponder Antenna Location

I'd be checking the antenna cable before I worried about the antenna

location. It isn't unusual to find a loose antenna cable in those

situations. If nothing obvious, ask avionics shop to do a field check

of the transponder, where they observe the output with a small

handheld receiver that will indicate output power. You should have had

a check like that very early in your flight test phase.



On Sat, May 15, 2010 at 4:37 PM, jkreidler

<jason.kreidler(at)regalbeloit.com> wrote:

 	  Quote: 	
		   



 We have been told on more than one occasion that ATC was not seeing our transponder.  We have a Garmin GTX327 installed.  We are wondering if our antenna location might be the problem, our antenna is located in the center of the airplane just behind the firewall.  At the time we installed the antenna it looked like a good spot, but that was before we had the exhaust installed.  Not sure if the location is the problem or not, just wondering of anyone else has experienced any problems with the antenna in this location.  Thoughts appreciated.



 --------

 Jason Kreidler

 4 Partner Build - Sheboygan Falls, WI

 Tony Kolar, Kyle Hokel, Wayne Elser, Jason Kreidler

 N44YH - Flying - #40617





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p=297856#297856

_________________
Kelly McMullen
A&P/IA, EAA Tech Counselor
KCHD

coop85(at)verizon.net
Guest

Posted: Sat May 15, 2010 5:32 pm Post subject: Transponder Antenna Location

Mine is in the same location, about a foot aft of the firewall, with the

same xpdr.  No issues to date with 450 hours.



Marcus



Do not archive



--

coop85(at)verizon.net
Guest

Posted: Sat May 15, 2010 5:32 pm Post subject: Transponder Antenna Location

Just speculating, but I wonder with your antenna that far forward if you are

getting some issues from the exhaust pipes?  As I mentioned previously mine

is a bit further back and while it does get a little dirty, it works great.



Marcus



Do not archive



--

jesse(at)saintaviation.co
Guest

Posted: Sat May 15, 2010 5:33 pm Post subject: Transponder Antenna Location

I've never seen a problem with the antenna right where you have it.  I'd also check the coax running to the antenna.  How high do you normally fly?



The only problem I've noticed is in a specific area about 50 miles east of our home airport here, so it could have something to do with the radar coverage.  I assume you've already verified that it isn't always in the same geographic area.



do not archive



Jesse Saint

Saint Aviation, Inc.

jesse(at)saintaviation.com

Cell: 352-427-0285

Fax: 815-377-3694



On May 15, 2010, at 7:37 PM, jkreidler wrote:



 	  Quote: 	
		   

 

 We have been told on more than one occasion that ATC was not seeing our transponder.  We have a Garmin GTX327 installed.  We are wondering if our antenna location might be the problem, our antenna is located in the center of the airplane just behind the firewall.  At the time we installed the antenna it looked like a good spot, but that was before we had the exhaust installed.  Not sure if the location is the problem or not, just wondering of anyone else has experienced any problems with the antenna in this location.  Thoughts appreciated.

 

 --------

 Jason Kreidler

 4 Partner Build - Sheboygan Falls, WI

 Tony Kolar, Kyle Hokel, Wayne Elser, Jason Kreidler

 N44YH - Flying - #40617

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=297856#297856

jkreidler

Joined: 13 Feb 2008
Posts: 151
Location: Sheboygan Falls WI

Posted: Sat May 15, 2010 5:52 pm Post subject: Re: Transponder Antenna Location

Kelly, we did have the typical inspection performed where he sets up a tests apparatus, but that is done in the shop.  Is there another way they test?



We have not narrowed it to a specific geographic location, it seems to happen at random.  Our suspicion is that the antenna is being shadowed by the exhaust pipes.  We were going to move the antenna back a foot or so, but wanted to get some feedback before making an assumption that that is the real problem.  If others have it in the same location and are not having the problem then we would need to dig deeper.  We did verify the cables and connections were good.

_________________
Jason Kreidler
4 Partner Build - Sheboygan Falls, WI
Tony Kolar, Kyle Hokel, Wayne Elser, Jason Kreidler
N44YH - Flying - #40617

Kelly McMullen

Joined: 16 Apr 2008
Posts: 1188
Location: Sun Lakes AZ

Posted: Sat May 15, 2010 6:18 pm Post subject: Transponder Antenna Location

Yes, there is a hand held ramp checker. They are supposed to test the

full system, which means receiving the signal from the antenna, not

connected to a load on the bench.



On Sat, May 15, 2010 at 6:52 PM, jkreidler

<jason.kreidler(at)regalbeloit.com> wrote:

 	  Quote: 	
		   



 Kelly, we did have the typical inspection performed where he sets up a tests apparatus, but that is done in the shop.  Is there another way they test?



 We have not narrowed it to a specific geographic location, it seems to happen at random.  Our suspicion is that the antenna is being shadowed by the exhaust pipes.  We were going to move the antenna back a foot or so, but wanted to get some feedback before making an assumption that that is the real problem.  If others have it in the same location and are not having the problem then we would need to dig deeper.  We did verify the cables and connections were good.



 --------

 Jason Kreidler

 4 Partner Build - Sheboygan Falls, WI

 Tony Kolar, Kyle Hokel, Wayne Elser, Jason Kreidler

 N44YH - Flying - #40617





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p=297869#297869

_________________
Kelly McMullen
A&P/IA, EAA Tech Counselor
KCHD

jkreidler

Joined: 13 Feb 2008
Posts: 151
Location: Sheboygan Falls WI

Posted: Sat May 15, 2010 6:34 pm Post subject: Re: Transponder Antenna Location

They did test the transponder in the airplane with a receiving unit set up away from the airplane in the hangar.  Not a bench test...



Do Not Archive

_________________
Jason Kreidler
4 Partner Build - Sheboygan Falls, WI
Tony Kolar, Kyle Hokel, Wayne Elser, Jason Kreidler
N44YH - Flying - #40617

speckter(at)comcast.net
Guest

Posted: Sun May 16, 2010 5:09 am Post subject: Transponder Antenna Location

I have mine on the centerline just aft of the fire wall.  Mine too looks

like the exhaust might block some of the signal, but it has worked fine all

the time.  Mine is quite far forward before the pipes get very far down

along the sides of the antenna.  I have the big Forsling exhaust that is

about 3" in diameter at the end.  



Gary Specketer



--

jcumins(at)jcis.net
Guest

Posted: Mon May 17, 2010 6:57 am Post subject: Transponder Antenna Location

Being a RF guy that does a lot of radio work for my company.  I would not

place any antenna between the Exhaust stacks you are blocking the radiation

of the antenna a lot.  Metal will reflect the radiation of the transmit.

Move the antenna to the far Right or Left and I bet it will work much

better.



John G. Cumins

President

 



2499 B1 Martin Rd

Fairfield Ca 94534

707-425-7100

707-425-7576 Fax

 

Your Total Technology Solution Provider



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