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ASW27 Trasponder Antenna Installation Inside Fuselage.



 
 
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  #21  
Old March 6th 16, 05:42 AM posted to rec.aviation.soaring
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Default ASW27 Trasponder Antenna Installation Inside Fuselage.

Another option is to install the antenna on top of the fuselage just behind where the cockpit vent exhaust would be. I think it was Andy Durbin that posted many years ago that he did some research which involved talking to people actually involved in building ATC radars, and the consensus was that the top of the fuselage is just as good as the bottom.

Install a pretty blade antenna on top and paint some cool lightning bolts on it, just put a sticker like this on it:
http://static.seton.ca/media/catalog...s-s2283-ba.jpg

On Saturday, March 5, 2016 at 1:21:09 PM UTC-8, Darryl Ramm wrote:
I'm not sure why all the complex approach of vertical fin mounted transponder and FLARM antennas is needed in the first place. The transponder antenna behind the gear door works fantastically well, is really not a hassle unless you are stupidly careless.. and then it's easy to replace anyhow). People are getting good performance of FLARM antennas mounted in the cockpit area, including the nose cone area of ASW-27.

  #22  
Old December 30th 17, 11:58 PM posted to rec.aviation.soaring
OHM Ω http://aviation.derosaweb.net
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Default ASW27 Trasponder Antenna Installation Inside Fuselage.

I am resurrecting this old post as some pilots I know are installing transponders this winter. The key questions are the location of the antenna and the type to use.

1) Does the blade type antenna provide "better" coverage than the rod type? What about aerodynamics between the two?

2) Potentially dumb question - Ground Planes - It was mentioned above by UH that the ground plane should be on the outside of a CF glider. As carbon blocks RF transmission is it considered conductive? If conductive, and grounded to the avionics, can the CF constitute a ground plane? I saw another RAS thread on this same subject without a clear consensus given.

Thanks, John
  #23  
Old December 31st 17, 02:01 AM posted to rec.aviation.soaring
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Default ASW27 Trasponder Antenna Installation Inside Fuselage.


1) Does the blade type antenna provide "better" coverage than the rod type? What about aerodynamics between the two?


I happen to have checked the pattern at 1M over the transponder band on a rami blade versus a simple 1/4 wave. They both seemed pretty close in gain and (non)directionality.



2) Potentially dumb question - Ground Planes -

Actually an really interesting question.

An outside ground plane should be ideal from an RF standpoint, but how would you do it from a low drag standpoint, and is it worth it?

I don't have CF there, but would still want to put the ground plane inside and hope it was good enough. Officially, it seems like it ought to be up to the av tech signing off on the install, but finding one that has a clear understanding of this seems unlikely. I guess you could try to measure the installed antenna pattern, but even if you did, what is good enough? Maybe a VSWR spec on the transponder, but CF seems likely to make loss which would make that ok. It comes down to antenna system loss. For the places you plan to fly, is it good enough so the transponder does it's job of keeping you safe. I would do what is easy, (inside ground plane) and then try it out and see if it works. Not sure if the FAA's ADSB report includes signal strength information. It ought to.

  #24  
Old December 31st 17, 02:23 AM posted to rec.aviation.soaring
Dan Marotta
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Default ASW27 Trasponder Antenna Installation Inside Fuselage.

I installed a blade type antenna on the belly of my LAL-17a several
years ago and installed an aluminum ground plane cut to the
specifications in the Trig-22 Installation Manual.Â* I installed the
ground plane inside the fuselage and the system always showed over 175
watts during transponder tests.Â* It may have been higher power, but I
know it was at least that.

On 12/30/2017 6:01 PM, wrote:
1) Does the blade type antenna provide "better" coverage than the rod type? What about aerodynamics between the two?

I happen to have checked the pattern at 1M over the transponder band on a rami blade versus a simple 1/4 wave. They both seemed pretty close in gain and (non)directionality.


2) Potentially dumb question - Ground Planes -

Actually an really interesting question.

An outside ground plane should be ideal from an RF standpoint, but how would you do it from a low drag standpoint, and is it worth it?

I don't have CF there, but would still want to put the ground plane inside and hope it was good enough. Officially, it seems like it ought to be up to the av tech signing off on the install, but finding one that has a clear understanding of this seems unlikely. I guess you could try to measure the installed antenna pattern, but even if you did, what is good enough? Maybe a VSWR spec on the transponder, but CF seems likely to make loss which would make that ok. It comes down to antenna system loss. For the places you plan to fly, is it good enough so the transponder does it's job of keeping you safe. I would do what is easy, (inside ground plane) and then try it out and see if it works. Not sure if the FAA's ADSB report includes signal strength information. It ought to.


--
Dan, 5J
  #25  
Old December 31st 17, 05:22 AM posted to rec.aviation.soaring
Darryl Ramm
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Default ASW27 Trasponder Antenna Installation Inside Fuselage.

On Saturday, December 30, 2017 at 2:58:29 PM UTC-8, OHM Ω http://aviation.derosaweb.net wrote:
I am resurrecting this old post as some pilots I know are installing transponders this winter. The key questions are the location of the antenna and the type to use.

1) Does the blade type antenna provide "better" coverage than the rod type? What about aerodynamics between the two?


The blade antenna is a rod antenna encased in plastic, they all have the same RF performance.

2) Potentially dumb question - Ground Planes - It was mentioned above by UH that the ground plane should be on the outside of a CF glider. As carbon blocks RF transmission is it considered conductive? If conductive, and grounded to the avionics, can the CF constitute a ground plane? I saw another RAS thread on this same subject without a clear consensus given.


Follow the directions of your glider manufacture. A proper aluminum grounding plane behind the carbon fiber will provide a better ground than relying on the carbon fiber alone, and manufacturers will be recommending to do that. "Considered conductive" and actually how good a connection to the ground you can make and the impedance of/to that ground at 1GHz you don't know....

Stop trying to overthink stuff, just crack open a manufacture's TN (or one close) and follow the instructions. In the case of an A&P IA signing off on any work I would hope they expect that to have been done.

Installations of antennas requiring ground planes in a carbon fuselage without a separate ground plane is counter to guidance provided in AC No: 43.13-2B. Your A&P, or anybody else working on an aircraft, should be aware of this.



  #26  
Old December 31st 17, 02:33 PM posted to rec.aviation.soaring
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Default ASW27 Trasponder Antenna Installation Inside Fuselage.


AC 43.13B 308d says you need a backing ground plane.
But I didn't see any special details for CF versus other composites?

Following the instructions from the glider manufacturer seems smart.

  #27  
Old December 31st 17, 07:03 PM posted to rec.aviation.soaring
Scott Williams
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Default ASW27 Trasponder Antenna Installation Inside Fuselage.

On Sunday, December 31, 2017 at 7:33:39 AM UTC-6, wrote:
AC 43.13B 308d says you need a backing ground plane.
But I didn't see any special details for CF versus other composites?

Following the instructions from the glider manufacturer seems smart.


My std Cirrus has a schempp-Hirth TN that clearly spells out the installation
of the blade antenna. but it allows either aluminum or copper for a ground plane.
I chose a copper plate 0f .043 thick.
Trigg 22 has good output, but the 'sensitivity' was right on the low tolerance.
Any thoughts or insights?
thanks,
Scott
  #28  
Old December 31st 17, 07:13 PM posted to rec.aviation.soaring
Darryl Ramm
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Default ASW27 Trasponder Antenna Installation Inside Fuselage.

On Sunday, December 31, 2017 at 5:33:39 AM UTC-8, wrote:
AC 43.13B 308d says you need a backing ground plane.
But I didn't see any special details for CF versus other composites?


The big note in plain English and bolt text staring you in the face in AC 43.13-2B: "NOTE: Carbon Fiber composite material, while conductive has not been found to be adequate as a ground plane."
  #29  
Old December 31st 17, 07:58 PM posted to rec.aviation.soaring
Darryl Ramm
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Default ASW27 Trasponder Antenna Installation Inside Fuselage.

On Sunday, December 31, 2017 at 10:03:37 AM UTC-8, Scott Williams wrote:
On Sunday, December 31, 2017 at 7:33:39 AM UTC-6, wrote:
AC 43.13B 308d says you need a backing ground plane.
But I didn't see any special details for CF versus other composites?

Following the instructions from the glider manufacturer seems smart.


My std Cirrus has a schempp-Hirth TN that clearly spells out the installation
of the blade antenna. but it allows either aluminum or copper for a ground plane.
I chose a copper plate 0f .043 thick.
Trigg 22 has good output, but the 'sensitivity' was right on the low tolerance.
Any thoughts or insights?
thanks,
Scott


What did the technician doing the test recommend? If there was a doubt why did they not direct connect test the transponder?

These measurements are not highly precise. If its within tolerance then go fly. If not then get a different avionics technician to repeat the test if possible and if its bad then direct connect test the transponder to see it is likely the transponder or cable/antenna..
  #30  
Old December 31st 17, 08:25 PM posted to rec.aviation.soaring
Scott Williams
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Posts: 198
Default ASW27 Trasponder Antenna Installation Inside Fuselage.

On Sunday, December 31, 2017 at 12:58:25 PM UTC-6, Darryl Ramm wrote:
On Sunday, December 31, 2017 at 10:03:37 AM UTC-8, Scott Williams wrote:
On Sunday, December 31, 2017 at 7:33:39 AM UTC-6, wrote:
AC 43.13B 308d says you need a backing ground plane.
But I didn't see any special details for CF versus other composites?

Following the instructions from the glider manufacturer seems smart.


My std Cirrus has a schempp-Hirth TN that clearly spells out the installation
of the blade antenna. but it allows either aluminum or copper for a ground plane.
I chose a copper plate 0f .043 thick.
Trigg 22 has good output, but the 'sensitivity' was right on the low tolerance.
Any thoughts or insights?
thanks,
Scott


What did the technician doing the test recommend? If there was a doubt why did they not direct connect test the transponder?

These measurements are not highly precise. If its within tolerance then go fly. If not then get a different avionics technician to repeat the test if possible and if its bad then direct connect test the transponder to see it is likely the transponder or cable/antenna..


in short,
New trig tt22, new only 14 inch antenna coax, new antenna, copper ground plane, trig authorized shop doing test, fresh battery with good voltage.
Tech reports using two different 'test rigs' , also report "sensitivity is on the low tolerance, but I'll pass it" with no other suggestions.
I followed up with Trig factory tech line, maybe have to send it in for a factory check. Factory rep had on suggestions.
I have no idea just what 'sensitivity is. factory was helpful, but I think maybe "sensitivity" may be outside of the influence of installation variables.
I was hoping for someone to have an insight.

Thanks,
Scott
 




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