Locating Transponder Antenna on top of the fuselage instead of under it.

On Saturday, December 28, 2019 at 4:10:30 PM UTC-8, wrote:
"Pay attention to the proper ground plane installation with any of the standard external transponder 1/4 wave antenna. That is very important."
Can the ground Plane be inside a carbon fibre fuselage for an external blade type antenna ?
Dan

Yes,

http://www.craggyaero.com/antennas.htm



Richard
www.craggyaero.com

The ground plane in my glider is mounted to the inside of the carbon
skin and I'm told my transponder is quite visible.Â* My installation also
passed the ADS-B test with flying colors.

On 12/28/2019 5:10 PM, wrote:
"Pay attention to the proper ground plane installation with any of the standard external transponder 1/4 wave antenna. That is very important."
Can the ground Plane be inside a carbon fibre fuselage for an external blade type antenna ?
Dan

--
Dan, 5J

On Saturday, December 28, 2019 at 4:10:30 PM UTC-8, wrote:
"Pay attention to the proper ground plane installation with any of the standard external transponder 1/4 wave antenna. That is very important."
Can the ground Plane be inside a carbon fibre fuselage for an external blade type antenna ?
Dan

The ground plane you install would normally be inside the CF fuselage. And the antenna manufacture or glider manufacturer should provide instructions on how to do this properly. A part of the point of that aluminium plate or foil tape ground plane is to help with a good connection to the coax cable ground. In some cases you might scuff the inside of the fueslage to help make additional electrical connection to the carbon fibre weave. *Follow the directions your glider manufacturer provides.* A plate especially can also help provide a good solid surface for antenna lock washers to engage with. Clearly here the CF will act in part as a ground plane (even without a good direct electrical connection, but by backing it with a better conductor with good connection to the coax you are helping things along).

Well here is a link to a picture of a Ventus with the transponder antenna located as per Schempp Hirth.
Seems to work well only is straight flight. In any banking flight, the antenna is shadowed by the fuselage and/or wings.
Maybe a location on the turtledeck is better ?

https://www.airliners.net/photo/-/Sc...HgcaJ1/QJ2lC9A

Dan

On Saturday, December 28, 2019 at 9:23:02 PM UTC-8, wrote:
Well here is a link to a picture of a Ventus with the transponder antenna located as per Schempp Hirth.
Seems to work well only is straight flight. In any banking flight, the antenna is shadowed by the fuselage and/or wings.
Maybe a location on the turtledeck is better ?

https://www.airliners.net/photo/-/Sc...HgcaJ1/QJ2lC9A

Dan

Thanks for the photo, ouch yep that looks like a dopey position, if above is the only other practical option I'd do that.

I think while Darryl's suggestion will work quite well, it is more
effort than is required.Â* The BNC connector and the nut and washer of a
rod antenna will provide the necessary electrical connection to the
ground plane.Â* With a blade antenna, the mounting studs will make a good
mechanical connection.

In my former LAK-17a, I used an aluminum square cut to the dimensions
specified in the antenna installation sheet and rolled it over an oxygen
tank to match the internal curvature of the fuselage aft of the landing
gear.Â* I glued it in place with contact cement knowing that the studs
and BNC would make a good mechanical and electrical connection.Â* It
worked great!Â* I mounted the antenna offset to one side for two
reasons;Â* first, the joint line of the fuselage halves was thicker than
the length of the studs and BNC, and second, it insured that the blade
antenna would not catch on the ramp when loading and unloading the
fuselage in the trailer.

On 12/28/2019 7:43 PM, Darryl Ramm wrote:
On Saturday, December 28, 2019 at 4:10:30 PM UTC-8, wrote:
"Pay attention to the proper ground plane installation with any of the standard external transponder 1/4 wave antenna. That is very important."
Can the ground Plane be inside a carbon fibre fuselage for an external blade type antenna ?
Dan
The ground plane you install would normally be inside the CF fuselage. And the antenna manufacture or glider manufacturer should provide instructions on how to do this properly. A part of the point of that aluminium plate or foil tape ground plane is to help with a good connection to the coax cable ground. In some cases you might scuff the inside of the fueslage to help make additional electrical connection to the carbon fibre weave. *Follow the directions your glider manufacturer provides.* A plate especially can also help provide a good solid surface for antenna lock washers to engage with. Clearly here the CF will act in part as a ground plane (even without a good direct electrical connection, but by backing it with a better conductor with good connection to the coax you are helping things along).


--
Dan, 5J

On Saturday, December 28, 2019 at 6:43:02 PM UTC-8, Darryl Ramm wrote:
On Saturday, December 28, 2019 at 4:10:30 PM UTC-8, wrote:
"Pay attention to the proper ground plane installation with any of the standard external transponder 1/4 wave antenna. That is very important."
Can the ground Plane be inside a carbon fibre fuselage for an external blade type antenna ?
Dan

The ground plane you install would normally be inside the CF fuselage. And the antenna manufacture or glider manufacturer should provide instructions on how to do this properly. A part of the point of that aluminium plate or foil tape ground plane is to help with a good connection to the coax cable ground. In some cases you might scuff the inside of the fueslage to help make additional electrical connection to the carbon fibre weave. *Follow the directions your glider manufacturer provides.* A plate especially can also help provide a good solid surface for antenna lock washers to engage with.. Clearly here the CF will act in part as a ground plane (even without a good direct electrical connection, but by backing it with a better conductor with good connection to the coax you are helping things along).

Not all transponder antennas need a ground plane:

https://wingsandwheels.com/avionics-...as/l2-aae.html

On Sunday, December 29, 2019 at 6:48:52 PM UTC-8, 2G wrote:
On Saturday, December 28, 2019 at 6:43:02 PM UTC-8, Darryl Ramm wrote:
On Saturday, December 28, 2019 at 4:10:30 PM UTC-8, wrote:
"Pay attention to the proper ground plane installation with any of the standard external transponder 1/4 wave antenna. That is very important."
Can the ground Plane be inside a carbon fibre fuselage for an external blade type antenna ?
Dan

The ground plane you install would normally be inside the CF fuselage. And the antenna manufacture or glider manufacturer should provide instructions on how to do this properly. A part of the point of that aluminium plate or foil tape ground plane is to help with a good connection to the coax cable ground. In some cases you might scuff the inside of the fueslage to help make additional electrical connection to the carbon fibre weave. *Follow the directions your glider manufacturer provides.* A plate especially can also help provide a good solid surface for antenna lock washers to engage with. Clearly here the CF will act in part as a ground plane (even without a good direct electrical connection, but by backing it with a better conductor with good connection to the coax you are helping things along).

Not all transponder antennas need a ground plane:

https://wingsandwheels.com/avionics-...as/l2-aae.html

You are replying to a thread that clearly stated "with any of the standard external transponder 1/4 wave antenna." Are you adding value here?

On Friday, December 27, 2019 at 2:34:32 PM UTC-5, wrote:
Hi all,
Planning to install a Transponder Antenna on my Ventus CM.
Schempp Hirth indicates the possibilty of installing on top of the fuselage , behind the engine compartment doors.
Regarding being seen by ATC and Airlines, would that location perform better/worse/same as the standard location on side of fuselage - above gear doors ?
Dan

After reading lots of comments I am still wondering why not just mount on the bottom of the fuselage in the conventional manner?
UH

UH, as I said in my earlier post it was way easier to install on the turtle deck than down by the gear. In my 27, it took less than 4 hours from start to finish including the transponder and power routing. The longest portion was the routing of the antenna cable up through the tunnel to the panel, not alot of room in there I didnt crimp on the bnc to that end until after I fished it up to the panel. I mounted the blade as far back as I could possibly reach in the fuselage which is close to the junction of the flap and wing.

CH