Transponder Antenna Placement Fuselage Bottom - Minimize Damage?Exact Location

Planning on install of a Trig T22 on my Discus 2A. I see that SH recommends installation on bottom of fuselage near gear door canted off at an angle:

http://www.schempp-hirth.com/fileadm...0-4-D-2070.pdf

Any recommendations from experience on exactly where to place a stub antenna in such a way to minimize damage while moving into and out of trailer? Also, comments on pluses minuses of adding a ground plane?

Walter Rogers - WX

http://www.advancedaircraft.com/

The L2....

If your glider has fiberglass tail boon (no carbon fiber) this is a great solution....

We installed about 10 or 12 of these in gliders with no problems at all...


Cookie





On Saturday, January 17, 2015 at 7:50:16 PM UTC-5, WaltWX wrote:
Planning on install of a Trig T22 on my Discus 2A. I see that SH recommends installation on bottom of fuselage near gear door canted off at an angle:

http://www.schempp-hirth.com/fileadm...0-4-D-2070.pdf

Any recommendations from experience on exactly where to place a stub antenna in such a way to minimize damage while moving into and out of trailer? Also, comments on pluses minuses of adding a ground plane?

Walter Rogers - WX

I installed a flexible transponder antenna in the exact location specified by Schemmp-Hirth in a Discus B. If you were to hit it during loading, unloading or outlanding it just bends out the way. XPDR performance has been great to date though I'm yet to test it at maximum range. Though in gliding, maximum range is really not necessary. I did have to trim the mesh ground plane to fit due to control rods and fibreglass brackets in the area but again, no degradation of performance evident.

http://www.lxavionics.co.uk/transflex-mesh-antenna.htm

Case

On Saturday, January 17, 2015 at 8:03:13 PM UTC-5, Cookie wrote:
http://www.advancedaircraft.com/

The L2....

If your glider has fiberglass tail boon (no carbon fiber) this
is a great solution....

We installed about 10 or 12 of these in gliders with no problems at all...

Cookie

If you install an L2, MAKE SURE IT IS INSTALLED VERTICALLY !
"Works Great!" said the mechanic who glassed in some of these
horizontally. Don't do that!

If externally fitted, go for flexible. Fixed ones break and bend very
easily during operations. We did on our Discus b.

I'm sure everyone knows this already, but its worthwhile saying again: transponder antennas need to go on the bottom of the aircraft so they can have line-of-sight to the radar facility, without being in the shadow of the fuselage or the wings.

I mounted a blade antenna for my TT22 on the bottom of my LAK-17a as
follows:

Sufficiently aft of the gear door to allow a good margin (a couple of
inches) between the aft edge of the gear well and the forward mounting
screw of the antenna.

Sufficiently off center (right side in my case) because the fuselage
bonding joint is too thick for the length of the mounting screws.

Ground plane as described in the Trig installation manual. Transponder
check at the local avionics shop showed somewhere around 275 watts peak
power radiated by the antenna (IIRC).

As to damaging the antenna during trailering, I don't have a problem
with my LAK glider and trailer. The fuselage cradle holds the glider
high enough to prevent banging the antenna on the ramp. On landout I
suppose it's possible to come close enough to an obstruction to miss the
gear but hit the antenna, but I think the likelihood is pretty slim.

Here's a picture of my antenna as installed:
https://www.dropbox.com/s/bl0263bjml...tenna.jpg?dl=0

And here's the installation drawing for that antenna:
https://www.dropbox.com/s/msfnn6x10h...ak17a.jpg?dl=0

Good luck!

Dan

On 1/17/2015 5:50 PM, WaltWX wrote:
Planning on install of a Trig T22 on my Discus 2A. I see that SH recommends installation on bottom of fuselage near gear door canted off at an angle:

http://www.schempp-hirth.com/fileadm...0-4-D-2070.pdf

Any recommendations from experience on exactly where to place a stub antenna in such a way to minimize damage while moving into and out of trailer? Also, comments on pluses minuses of adding a ground plane?

Walter Rogers - WX

--
Dan Marotta

Well, yes on a METAL aircraft...and maybe carbon fiber...but fiberglass...no...the L2 antenna usually goes on the inside wall of the tail boom....radio waves go through fiberglass...


Cookie


On Sunday, January 18, 2015 at 9:40:48 AM UTC-5, Bob Pasker wrote:
I'm sure everyone knows this already, but its worthwhile saying again: transponder antennas need to go on the bottom of the aircraft so they can have line-of-sight to the radar facility, without being in the shadow of the fuselage or the wings.

But most 'modern' composite gliders have carbon in the fuselage, so act
like metal for RF purposes.

As far as sailplane antennas go, the AV-22 'lollipop stick' is far too
fragile; blade antenna looks prettier but the flex is probably optimal; I
back up the conductive fuselage with a mesh screen inside the skin as 'belt
and braces'.

At 18:25 18 January 2015, Cookie wrote:
Well, yes on a METAL aircraft...and maybe carbon fiber...but
fiberglass...no...the L2 antenna usually goes on the inside wall of the
tail boom....radio waves go through fiberglass...


Cookie


On Sunday, January 18, 2015 at 9:40:48 AM UTC-5, Bob Pasker wrote:
I'm sure everyone knows this already, but its worthwhile saying again:
transponder antennas need to go on the bottom of the aircraft so they can
have line-of-sight to the radar facility, without being in the shadow of
the fuselage or the wings.

On Sunday, January 18, 2015 at 12:15:22 PM UTC-7, pete purdie wrote:
But most 'modern' composite gliders have carbon in the fuselage, so act
like metal for RF purposes.

As far as sailplane antennas go, the AV-22 'lollipop stick' is far too
fragile; blade antenna looks prettier but the flex is probably optimal; I
back up the conductive fuselage with a mesh screen inside the skin as 'belt
and braces'.

At 18:25 18 January 2015, Cookie wrote:
Well, yes on a METAL aircraft...and maybe carbon fiber...but
fiberglass...no...the L2 antenna usually goes on the inside wall of the
tail boom....radio waves go through fiberglass...


Cookie


On Sunday, January 18, 2015 at 9:40:48 AM UTC-5, Bob Pasker wrote:
I'm sure everyone knows this already, but its worthwhile saying again:
transponder antennas need to go on the bottom of the aircraft so they can
have line-of-sight to the radar facility, without being in the shadow of
the fuselage or the wings.



I installed a blade antenna with groundplane (yes, you need one!) in the lower fuselage (where the factory said) on my Discus 2b and it has worked well for ten years and never been knocked off by ground handling.

If you decide to put it in the tail, make sure you have low-loss coaxial cable.

Mike