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..