On Sunday, June 9, 2019 at 5:43:42 AM UTC-7, wrote:
I got the impression that he wasn't that familiar with the Trig unit or gliders. So, what kind output should I be seeing 4' from the glider? What could be causing the low output? The battery was almost, if not completely, fully charged. Why would the frequencies drift?

Why are you asking r.a.s. these questions?... the test technician was right there testing your transponder. Ask him. Especially ask him exactly what he did to get it to pass.

I also would not be sitting on a transponder antenna. You are also a sack of water that may affect/obstruct some of the signal. I would get the antenna back in the tail boom. Away from metal structures. An external 1/4 wave antenna with ground plane may be better.

The RF output that should be seen is at least what is specified in the transponder RF test in 14 CFR Part 43 Appendix F. But it’s aiming at seeing 70W for a nominal 125W or 125W for a nominal 250W transponder. So what is you transponder a TT21 or TT22? But either way, the initial power measurements you mention are a clear fail.

Trig transponders rely on the use of low-loss cabling and proper antenna installation. The Trig install documentation is well written and very clear about what is needed. With any transponder cabling and antenna are suspect any time the power is too low. I would hope a technician connects direct to the coax or transponder RF output connector and checks that if in doubt.

Why do frequencies drift? Why do they not (well strictly they always are)? It’s all the magic power of crystals. Frequency reference crystals sometimes age badly, might not like the transponder being dropped or vibrated around in a trailer, or the electronics that drive the phase lock loop/frequency multipliers goes wonky... but I would not rely on one test with one technician with one test set. Have it rechecked by somebody else and/or just get it to Midcontibent for them to check out.