Here's my summary on the topic...let me know where I am wrong....

In USA you can fly to 17,999' WITHOUT any transponder at all (class E
or G with some exceptions)

If you have a transponder rated only to 15,000", you must have the
transponder "on" and you can only fly to 15,000 (legally)

If you have the "high Power" transponder you can fly up to 17,999
legally

To fly a glider in class A you need "special permission" waiver etc or
whatever.

It is possible to get permission to above 18,000 without a transponder
at all. Wave camps, wave windows, etc.

It is probably more likely to get permission, with a transponder.

Why not just tell the nice man your transponder is only good to 15,000
when you ask permission to go into class A?

If you intend to fly above 15,000, why not just contact ATC and say
"I'm looking to fly above 15,000 but only have the low power
transponder?

If you fly above 15,000 regularly why not just buy the higher power
transponder in the first place?

If you have the old, low power transponder, I am sure it would be easy
to sell, or trade in for high power model!

We installed the trig TT21 in our club glider. One of our airline
pilot guys tried it out and contacted both NY approach, and
Philadelphia approach....both said the signal was very strong.
Probably with a proper install, and antenna the low watt transponder
may actually put out more power into the air than a poorly installed
high power transponder?? Also, we have an agreement to use 1201 code,
so they know it's a glider. Only trouble is, we seldom get that high
around here. State record is around 17,000......maybe somebody went
higher but never claimed..

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