Transponder: Mode-C or Mode-S?

On Tuesday, April 16, 2019 at 8:01:31 PM UTC-7, wrote:
On Sunday, September 11, 2011 at 11:54:26 PM UTC-4, Morteza Ansari wrote:
I recently bought a new bird and need to put a transponder in it. The
choice was obvious (until I took a closer look). Trig TT21 seems like
a great choice: small footprint, built-in encoder, 1090ES ADS-B out,
and descent price. However a bit more looking revealed more questions
than answers. It seems it requires an ISO GPS and one could not use
typical GPS sources we have in gliders, it is not clear if the ADS-B
out work with PowerFLARM (at least from what I have heard), and the
biannual testing cost 2-3x as much as mode-C.

Any thoughts/suggestions from more knowledgable folks?


Cheers,
Morteza

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Not sure how you got your conclusions or that gobbledygook you just uttered.
I have been using the TT-21 for over 10 years and it is flawless. It and the TT-22 are identical except for the transmit power. I have no GPS hooked to it or anything else. It runs like a normal txpndr. I hooked it up in one afternoon, and as mentioned has been working perfectly.

Welcome to r.a.s. This is an *excellent* first post.