ContestID67 wrote:

#4 - Transponders - As this device transmitts more often than you are
likely to do with your transceiver (and maybe continuously in high
traffic areas), this will be a significant power drain.

For the typical Microair or Becker installation, the best choices for
gliders in the US, it's about 400 ma at idle. That rises to about 500 ma
in areas of VERY heavy radar coverage, and another 100 ma in the winter
to heat the encoder. The peak current demand is much smaller than a
communication radio, but it's higher on average.

Because I live
near a mode-C vail, I might have to add altitude encoding on top of
that. Therefore I hope that we don't have to have them. Have there
been accidents that would have been prevented if the glider had had a
transponder?

No disasters like an airliner hitting a glider (at least in the US), but
several collisions with general aviation aircraft and at least one
fighter aircraft might have been avoided if the glider had used a
transponder and the airplane pilot was in contact with ATC (IFR flight
plan or using Flight Following). Or, if either one was using a
transponder detector, the collisions might have been avoided.

"A lot" of glider pilots in high traffic areas like Minden/Reno,
Southern California, and elsewhere have installed transponders, so one
could easily imagine some collisions have been avoided by doing so. It
would be very hard to estimate how many.
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Eric Greenwell
Washington State
USA