For team flying, a number of US pilots have used Garmin RINO. Back
when they allowed position data to only be transmitted on the lower
power FRS band, air-to-air range was about 10 Nm. Then a few years
back, the FCC allowed use on the GMRS channels and airborne range
increased to 20 - 23 miles *if* the RINO is mounted so it's antenna is
above the canopy rail.

Yeah, it's one more gadget to add, but it's easy to use displays the
other glider/s bearing, distance, and altitude. It also allows a spot
(thermal) to be marked and that info transmitted to team members.
Polling may be individually enabled too, and that allows you to
request and receive position info from other "team" gliders without
their having to push their send button.

bumper
MKIV and QV
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