Yes.

I have a TT-22 and PowerFLARM portable and it works as you asked. I've
identified another glider by his contest call sign whereas he's only
been able to see my ICAO address since he's not yet downloaded the
latest flarmnet database.

On 1/7/2017 7:37 AM, wrote:
If someone has a Trig or other Mode S transponder which does NOT have an ADSB source connected to it, but the owner HAS entered the correct FAA issued ID, does the Trig broadcast that ID so that other PowerFlarm equipped gliders can exclude (in theory) the Mode C, PCAS alert from the PowerFlarm?

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Dan, 5J