[krisoft]

> GPS transponders

I assume you mean ADS-B in? Is the receiver in the drone itself or in the ground station/transmitter?

[jaywalk]

Drones (generally) don't use ADS-B in or out.

[krisoft]

Okay, then what is a “GPS transponder”?

[jaywalk]

I'm guessing the comment was referring to the drone having a GPS receiver and relaying it's position to the base station.