Comment by jjwiseman

A transponder in a car is not an "aircraft station" (§ 87.5), therefore it is not covered by aircraft "license-by-rule" (§ 87.18(b)), so transmitting would be operating without a valid authorization (§ 1.903(a)). https://www.ecfr.gov/current/title-47/chapter-I/subchapter-D...