This DVD has an FM transmitter, not a modulator.
An FM transmitter transmits the audio over the air to your car radio over a selectable channel. If that transmission interferes with a strong radio station over the same frequency, this will be a problem.
An FM modulator enables a direct connection to your stereo’s antenna, completely blocking reception and just providing the DVD input, for clear audio. It is typically controlled through an enable/disable switch.
Anyway, contrary to what it says in the description, and what it says on the box, it does NOT have a modulator (and buying one in Best Buy is $100).
The video quality on the screen is so-so.
Still an OK buy for the cost, but just be aware.