05 Nav H2, Need to improve the FM modulator used for DVD player

[CMY4X4]

it uses an FM modulator for a DVD player that transmits an FM signal, it doesn't sound very good and we want to replace it with an INLINE modulator that goes between the car antenna and the radio. 2 Questions: What type of antennna input does the 05 Nav radio have and Who sells quality FM modulators? I had an Alpine one for years that worked great with a cd changer.

Thanks