Sega Naomi only outputs 240p via RGB to S-Video converter

[Four Wudude]

I'm using an Axunworks RGB-2YC RGB to S-Video converter, but I can only get it to output 240p. My goal is to get a 480i signal.I've done everything I can think of as far as dip switches go. It's either 15khz at 240p or 32lhz which shows up as a scrambled mess obviously.
Is there anything else I should try or am I just out of luck? Are there other converters out there that will do 480i?