I installed a Clarion FM200 into my W203 C-class with the Audio 10 HU.

It works fine when off, no static on the FM radio, yet when I turn it on it doesn't block all the radio frequencies and has a lot of static.

Are FM modulators this bad? Should I expect static?

I have checked the antenna adaptors and don't think they are to blame since the FM radio works fine. Also the RCAs are built into the device and I have tried several RCA-headphone adaptors. I suspect it might be a grounding issue since that's the only connection I have left to check, yet before I take apart everything again I was hoping someone might help diagnos my problem.

Thanks