Wow .....ok
How about sharing the MSO system that your in.
What type of converter is it?
Who's the manufacturer of the converter.
Tell us everything about signal level, forward and reverse paths and we might be able to assist. Right now your question is too vague and general. It would be like asking "My car is making a noise: What is it?"
The more detail you share, the more we can pinpoint and get you going in the right direction.
We look forward to it.
RadioMan