RD104E issues....

You have an antenna and coax problem, start with you are missing proper RF grounds which can create what is called Common Mode Current.

Go hear and read about Bonding and Common Mode Current.

 

These Road devil microphones are a very sensitive mic from what I understand. It's a condenser power mic, plus a noise cancelling mic all in one. You have to keep the gain turned down. It doesn't sound to me like the microphone is your problem, because in another thread you said this..

"Current road devil power mic is just about the worst. When I bought it, thought the squeal & "talkback" over a non-tb radio was just the cheap radio but it turns out that mic blows out something on the board no matter what you use it on."

What board are you talking about, the radio? What radio are you using this mic on? You say it works fine on a cheap cobra radio, so that's why I don't think the mic is your problem. Unless I'm reading your posts wrong.