Mot. handsfree + noise in rig

If anyone wants to give me a hand with this I would appreciate it. I am having a brain fart day here and just can't figure this one out. We have us a Western Star rig and have added a Motorola handsfree kit to it with the 731 phone. All is well until we plug in the external antenna and we get noise from hell. (typical rmp based noise but only when the cell phone is activated and in use or by puching buttons and therefor using the handsfree). The antenna has a properly crimped end and no stray wires. The line is intact and running out the door and up into the mirror assembly. There was no available mounting area left so I manufactured a aluminum mount and had to use the factory antenna mount as a base to attach my extension. I am wondering if my aluminum mount is the root cause here?Top Secret, I can tell you but then my wife will kill me.

There is a 2 way radio installed in the rig, my antenna mount is sharing the same mount as it's antenna. There is no noise on the antenna line. A quick power up on a second battery gave no noise. It must be somewhere in the grounding of this unit. Next try will be a direct ground to the battery to see what I get. Top Secret, I can tell you but then my wife will kill me.