Noise grrrr, Sound system noise Options

[insec7]

Ok I got a weird problem that I cant crack. I hear this annoying noise out of my speakers wevery time the car is turned on, the pitch of the noise increases as I rev but it doesnt get louder.
Now I know improper ground causes this to happen, but I know I did ground my head unit properly so the other day I did a little test.


So I took out my head unit, and disconnected the ground from the chasis, but the head unit did not turn off, there was absolutely no change in sound/performance of it.
Then I started disconnecting other cables to figure out what grounding it. Finally when I unplugged the antenna cable, the headunit stopped working, this made me go WTF because it just doesnt make sense (to me anyway) So its obvious that the antenna is causing the noise because it serves as the ground.

Does anyone have any experience with this? Any tips/pointers would be greatly appreciated.

Thanks in advance.