antenna light comes on when talking

sounds like you still have a ground issue

 

Noman, explain in a bit more detail about the problem if you can,
Where are the power and ground wires going to ?
Where and how is the antenna mounted ?
How is the cable routed to the radio from the antenna ?

 

My question would be, what is the length of the jumper between the amp and the radio? The size of the cable has no bearing on the issue, LMR400 is extreme to say the least, but, as long as it's an RG58/59 or 8 of some kind you're fine, but, I'd like to know the length of the jumper. Is it straight or do you have it coiled up? If it's straight, coil it up and tie it together to create an "RF Choke" in the line. If it's more than 3 foot, get a shorter cable if possible.

 

Last I knew RG-59 was 75 ohm coaxial cable.

 

The visegrip mount on mirror mount could be the problem. You could have a bad ground and/or your SWR is high. Check both first.

 

Noman
Where are you taking your SWR Readings, so far you havent mentioned an inline meter. Are you taking your SWR readings from the radio's meter itself ?
Just so we can be sure we are all on the same page here.
Do you have access to a dummy load or possibly a friend who has an antenna to see if the AWI light comes on; you will know that the radio is out of adjustment -and it is reading incorrectly.
Just a thought...