Is this it? See attached
I think it is probably the ferrite on the audio/power cable...
But if i was able to do something like KENC has here, i would probably go with a ground plane made up of copper or stainless steel rods .
The ground plane would be separated from the transmitter/antenna system both physically and electrically. I guess what im saying is no ground connection would be made between the tx and the ground plane.
See my example image 
Just imagine it as a collar with a bolt in the side to tighten it down to the mast head on the tower just below the tx. I think a 5/8 wave aluminum cb antenna has this as well. Not sure of the brand name.
As for lightning protection for the antenna/tx i would use a lightning arrestor (gas type?) with a separate ground wire isolated from the tower going straight to the earth ground via a copper ground rod.
Still, the ground wire being compliant would be questionable.