Topband: Detuning/Grounding Xmit Antenna while on RX

[N1BUG]

Can someone explain why grounding the feed of a shunt fed tower 
prevents it from re-radiating noise? The tower is already grounded. 
I don't understand how grounding the coax port looking into the 
gamma or omega match accomplishes the goal.

I've been trying to get my shunt fed tower to stop re-radiating 
noise into my Beverages for 7 years with NO success. I've been 
trying to detune a section of the tower by making a loop with 
capacitor as described in ON4UN's books.

73,
Paul N1BUG