Topband: detuning shunt fed tower

[N1BUG]

I have made numerous attempts to "detune" my vertical over the past 
6 years. I admit at this point I have no idea what I did wrong or 
what to try next. I have what I believe to be evidence the vertical 
is interacting significantly with the several Beverages, which of 
necessity are close to it. I attempted to follow the advice in "Low 
Band DXing" and on W8JI's outstanding web site but I didn't get very 
far.

The vertical is 100 feet of Rohn 25 tower with a ~30 foot long 7 
element 6 meter beam sitting at 103 feet. There are approximately 
100 on-ground radials ranging from 60 to 200 feet in length. It is 
gamma matched by a 4.5 inch triangle of #6 wires spaced 
approximately 30 inches off one side of the tower. The short is at 
about 32 feet (from memory, may be off a couple of feet in either 
direction), BUT the 3 wire gamma "rod" continues to approximately 
the 60 foot level. Is this a problem? Should I get rid of the 
"excess" length of the gamma match?

Previous attempts to detune the vertical ended in frustration. First 
I attempted to use the gamma match as the loop since that would be 
very convenient. Using an MFJ-259B I was able to get the loop down 
to about 2 ohms. This occurred with about ~900 pf capacitance vs the 
few thousand pf I was expecting. It did not seem to have any 
noticeable affect on what I presume to be vertical / Beverage 
interaction. I tried the same thing with a similar sized loop placed 
half way up the vertical on the side opposite the gamma match, with 
similar results.

Perhaps I am wrong about the nature of the problem? Local noises 
(eg. plasma TV) don't change by the expected amount (F/B of 
Beverages) when I switch among Beverages. Often, while listening to 
such a noise on one Beverage, switching from the vertical to a 
different transmit antenna (thus leaving the ~250 feet of coax 
feeding the vertical open at the shack end), there will be a 
dramatic change in noise on the Beverage, depending on the 
particular noise and Beverage selected. I take this as evidence the 
vertical is re-radiating noise and that detuning it should help. Is 
that a valid assumption?

Is there any other method I can use to detune the vertical? How 
about listening to a signal coming from the back of a Beverage and 
tuning the vertical decoupling section for minimum signal on the 
Beverage? Would that be valid? Any other ideas?

Noise is getting out of hand around here. Every time I listen there 
seems to be a new one. Of course I will continue to track them down 
and attempt to mitigate at the source. But the need to get my 
station receive performance as good as it can be has never been more 
evident.

73,
Paul N1BUG