Tom,
When you used to be in Michigan, did the DXCC live where it is 
now?  And did you have the amp. then?  And perhaps you never used the 
wire antenna on twenty because, didn't you have a beam?  Perhaps 
re-orienting the wire would help your situation.  Or not!!
RFI is so hard to pinpoint and remedy.
Pat, K9JAUAt 06:31 PM 2/27/2011, you wrote:
>Hi, all.
>
>First of all, I want to apologize for not being able to hold down net
>control for the Cross-country blind ops net this afternoon.
>
>I seem to have developed an interesting RFI problem with my Alpha Delta DXCC
>antenna, and am trying to troubleshoot it.
>
>You may recall that, several weeks ago, I was unable to tune up my amplifier
>on our 20-meter frequency, because it was tripping off  my Astron RS35 power
>supply.
>
>I solved that problem by grounding the power supply, and by putting RF
>chokes on the DC power cord to the TS480, and the cord that connects my
>surge protector power strip to the AC wall outlet.
>
>Well, apparently, my RFI problems aren't over.
>
>Today, when trying to start the net, I got reports that my audio was
>extremely garbled.  So, needless to say, I spent net time trying to diagnose
>the situation.
>
>I had worked this week-end on setting up a computer at my operating desk, so
>wondered if that was creating ground loop issues for me.  When
>systematically disconnecting the computer stuff, the garbled audio decreased
>significantly, but was still there.
>
>If I took things down to 100 watts, the audio was clear.
>
>I then went down to 40 meters, and made some contacts in the North Carolina
>QSO Party contest.  On 40, even with the amp at 600 watts, my audio was
>reported to be clear and crisp.
>
>So, obviously, I'm getting RF back into the shack on 20 meters with the
>DXCC.
>
>I'm limited here on what I can do outside, since we still have about a foot
>and a half of snow on the ground, but I'd be interested in anything anyone
>could suggest to fix this problem with 20 meters.
>
>I should point out that my rig, amplifier, tuner, and Astron power supply
>are all grounded to the common ground lug on my window feed through panel,
>and the ground lug on that panel is connected to a ground rod right outside
>my shack window.
>
>As I'm sure you can imagine, I am now getting more anxious than ever to get
>my Windom back up.
>
>73 from Tom Behler:  KB8TYJ