[TowerTalk] Impedance difference on 4080V from Cushcraft?

[Dinsterdog@aol.com]

I am going to phase a pair of 4080V verticals by Cushcraft using the W9AD  
multiband phase system sold by WX0B.
 
But before I install the phased system, I am trying to figure  something out 
about the single antenna I have up.
 
My impedance at resonance on 40 meters is 50 ohms with an SWR of 1:1.
 
My impedance at resonance on 80 meters is 40 ohms with an SWR of  1.4:1.
 
I have 20 buried radials averaging 30 feet, some as small as 10 feet, some  
as long as 90 feet crossed over, spreading out in a 40 degree pattern going 
east  away from the antenna which is next to my fence.  I have a real estate  
problem.......
 
If you visit the website at Cushcraft, you can download the  manual.  
 
I am trying to lower the SWR on 80M without effecting 40M. 
 
Since I can no longer lower the resonant point by adjusting the top element  
length, per the manual, I began adjusting the length of the capacitance  rods 
on the 80M hat.   I have spent a lot of time already working with  them.  I 
had success lowering the initial resonant SWR from 2:1 to  1.4:1. But I'm stuck 
there.
 
Should I just be satisfied with the performance or can I do more to improve  
things?  I don't really need anymore bandwidth on 80M. I have around 80KHz  at 
2:1 SWR and I only work the SSB DX window.  If this was only  for 80M, I'd 
use an UNUN to get flat.  But since this is a multiband  
vertical...................................
 
My question is more about theory with the 80M issue than anything  else.  I'm 
just picky-It is just interesting to see the impedance  difference between 
40M and 80M.  
 
Just for FYI, on 40M, I have 280KHz of bandwidth  at 2:1 SWR and I am  flat 
at resonance.  This antenna plays well on an analyzer, hi. 
 
In the rain, I get a 70KHz resonant point drop on both bands- You are  warned 
in the manual but not the sale's brochure- So far, I have had fun with  this 
thing- Can't wait to phase them-
 
73
 
Paul  N0AH