The addition of 160 m radials will do little to the Z11 on 80 meters 
especially if you have a good radial system in place for 80 meters. I 
went thru the same with my 4 square on 80 meters. I added 160 meter 
operation for the array by using the NE/SW diagonal elements as a 2 
el array on 160 meters. I noted a slight change in the Z11 on 80 
meters as I added 160 meter radials to the two diagonal elements, but 
it was in the order of 2 ohms. Since the 80 meter Z11s of the 
elements vary by that amount anyway, I did not let it over concern 
me. I have measured the Z11 impedance of a number of vertical arrays, 
and seldom do the Z11s of the elements fall within 1 ohm. They often 
vary by as much as 5 ohms or more. I would suggest you measure the 
Z11s (at resonance) of your two elements and if possible add 160 
meter operation to the one with the larger Z11 if it concerns you. 

The currents in the two elements are the important thing. Z11 effects 
the current I agree, but the effect of 1-2 ohms is minimal to the 
pattern. What from a practical standpoint what is usually of more 
importance, especially for short elements, is that the  Z11 resonant 
freq of the elements be the same. 

Robye W1MK     


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