Topband: insulated vs:bare radial wires

[Jim Hoge <knowkode@sbcglobal.net>]

Greetings,
 
Can I expect any noticable difference using an insulated wire for radials? 
Theoretically, the velocity factor of the insulation will make the physical 
length shorter but is a tuned 1/4 wave radial length that important when it 
is buried or laid on ground? The plan is to use 18ga awb, of which I have some 
30k feet at my disposal. 
 
tnx,
Jim W5QM
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160 meters is a serious band, it should be treated with respect. - TF4M