Topband: One More Radial Question

[Wayne Rogers]

I've been reading, and still haven't come up with an answer to the following question:  

With radials laid on the ground, does it make any difference if they are insulated (THHN) or bare?  I suspect not, but would like to know that I am not making a bad assumption.  Seems that even the most recent works in this area don't talk about the difference between "laying wire on the ground" and copper wire directly in contact with earth.  Conceptually I understand that the wire laid on the ground is capacitatively coupled to the earth, but how does the effect of this translate to the decision to use bare vs. insulated wire?

I have six 1/4 wave radials (THHN) on the ground and will continue to add shorter radials interspersed between them.  I can work Europe (barely) with my 100 watts, but know I can do better.  Thanks to all for the many posts and sharing your wisdom.

Wayne, N1WR