[Antennas] Velocity factor for wire?

[Chris Jensen]

Hi All 
I am looking for the approx velocity factor for 1.5 mm solid Cu.wire ,
it is insulated with clear paint ( same type being used in a 230 to
18volt mains transformer)

What kind of wire and size is Orr using in his book, all about cubical
quad? 

When I design the loops after his Formula 1004/f  , I get using my
cubber wire a somehow lower resonance frequency , than center of band.

best vy73 de oz1bxn chris