I put together a radial system for my 5 band trapped vertical antenna. I’m using (32) 16.25′ radials, soldered to a 10 gauge bare copper wire. The copper ring will connect to the 3 bolts at the base of the vertical. For wire, I purchased a 500′ roll of underground dog fence wire at Home Depot. Each wire will be buried just below the surface in a star burst pattern. I used the ARRL antenna book to calculate the optimal radial system for the amount of wire I have.

5BTV radial wire