Butternut advertises a multiband (40,20,15,10) resonant radial system
(model STK) for use with their verticals. It is made from twinlead,
with notches in it.

See http://www.bencher.com/pdfs/00361ZZV.pdf

How does this work? Is there design information available anywhere so
one could build their own system for other bands?
How does its performance compare with normal radials?
Bandwidth, efficiency etc.

Bob W8ERD