You don't put down a lot of radials only for more return current; you
put down a lot also because over time you'll probably lose some of
them to damage or decreased conductivity or some form of disturbance.
If your radial field is uncontrolled, and you can't watch it
constantly, you may wind up with a doggie digging up and chewing on
one, or who knows what else. The assumption is that you want to do
this once and have a ground system that will last for decades. You
also put down a lot of radials so that the return current on each one
is less. When you have enough, you will no longer need to fool around
with "ununs" and other ferrite contrivances because 98% of the RF will
be on the radials instead of your feedline exterior.
If you have an inverted L that's the classic vertical length, around
60 feet high and 60 or more feet horizontal, (you can put bends in the
horizontal part provided they are over 90 degrees) your feedpoint
impedance should be low--10 to 20 ohms. If it is higher than that,
you need more radials.
Are there out buildings in your ground system or on its periphery? If
they have metal--aluminum siding and/or a steel roof, you should strap
them into your ground system using brass clamps and copper strap below
grade back to your radial junction.
What if such a structure is RF transparent but smack inside where you
want radials to go? You need to put copper strap along the
foundation all the way around the structure and bond the interrupted
radials to the strap, continuing in lines out the other side.
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