Naf,
RST Engineering at tech@rst-engr.com or www.rst-engr.com  publishes a neat
35 page pamphlet "The RST-802 Antenna Reference Text".  Contact Jim there to
purchase one.  Maybe Marv's book store has it.
Ferrire beads or Baluns (BALanced/UNbalanced) (rymes with Alan) matches a
balanced dipole antenna to an unbalanced coaxial cable.  Ferrite beads are
one type of balun.
Install the beads over the coax at the antenna end just short of the first
removed insulation.  Use three beads spaced about 1/4" apart and using
silicone RTV and shrink lock them in place there.
I have read and reread Jim's pamphlet as it is full of good stuff for your
aircraft radio/antenna installation.  There are designs for home made
antennas, splitters and baluns also.
I have many extra beads I could sell an my cost.
Walter Dodson
wdodson@bak.rr.com