There are two general classes of balun: voltage and current. Voltage baluns place an inductance
across the load, and present an equal RF voltage on both sides of the balanced output. This
creates a balanced RF current in each side of the load in the degree that they are electrically
equal. Current baluns do not place an inductance across the load, and present an equal current in
each side of the balanced output over a somewhat wider range of conditions. Current baluns also
have a somewhat wider bandwidth. The LDG RBA-1:1 is a current balun, while the RBA-1 is a
voltage balun.
Your LDG balun consists of two bi-filar windings of heavy insulated wire on a toroid core of
high-permeability ferrite. These windings form a low-loss transformer that performs the
balanced-to-unbalanced conversion, and in the case of the RBA-1, acts as a 4:1 impedance
matching transformer as well.
Bifilar turns #18 insulated
wire on FT-125 toroid coil
SO-239 coax
connector
Balanced
Unbalanced
Binding post
connectors
RBA-1
8
