LDG Balun User Manual

LDG Balun and Unun
User's Manual
Introduction
Congratulations on your purchase of an LDG Balun or Unun. These quality units greatly expand
the utility of your LDG Automatic Tuner, allowing much greater flexibility in the type of antenna
and transmission line you can use. LDG's Baluns and Ununs are inspired by the designs of Jerry
Sevick, W2FMI (SK) in his classic book Transmission Line Transformers.
All LDG Baluns and Ununs are rated at 200 watts PEP from 1 to 30 MHz, and are water resistant;
they are intended for outdoor use. Each weighs 6 oz, and measure 5"x2.5"x1.2".
Baluns and Ununs
Balanced antennas are electrically symmetrical and do not rely on connection to the ground; an
ordinary dipole is a good example of a balanced antenna. Unbalanced antennas are asymmetrical
and rely on a ground, such as a ¼ wave vertical antenna operated against a ground plane. All
modern radios have unbalanced outputs, and all coaxial cable is unbalanced.
Feeding a balanced antenna with an unbalanced transmission line can lead to unwanted RF
current distribution that degrades performance. Baluns are circuits that match an unbalanced
transmission line to a balanced load, and can adjust the impedance ratio as needed. Ununs match
unbalanced transmission lines to unbalanced loads, also adjusting impedance.
RBA-1:1
The RBA-1:1 is a 1:1 Balun designed to allow easy interface to Dipoles,
Inverted Vees and other center insulated wire antennas. The Balun can
operate "stand alone", or it can be used with an LDG Automatic Tuner. It
may be used with any of your dipole, random, ladder line or balanced
antenna projects. Connection is made by 5-way, twist-on binding posts.
RBA-4:1
The RBA-4:1 is a 4:1 Balun that allows your LDG Automatic Antenna Tuner
to easily match an antenna fed with Twin-lead or Ladder-line. The Balun
can also operates "stand alone" without a Tuner. It may be used with any
twin-lead or ladder-line antenna projects. Connection is made by 5-way,
twist-on binding posts.