Notebook Series - Homebrew Balanced Tuner Ideas
[ Austin, TX ] The web has many references to balanced tuners, and some building plans shown are more complicated than others. The diagram below shows the basic idea, and you can work from it to build your tuner.
There aren't any step-by-step instructions here, so roll your own. Building these tuners isn't complicated, but please remember that the impedance presented at the turner depends on many things including feed-line length. These tuners have been tested with 44 and 88 foot inverted-vees with about 35 feet of 300 ohm ladder line.
The photographs show two tuners I built on wood. The total inductance is larger on one, but the variable capacitor used with both tuners is about 500 pf or more. The larger tuner covers 80 through 10 (not tried on 160 meters). The 18 turn choke is wound on a PVC form. You can see the small knife switch between the coils to move the cap from the input of the coils to the output.
The smaller tuner covers 40 through 10 (not tried on 80 meters). The 12 turn choke is made with enamel coated wire and is wound on a core. I did this just to save space. You could probably get away with using zip cord or simply winding RG-58 around the core. Using coax presents some problems as it's difficult to keep the turns tight against the core. A switch isn't used with this version. All connections are made using alligator clips.
ex: WPE8EUM, WN8AQL, WB5FCO and WJ5MH