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AJ8MH's Notebook Series - Homebrew Balanced Tuner
Ideas... 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 do work with my configuration, which is a 44 foot inverted-vee with about 35 feet of 300 ohm
ladder line running into the shack.
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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.
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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.
Have fun with your project and 73.
Joe ( AJ8MH ) aj8mh@arrl.net
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