KØFF Homebrew Tips
Subject: Make Your Own Loading Coils DE KØFF
OR: "If they look like DUX and walk like DUX and quack like DUX, maybe they
ARE DUX"
(then again maybe not)
"Air Dux" inductors were once plentiful and inexpensive. Not so today. Even if they were, HAMs
like to make their own apparatus when possible. Here is one method that I have long used to
make evenly spaced, nice looking coils of all sizes.
Make your own loading coils for antenna projects using Caterpillar Grommet
strips. Also called flexible grommets, flexible bushings etc.
These are used by installers to form protective bushings around the edges of holes cut into sheet metal,
and come in strips that are cut to desired length then snapped into the hole to cover the raw edge.
We used to use them when installing 2-way radios to line the holes we made in the firewall to pass the heavy 12V wires.
The evenly spaced notches make an ideal form and support for AIR DUX knockoffs. Use Duco or Testors model
cement to secure the wires in the strips before removing from the temporary
forms. Nylon Grommet strips can be purchased at McMasters, as well as many other supply houses.
Fig 1 is the caterpillar grommet material as purchased from the supplier:
Fig 2 - Next Wrap the form (whatever size you need) in wax paper and temporarily
tape the plastic strips on there:
Fig 3 -Wind the coil using the notches as a guide. Seat the wire all the way down
strips when the coil is wound:
Fig. 4 - When the glue is dry, slip the assembly off the form and trim the strips to
correct length:
Fig 5 - Any size diameter or length can be wound, just use bigger forms and more
strips: