eHam Forums => Elmers => Topic started by: K5LDL on April 20, 2012, 09:09:56 AM

Title: Induction Coil(s?)
Post by: K5LDL on April 20, 2012, 09:09:56 AM
Hello again!

While contemplating my induction coil set ups for my 2 vehicles and their respective antennas, a Sierra Sidekick and a Bug Catcher, and exploring the Net for ideas and answers, I came across a few commercial sites that sell ready made induction coil matching units.  Some are bare enamel wire, others are housed in PVC caps, some are wrapped around a PVC mold and covered in epoxy or some silicone goop, and some are housed in gray PVC electrical boxes.  While some folks use only one coil to work 40 and 80 meters,  I came across a manufacturer, whose name eludes me now, who markets a gray PVC box with two coils inside of it.  It fascinated me, however I didn't bookmark the site nor can I remember its name! 

What I wanted to see more than anything is how the coils were connected inside the box and thus how it was mounted and connected to the antenna.  Also, would there be any interaction between the two coils as one uses 40m or 80m.

If anyone knows of this manufacturer or the answers to my questions, please enlighten me!

As always, 73!

Luis K5LDL ex KD5KJD

Title: RE: Induction Coil(s?)
Post by: W5FYI on April 20, 2012, 09:27:01 AM
I guess I'm not keeping up with technology! I know what induction is, but what are induction coils for antennas?  I'm more familiar with loading coils, matching coils, choke coils and tuning coils. What is it that induction coils are suppose to do?

Added: After rereading your description of these induction coils, I think you are referring to baluns. Balun, a contraction of "balanced-unbalanced," are special transformers used to match unbalanced transmission line (e.g. coax) to balanced antennas (typically, dipoles). They can also be used to match balanced transmission line, so-called ladder line, to unbalanced antennas, such as your verticals. If you want to use coax with an unbalanced antenna, such as your vertical, the transformer is called an unun (for unbalanced-unbalanced).

The Cebik antenna site ( has a good discussion on baluns, ununs, and other antenna transformers, and a search of eHam should turn up various articles about their construction and use. You can also google the terms and find numerous more discussions. Jerry Sevick and Doug DeMaw have written books describing them, and there is also a good discussion in the ARRL Handbook and Antenna Book.

I hope I interpreted your question correctly. Good luck.

Title: RE: Induction Coil(s?)
Post by: W0BTU on April 20, 2012, 10:05:56 AM
An induction coil is an old design used for generating high voltage. They aren't used on antennas.

Title: RE: Induction Coil(s?)
Post by: K5LDL on April 20, 2012, 12:44:12 PM
Maybe I should have clarified the title?  These are known as shunt matching coils, inductive matching coils, matching coils. 

Title: RE: Induction Coil(s?)
Post by: K5LDL on April 20, 2012, 12:46:37 PM
I'll re-post in other Forums, Antennas and Mobile.