Wednesday, May 18, 2011

Air core inductor

After dispelling my trepidation with a couple practice runs I am now pleased to present my very first air core inductor.  This basic electronic component I constructed from 8 turns of #16 magnet wire.  The diameter of the coil is 1.75".  The yellow pieces are toothpicks temporarily holding the turns of  the coil at a precise .125" spacing.

So what does an inductor do?   

Wikipedia's explanation makes as much sense as anything else I've read.  I've linked directly to the section on air core inductors of which my coil is an example.  This inductor will be the first thing my radio frequency energy reaches after traveling through the transmission line and arriving at the antenna.  The purpose of the coil is to bring the impedance of the antenna as close as possible to that of the 50 Ohm feed line.  Because of the inductor's precarious position at the base of the vertical radiator the coil will be permanently housed in the gray box I discussed in the last post.  Hence the name "matchbox".


  1. Nicely done! Good job with the fiberous 1/8" spacer technology.

  2. Wow, lovely job old man. The sticker really completes the job. Best of 73 de Tom AB9NZ

  3. Thank you for the nice comments! Although it may look like it, I really don't know what I'm doing with this project. This antenna's got lots more going on than a simple dipole.

    The best way to learn is to jump right in and get the hands dirty so thats what I'm doing. Hopefully I can learn a thing or two along the way.