Sunday, May 15, 2011

KD8JHJ Homebrew 40 Meter Vertical Antenna

A steady soaking rain fell all day so I decided to do a little fabrication work on the next phase of my first ever high frequency vertical antenna.  The tasks today involved drilling holes in the 1/4" Lexan match box mounting plate (above left) and fabricating a radial attachment plate.  The radial mounting plate (aluminum piece with the holes and 45 degree bent end tabs) I made from .050" aluminum to provide a sturdy attachment point for four resonant elevated radial wires.

The following photograph shows the components assembled and attached to the base of the antenna radiator.  The box will protect the impedance matching coil and also provide structure to secure the aforementioned radial wires.  A small hole drilled from the inside of the box will allow a stainless sheet metal screw to provide electrical contact from the top of coil to the base of the aluminum radiator. 

At this point I am really starting to get excited and nervous.  The time is drawing near when I will be erecting the antenna in the back yard atop the tripod and with the information gleaned from my antenna analyzer I can begin the tuning process.  I also want to point out that the article from the ARRL Handbook only mentions that a shunting coil is needed at the base of the antenna along with the required turns and diameter of said coil.  So all the engineering and fabrication outlined in this post is of my own design.  

1 comment:

  1. Well, my hat is off to anyone who knows what a shunting coil is ( I certainly don't). You and Sheldon Brown would get along great.