Welcome to W2BRI's Magnetic Loops

Images and Notes from Other Loop Builders, Inventors, and Enthusiasts

 
You Can Build it Too
With Some Slight Modifications an Easy to Build Loop Can be Yours

By John Gbur, N3KNZ

       
      I have been a ham for 12 years. I was interested in Amateur radio and electronics since I was 5 but didn't get my license until I was out of college. I got sidetracked playing with computers which is a good thing because that led to my career working with computers.

I have always been interested in building things including antennas and radio kits. I finally broke down and purchased an MFJ analyzer recently.  This has  helped out tremendously in my antenna projects.  I have experimented with stealth dipoles, vertical wire antennas and most recently got interested in  loops about a month ago.  This article describes the first loop that I made. I have several more loops planned and already have the tubing cut for them. There are a wealth of loop plans and information on the web, go ahead give one a  try!
The magnetic loop antenna I built was from an ARRL article: "You Can Build A Compact Loop Antenna for 30 Through 12 Meters", QST, May 1994, p33.  You can contact the ARRL for a reprint of the article.  Or if you are a league member just download the PDF file from the website 

http://www.arrl.org/members-only/tis/info/pdf/9405033.pdf.

I modified mine slightly from the original version.  I used 1" copper mounting straps as connector points for the capacitor stub and the shield connection on the main loop.  These are clamped in place with a nut, but will be soldered in place for the final version.  Also instead of using a variable capacitor, I used a coaxial stub capacitor.  This let me get started without ordering the capacitors. I plan to order some variable and possibly vacum variable
capacitors in the future.

I really liked the PVC mast in the article.  It dissasembles into five pieces

1) The Top mast portion with the loop mounted to it.
2) The bottom mast portion that attaches to the base.
3) Left base
4) Right base
5) Center base
(All three base sections connect to form an H).

I used crimp on connectors (execpt for the PL259) and a good ratchet crimper. I am going to solder them, but for my initial road test I just left them crimped.

As with any antenna an antenna analyzer is invaluable in setting up any antenna system.   I used an MFJ analyzer to do my setup.

My initial testing was done in the evening when 20m was not in that great of shape.  Using my FT-817 and 5 watts on PSK31 I was able to make my first contact  to Azores Island.  Not bad for 5 watts into a loop 8 feet off the
ground on my deck!

My next plans are to work on a remotely tuned capacitor setup and build some more square loops out of  half inch and one inch copper tubing.

Have fun,   73's  N3KNZ
 

 Back to Home Page