March 1955 Popular Electronics

## March 1955 Popular Electronics[Table of Contents]People old and young enjoy waxing nostalgic about and learning some of the history of early electronics. Popular
Electronics was published from October 1954 through April 1985. All copyrights are hereby acknowledged. See all articles from
Popular Electronics. |

Single layer coil design charts (aka nomographs) are a dime a dozen on the Internet. Here is RF Cafe's 0.083¢ contribution. A couple examples of usage are included. You're welcome.

This chart can be used to find inductance of a coil when dimensions and number of turns are known, or to find
specifications to give a desired Inductance. Draw a line between either T and L or d and
*l*/d, whichever are both known. Draw
a second line between remaining known quantity and point of intersection of first line and unmarked vertical line.
Extend second line to scale for unknown quantity and read answer.

EXAMPLE A: We have a coil 5" in diameter, 19 turns, 37 turns per inch, and wish to find the inductance.
*l *= 19/37" = .52";
*l*/d = .52/5 = .104.
Draw a line between d=5 and *l*/d = .104.
Draw a second line from T = 37
through the intersection point to the L scale. Read the answer, 100 microhenries.

EXAMPLE B: We require the number of turns of a coil 5" in diameter, wound 37 turns per inch, to give 100 microhenries.
Draw a line between T = 37
and L = 100.
Draw a second line from d = 5,
through the intersection point, to the *l*/d
scale, and read *l*/d = .104.
Then *l* = 5 x .104 = .52
Inches. The number of turns is .52 x 37 = 19,
approximately.

**Single Layer Coil Design Chart**

Posted April 16, 2013