# Microwave Nomographs

Back in the days before everyone carried a computer in their pocket, if you wanted to perform complex calculations you had two choices: you could do the math by hand, which was time consuming and error prone, OR you could use a nomograph (sometimes called nomogram) to get a quick answer. Nomographs were often printed in magazines, or sometimes on laminated cards that you could pick up at conferences. What's a nomograph, you say? It's a little bit like a paper-based slide rule, where you have the possible numbers you want to manipulate laid out in a specific order, and the possible answers printed a carefully calculated distance away. Then you could draw a line through two columns to hit the solution on the third. Fast! Easy! and for most applications, Good Enough!

Note that nomographs are distinct from a very similar tool (of similar vintage) where instead of moving your ruler across columns of numbers, you actually move the printed numbers so that they move through little windows in a frame. Check them out over on our Old School Tools page!

Our new friend Paul just happened to find these things so useful that he saved some samples from the 1960s, and he was kind enough to let us share them (see below). Thank you, Paul!

These beauties take up a bit of room, so here's a list of the ones we've included here. Have more of your own to contribute? Let us know!

Coaxial Line Impedance Calculator

Noise Figure for Cascaded Amplifiers

Up first, a quick way to calculate skin effect from Electronic Design magazine, 1965:

This next one gets a little bit more complicated, but it's still quicker than using a pen and pencil to do the math. Also from Electronic Design magazine, 1965:

Here's a coaxial line impedance calculator - all you need is a straight edge! From Electronics and Communications magazine, 1967

Equivalent values of dB, dBm below 3 from Electronics and Communications magazine, 1968

Noise figures for cascaded amplifiers, from Electronics and Communications magazine, 1968

**Source : **Archives of Paul Chorney