Nomograms: Complex Analog Calculators Simple For Everyone

October 21, 2015 by 29 Comments

In the late 1800s, a railway engineer named Philbert Maurice d’Ocagne was part of a group of men faced with the task of expanding the French rail system. Before a single rail could be laid, the intended path had to be laid out and the terrain made level. This type of engineering involves a lot of cut and fill calculations, which determine where dirt must be added or removed. The goal of earthwork is to create a gentle grade and to minimize the work needed to create embankments.

In the course of the project, d’Ocagne came up with an elegant, reusable solution to quickly  solve these critical calculations. Most impressively, he did it with little more than a pen, some paper, and a straightedge. By developing and using a method which he called nomography, d’Ocagne was able to perform all the necessary calculations that made the gentle curves and slopes of the French railway possible.

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Winding Your Own Small Coils

February 22, 2022 by 18 Comments

Depending on what you build, you may or may not run into a lot of inductors. If you need small value coils, it is easy to make good-looking coils, and [JohnAudioTech] shows you how. Of course, doing the winding itself isn’t that hard, but you do need to know how to estimate the number of turns you need and how to validate the coil by measurement.

[John] uses a variety of techniques to estimate and measure his coils ranging from math to using an oscilloscope. He even uses an old-fashioned nomogram from a Radio Shack databook circa 1972.

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Sign Of The Smith Chart Times

May 13, 2018 by 5 Comments

The Smith chart is a staple for analyzing complex impedance. [W2AEW] notes that a lot of inexpensive test gear like the MFJ-259B gives you complex readings, but fails to provide the sign of the imaginary part of the complex number. That makes it difficult to plot the results on a Smith chart or carry out other analysis. As you might expect, though, he has a solution for you that you can see in the video, below.

A common method is to increase the frequency slightly. In a simple case, you’d expect the imaginary part — the reactance — to go down for a capacitive impedance and up for an inductive one. Unfortunately, this doesn’t apply in many common cases, including when you are measuring through a transmission line which is probably what most people are doing with this type of test gear.

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Antenna Basics By Whiteboard

September 11, 2017 by 16 Comments

Like a lot of people, [Bruce] likes radio controlled (RC) vehicles. In fact, many people get started in electronics motivated by their interest in RC. Maybe that’s why [Bruce] did a video about antenna basics where he spends a little more than a half hour discussing antennas. You can see the video below.

[Bruce] avoids any complex math and focuses more on intuition about antennas, which we like. Why does it matter that antennas are cut to a certain length? [Bruce] explains it using a swing and a grandfather clock as an analogy. Why do some antennas have gain? Why is polarization important? [Bruce] covers all of this and more. There’s even a simple experiment you can do with a meter and a magnet that he demonstrates.

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Start Your Path To Becoming An Antenna Guru

November 27, 2016 by 15 Comments

We’ve known a few people over the years that have some secret insight into antennas. To most of us, though, it is somewhat of a black art (which explains all the quasi-science antennas made out of improbable elements you can find on the web). There was a time when only the hams and the RF nerds cared about antennas, but these days wireless is everywhere: cell phones, WiFi, Bluetooth, and even RF remote controls all live and die based on their antennas.

You can find a lot of high-powered math discussions about antennas full of Maxwell’s equations, spherical integration and other high-power calculus, and lots of arcane diagrams. [Mark Hughes] recently posted a two-part introduction to antennas that has less math and more animated images, which is fine with us (when you are done with the first part, check out part two). He’s also included a video which you can find below.

The first part is fairly simple with a discussion of history and electromagnetics. However, it also talks about superposition, reflection, and standing wave ratio. Part two, though, goes into radiation patterns and gain. Overall, it is a great gateway to a relatively arcane art.

We’ve talked about Smith charts before, which are probably the next logical step for the apprentice antenna wizard. We also covered PCB antenna design.

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