Learning About VNAs

We live in a good time to be an electronics geek. It used to be only the richest or shrewdest among us had a really good oscilloscope, while these days it is entirely feasible to have a scope that would have cost a fortune a few decades ago, a logic analyzer, arbitrary waveform generator, and what would have once been a supercomputer and still not be in debt. One of the cooler pieces of gear for people working on RF electronics is a vector network analyzer (VNA) which used to be exotic, but now can be bought for very little. But what do you do with it? [W2AEW] has the answer.

We always look forward to a video from [W2AEW]. Even if we know about the subject he covers, we usually pick up something new or interesting. Like all of his videos, this one is intensely practical. Not a lot of drawing but plenty of scope shots and experimenting.

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Diode Basics By [W2AEW]

We didn’t think we needed a basic guide to diodes until we saw it was from [W2AEW], and then we knew we’d pick up some new things. Entitled “Diodes from Ideal to Real” the 18-minute video doesn’t disappoint with a mix of notes and time with a curve tracer to learn all about these devices.

As is typical for a [W2AEW] video this doesn’t just cover the simple operation of diode. It includes topics such as dynamic resistance, junction capacitance, and talks about a wide variety of diode types.

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Zener Diode Tutorial

We always enjoy [w2aew’s] videos, and his latest on zener diodes is no exception. In it, he asserts that all Zener diodes are not created equal. Why? You’ll have to watch the video below to find out.

Zener diodes are one of those strange items that have several uses but are not as popular as they once were. There was a time when the Zener was a reasonable way to regulate a voltage inexpensively and easily. Unfortunately the regulation characteristics were not very good, and the power lost was very high. But that was sometimes a reasonable trade, compared to putting a pass transistor and the associated discrete circuitry in place to make a linear regulator. With the advent of chips like the 7800-series regulators, you can have a high-quality regulator with one extra wire and still keep your costs under $1. Even if you want to do better and go with a switching power supply, that’s easy now and not much more expensive.

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Sign Of The Smith Chart Times

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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[Alan Wolke]’s How To Use An Oscilloscope

If you were to create a Venn diagram of Hackaday readers and oscilloscope owners the chances are the there would be a very significant intersection of the two sets. Whether the instrument in question is a decades-old CRT workhorse or a shiny modern digital ‘scope, it’s probably something you’ll use pretty often and you’ll be very familiar with its operation.

An oscilloscope is a very complex instrument containing a huge number of features. Modern ‘scopes in particular bring capabilities through software unimaginable only a few years ago. So when you look at your ‘scope, do you really know how to use its every feature? Are you getting the best from it, or are you only scratching the surface of what it can do?

[Alan Wolke, W2AEW] is an application engineer at Tektronix, so as you might expect when it comes to oscilloscopes he knows a thing or two about them. He’s spoken on the subject in the past with his “Scopes for Dopes” lecture, and his latest video is a presentation to the NJ Antique Radio Club which is a very thorough exploration of using an oscilloscope. The video is below the break and at an hour and twenty minutes it’s a long one. We make no apologies for that, for it should be fascinating in its entirety for any oscilloscope owner. Even if you find yourself nodding along to most of what he’s saying there are sure to be pearls of ‘scope wisdom in there you weren’t aware of.

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