Everything for Electronics

# Theory

#### A Discussion on dBs and RF Power Meters

This article discusses basic theory on the decibel unit and its role in electrical measurements of power, etc. It also describes the construction of an RF power meter which in the past has been difficult to use and expensive to own. With the breakthrough of new ICs in recent years, most of the former problems and expense have been eliminated. This is a simple and inexpensive unit to build, but has the accuracy, resolution, and dynamic range that was only obtainable in lab quality test equipment a decade or so ago. This kind of test equipment is almost mandatory for amateurs, radio frequency work, or test equipment calibration. Also, when built as described, it’s a very professional looking piece of gear that anyone would be proud to display on their test bench.

#### An Elegant Approach to Design a Variable Voltage Divider

A voltage divider is probably the most common electronic circuit. Despite its simplicity, it can be a design challenge for many folks, particularly beginners. This article presents a fast and accurate way to design a variable voltage divider with minimum math.

#### Mass Confusion: The End of the Kilogram as We Know It

This November, in Versailles, France, representatives from 57 countries are expected to make history. They will vote to dramatically transform the international system that underpins global science and trade. This single action will finally realize scientists’ 150 year dream of a measurement system based entirely on fundamental properties of nature. The International System of Units — informally known as the metric system — will change in a way that is more profound than anything since its establishment following the French Revolution.

#### Can You Trust Your Voltmeter?

Sometimes I wonder which of my portable digital voltmeters I can trust — the B&K, Fluke, or Amprobe. Usually, they’re pretty close but it bugs me not knowing whether they are right on the nose. Fortunately, these days, there are a number of very accurate voltage reference circuits that you can build or purchase for a few dollars.

#### How Phased Array Antennas Work

Phased arrays have been used for years in military radars for long range detection of missiles. They’re also widely used in military and commercial aircraft radars and some satellites. These phased arrays are expensive, but today thanks to new technology and higher frequencies, phased arrays are smaller and more affordable making them practical for new wireless devices. This article is an introductory tutorial on this special antenna type you need to know about.

#### Filter Design Software

Filters are one of the most important and widely-used circuits in all of radio at any frequency.  Understanding how they are specified and used will make you a better electronics designer, whether you build your own or simply buy them from a vendor.

#### Does Inductor Winding Have You Tied in Knots?

While resistors and capacitors are easily procured and stocked, most RF circuits require inductors in a wide range of very specific values. In most cases, you need to create these yourself. Here are the principles behind inductance and some tricks that I’ve used to make my own inductors.