What is Amplitude Modulation?

In this next series of posts, we’re going to dive into the heart of the radio arts: modulation.  Modulation is what make wireless communications possible.  Over the years, many different ways to modulate signals have been created.  The advent of digital electronics has brought along with it a slew of new digital modulation techniques as … Read more

Active Mixers in RF Design

Our first post on mixers focused on essential mixer theory and passive mixers.  Understanding the diode double-balanced mixer is a great start, but that still leaves many mixer architectures unexplored.  Some of the most popular mixers used in to today’s commercial and amateur gear are active mixers, and it makes sense to dissect the more … Read more

Mixers in RF Design

Mixers are a fundamental component in all RF communications equipment.  They are required for nearly all modulation schemes, and have been present in radio in some or another since the beginning.  Radio would not be possible without the existence of mixers.  Despite their importance in radio equipment, many hams and experimenters are intimidated by them … Read more

OSC II.1 – The Phase-Locked Loop

The Phase-Locked Loop (PLL) is one the most popular building blocks of any RF system.  Understanding the PLL unlocks many possibilities for the experimenter, however many hobbyists and those relatively new to electronics are put off by its apparent complexity.  While PLLs can seem daunting, by understanding the main principle behind PLL theory and dissecting … Read more

OSC I.2 – Quartz Oscillators

Introduction No component is as connected to ham radio history than the quartz crystal.  Still today, thanks to their excellent frequency stability and cost-effectiveness, crystal oscillators in one form or another dominate the electronic landscape.  You’ll find them in nearly every electronic device you can think of, from PC motherboards to your wristwatch.  And, of … Read more

OSC I.1 – LC Oscillators

While it is true that at first glance oscillator circuits can seem complicated, in truth, despite the hundreds of different oscillator designs available, they are all derived from just a few possible architectures.  Knowing the fundamental theory and architecture behind oscillator circuits will allow you to make sense of most oscillator designs, and also allow you to design your own.

FIL I.4 – Active Filters

In the previous post we went over passive LC filter design.  LC filters do have many advantages: they are simple to understand and design and they don’t require an external power supply.  They also are the only solution for higher frequencies.  That said, they cannot provide gain.  Instead, some power is lost when the signal goes…

FIL I.3 – Filter Design Basics

The math behind filter design is actually very complex, and the equations that determine component values are complicated.  Fortunately, most of that complexity will be transparent to you!  Good news, you’ll never have to work from scratch when designing filters.  Instead, filter design relies on using tables of normalized values, then extrapolating these values…