Foundations of Amateur Radio

Recently I discussed the concept of a VFO, a Variable Frequency Oscillator. It's an essential building block for our amateur radio community. In describing the idea behind it, while making an error in one of the CB radio frequencies, thanks to Ben VK6NCB for picking that up, I skirted around how a VFO actually works.

In reality the VFO is a collective term that describes a whole range of different methods to vary a frequency. Naturally I continued my exploration and discovered a whole range of documentation on the subject. I even started writing about how one common method, a Phase Locked Loop or PLL, works and how a VCO, a Voltage Controlled Oscillator, operates as part of that. I'll come back to those shortly.

In doing my reading, since, as is often the case, I use my weekly contribution to the world as a method to learn things. I'll investigate a topic and attempt to describe who came up with it, what it means, how it works and what its place is in the world, the who, where, why and what of it, if you like. I suspect that comes from my very first introduction to broadcast radio where that was one of the very first things I was taught, thirty years or so ago.

If you've followed along for the decade I've been at this you'll know that I also intersperse such learning with observations about the things that I'm interested in. This is such an observation, a meta view if you will.

I discovered somewhat to my chagrin that the ways that an essential component of our hobby, a system called a Phase Locked Loop, was described in such academic terms, complete with formulas and detailed circuits and even component lists, spread over pages and pages of verbiage, or explained in YouTube videos lasting an hour or more. Of course there were some little gems, ElectronicNotes on YouTube manages to cover the basics in little over six minutes, but that's a rare example.

It reminded me of a website that I've been using to fill in the gaps in my understanding of SDR or Software Defined Radio and Digital Signal Processing or DSP. The PySDR.org site is an online textbook written by Dr. Marc Lichtman. He says about his method: "Instead of burying ourselves in equations, an abundance of images and animations are used to help convey the concepts [...]"

My weekly efforts have always attempted to do exactly that and I found myself in a place where such a thing didn't appear to exist for the concepts behind the PLL and VCO. My obvious response to that would be to write the missing document and as I said, I have a first draft of it sitting on my computer.

There's only one problem.

I don't yet "grok" the concepts. If you're unfamiliar with what grokking is, it means to understand intuitively and emphatically. It also means that unless I can describe it in less than a single page of A4 paper I don't understand what I'm saying and you'll get bored waiting for me to make a point.

Here's my point.

How do you learn concepts? What is it that you do to discover new topics of interest and how do you progress through the various stages between discovery and grokking?

For me it's about puzzle pieces. It's always been puzzle pieces. Little nuggets of information, almost trivial on their own, but after a while you get to a point where you have enough of them that you can start joining them together to grasp a more complex concept.

Here's a puzzle piece I discovered today.

Impedance: The difference between an explosion in air and one under water is impedance.

It's little concepts like that which make me get out of bed and discover what's on the horizon next. I'm also learning about double and triple conversion superheterodyne radio which I believe has a one-on-one parallel application in Software Defined Radio and Digital Signal Processing. Once I figure out how to describe it to you, I'll let you know.

The point of all this is that learning things is as much about understanding as it is about explaining.

Feel free to point me at new and interesting basic concepts.

I'm Onno VK6FLAB