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Foundations of Amateur Radio #209:

from Onno VK6FLAB on June 9, 2019
Website: http://vk6flab.com/
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When digging gives you more understanding, the magic of software.

Today I'm going to go sideways to move forward. In amateur radio we consider circuits, components such as transistors, inductors, capacitors, crystals and how they're connected to each other. The framework in which that exists is embodied by the field of electronics and how these components can be mixed together to shape a radio that you can build or buy.

In a software defined radio there are electronics and components to be sure, but the bulk of the work is done in the field of software and today I'm going to look at that.

Computers surround us, in our work place, in our home, on the street, in our hospitals, across our society. Each of these devices is running a thing called software, as opposed to hardware - a physical thing, software is intangible, in much the same way as your date of birth is intangible. You cannot hold your birth date in the air and point at it. You could write it down onto a piece of paper and point at the piece of paper that has the date on it, but you'd be pointing at a piece of paper, not your actual birth date.

Computers work in much the same way.

You cannot point at software, nor can you hold it in your hand. You can print it out onto paper, and point at that, but you'd end up with a deforestation problem that far exceeds the stripping of all the trees in the Amazon rain forest. To make matters more complex, there are at least two types of software, human readable and computer readable. You can translate human readable source code into a computer readable executable with a tool called a compiler, but doing it in the other direction is much harder.

Think of the ink on the paper that describes your date of birth. You can put the ink on the paper, but putting it back into the pen is more complex.

All this is leading somewhere, I promise.

A little while ago I started digging into how Software Defined Radios work and if you've been following along on my journey, there'll be parts that you can follow, parts that you sort of get, and bits that seem like black magic. This will be different for each person. My black magic is not going to be the same as yours and the things I understand without thinking might make your head explode. If that's not enough, the goal posts keep moving.

As I said, I started digging, much like peeling an onion, removing layer by layer, I've been exploring and learning and hopefully sharing my excitement along the way.

The other day a mate of mine came by with a new toy. A QRP or low power HF radio. The device itself is entirely driven by software, that is, it's a Software Defined Radio. It has some knobs and buttons, a display, a power socket, a plug for a microphone, an antenna, a speaker port and some other bits and pieces, but underneath all that is software.

What's special about this radio is that the software is Open Source, that is, you can peek inside and see what the code looks like before it becomes ink on the page, the human readable source code, rather than the computer readable executable.

I've touched on Open Source before and perhaps I should spend some time on that soon, but for now, think of it as a set of rules that dictate how you are allowed to use source code.

As any self-respecting IT geek, I went to the website where the software is available and downloaded it.

What struck me was that it was much simpler than I had expected. Don't get me wrong, this is a complex piece of software, not something I'm expecting to pick up in an hour or even a week, but it's simple as in digestible. I can point at different bits and understand what they do. This part does Morse Code, that does FM, over here is RTTY and look, over here is FreeDV.

If you're wondering, I'm describing the UHSDR, or Universal Ham Software Defined Radio project. Built originally by Chris M0NKA and Clint KA7OEI and sporting an impressive list of contributors, this software offers insight into receiving and transmitting using an SDR across a variety of amateur radio modes, including SSB, AM, FM, Synchronous AM, FreeDV, RTTY, CW as well as CAT or Computer Aided Transceiver, sometimes referred to as rig control or remote control, a way of using an external computer to control a radio.

The beauty of this software lies in its simplicity. Unlike many other projects, there is no code dealing with Windows, or with Mac OS, there is no mouse, touch screen, or other complex user interface. There is a limited set of buttons, a few dials and a screen for output. The end result is that the level of complexity is much lower than you'd find if you were to start digging into something like PowerSDR or some other code-base.

The point is that the UHSDR project is a really accessible way to start digging into the software behind a software defined radio and another path into this magical hobby of amateur radio.

I'm Onno VK6FLAB

This article is the transcript of the weekly 'Foundations of Amateur Radio' podcast, produced by Onno (VK6FLAB) Benschop who was licensed as radio amateur in Perth, Western Australia in 2010. For other episodes, visit http://vk6flab.com/. Feel free to get in touch directly via email: cq@vk6flab.com

If you'd like to join a weekly radio net for new and returning amateurs, check out the details at http://ftroop.vk6flab.com/, the net runs every week on Saturday, from 00:00 to 01:00 UTC on Echolink, IRLP, AllStar Link, Brandmeister and 2m FM via various repeaters, all are welcome.

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