brainwagon

As anyone who has followed my blog for any period of time knows, my interests straddle a lot of different disciplines and hobbies, and often find interesting bits of overlap where I find I can do cool stuff. Two of my favorite hobbies are tinkering with microcontrollers and with the low powered end of amateur radio, what we call “QRP radio”. A few of my previous projects (mostly related to beacons and sending automated Morse signals) have been in the overlap.

In the recent SolderSmoke Podcast #152, Bill, N2CQR recently took a tiny step into that overlap himself. He got himself Arduino, probably the most popular microcontroller platform, and used it to send out Morse, and then control an inexpensive DDS module to serve as a cool little VFO, complete with a rotary encoder to tune and a little LCD module to give the readout. Check it out:

Pretty darned cool. And both economical and useful. Bill was pretty sheepish about this tiny step into the digital world. In the past, he has expressed a greater comfort with radio circuits that are built from discrete components, such as diode mixers constructed with trifilar coils rather than the NE602 integrated circuits. After building radios with just a handful of discrete transistors, using even the simplest microcontroller which has tens of thousands (if not more) can seem like crass extravagance.

But I think he should cut himself some slack. Actually, not just cut himself some slack, but revel in the new direction his hobby has taken him.

In the strictest sense, QRP radio is just any communication which takes place with less than 5 watts of radiated power. But in the broader, more ideological sense, it means constructing radios which are simple, inexpensive and well optimized, without a surplus of useless features of whistles. There is a certain economy of design. When you look at VK3YE’s design for his “Beach 40” DSB rig, you have to marvel at the coolness of the design. Only 8 transistors, nicely documented in his videos. He draws the entire schematic out from memory while on the beach.

If your aesthetic finds this kind of circuit pleasing, the idea of injecting a microcontroller into the mix may seem like drawing telephone wires in the background of the Mona Lisa. But I’d submit that you can find aesthetic uses for microcontrollers in radios, even while being able to appreciate these great discrete, analog designs.

First of all, microcontrollers enable new and useful features. Even the simplest microcontroller can be used to send automated signals for things like QRSS beacons. Hans Summers super low power QRSS beacon can send a nice “shark fin” signal using only three transistors, but if you want to send your callsign, it rapidly becomes more difficult. Sure, you could strap a laptop or desktop computer to generate the modulating signal, but that seems very unaesthetic: hundreds of dollars and tens of watts of compute power just to drive a $5 transmitter with only a few milliwatts of output power? He actually sells a little preprogrammed microcontroller that will do the work, or you could get a K1EL keyer chip, but you are injecting a black box in your design, without any understanding or modifiability. But you could open that box up yourself. For the price of a pizza, you can get a dev board that will hook up to your laptop for programming, pull a few milliwatts of power, and dutifully key your transmitter. Once you get familiar with that kind of work, you can then make an embedded controller using just the raw chips: for instance, I have a few of these Atmel ATTINY85s that I got for $1.15 each (about the same as a 555 timer from our local Radio Shack) lying around for such applications. Add a crystal and two caps (or maybe even do away with the crystal, and use its internal oscillator) and your beacon becomes more flexible and more useful. Want to change the message? Have it send the current temperature or battery voltage as well? Piece of cake.

Second, microcontrollers are the easiest step into understanding computers. When I got my first computer back in 1980, it was already pretty difficult to understand the innermost workings of computers, although I did fairly master most aspects of my Atari 400. With modern desktops or laptops, it seems basically impossible. They have dozens of subsystems, with all sorts of interface and operating systems complexity. But these microcontrollers don’t have any operating systems, and because they are mostly self-contained, the total amount of stuff you have to learn is relatively limited. You tell the microcontroller to flip a voltage from low to high, and it does it, without drivers or intermediate layers. It allows the same kind visceral understanding and exploration that QRP is meant to stimulate.

Thirdly, just like the QRP community, it allows you to participate in a robust, vibrant community of experimenters. The people who are experimenting with Arduinos are kindred spirits to the homebrew radio enthusiasts. They want to take simple, cheap building blocks, and through the power of their understanding construct new, useful and novel applications. Even when their area of interests may differ from ours, you can learn from their skills and draw inspiration from their enthusiasm. And we might even find some potential hams in their ranks.

Don’t feel bad Bill: embrace your new digital skills. The more you goof around, the more applications you’ll find, and the more empowered you’ll be. Computers and QRP can co-exist, and even enhance each other.