In my previous post about the virtues of microcontrollers in homebrew radio, I had a comment from Lee, who mentioned that he operated a LowFer beacon on 187khz. I’ve been passively interested in LF operation under Part 15 rules for a long time, but haven’t really gotten involved with it much. Lee operates from La Crescenta, about 375 miles south of here by my estimate. He made this little video documenting his setup:
If you are interested, you can check out the Long Wave Club of America website to learn more about Part 15 operation. If any of my readers have any other up-to-date or interesting LF/MF part 15 links, I’d love to see them added to the comments.
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.
Last year, Mark H (who blogs at Eastbay RC got me into the world of building RC airplanes. While my early attempts were limited in their overall successfulness (I demonstrated that I was awfully good at snapping props) I have been keeping up in my interest, and slowly acquiring more tools and hardware. Recently, I’ve had the opportunity to serve as a mentor to some local students and one of them expressed a desire to build his own RC airplane. I had recently been inspired by the great videos by Ed Orsine of the Experimental Airlines Youtube channel, so we decided that constructing an Axon, one of his designs would be a cool design to try:
A lot of it can be constructed with just Dollar tree foam and packing tape. But i recently got access to a 3D printer, and I thought it might be cool to fabricate some parts using that. A good candidate was the motor mount: we wanted the motor to be firmly held, with the appropriate 5 degrees of down angle. I just recently started teaching myself how to design simple parts using OpenSCAD. It bills itself as the “Programmer’s Solid 3D Cad Modeller”, and I couldn’t agree more: it plays right into my skillset. I’ve made an printed a few objects, and for these kind of purely functional 3D objects, I found it to be easy and straightforward.
The basic idea is to make a little plastic bracket that can be mounted at the end of a piece of 5/8″ square wood which is held with mounting tape inside the main fuselage. It took me about twenty minutes to design, and it went through a couple of minor tweaks before it got to it’s final form. And here it is, mounted in my student’s plane:
Mark H. thought it might be of interest to others in the builder/RC community, so I placed it up on thingiverse. Feel free to download it and print it, and let me know of you find it of value.
I find a lot of editorializing about amateur radio to be, well, curiously off the mark. For instance try checking out Dan, KB6NU’s well meaning article about why you should upgrade to a General. I mean, that’s what the title is: Why you should upgrade to a General. The reason I find this article so astounding is that despite the title, Dan doesn’t actually provide any reasons why you should upgrade to a General. The entire article presumes that whatever reasons you think you have for not upgrading, they aren’t valid. I find that a tiny bit presumptuous. But what’s really odd to me, is that there certainly are reasons to upgrade, he just didn’t bother to tell you any.
The most important difference (which underlies most of the others) is that you have access to spectrum which is unavailable to Technician class licensees. While Technician class licensees have all you can eat privileges above 50Mhz, they are pretty lean on the HF bands. With a General, you get full access to big hunks (but not all) of the spectrum below 6m, and this opens up a bunch of possibilities for communication. From SSB to RTTY to digital modes, you can participate more fully in the broad range of HF activity. The General exam is not a particularly difficult test, and you get a big bang for the buck. I’ve enjoyed WSPR, JT65 and beacon activity. And of course building and QRP operation. And just a lot of shortwave listening too (hey, no license required!)
But perhaps you don’t want to do any of that. Perhaps EMCOMM on VHF+ is your thing. Or maybe you like mountain-topping with 2m SSB. Or microwaves. Or APRS. Or D-Star. Or satellites. Or ATV. Or meteor scatter. Or EME. Or just hiking with an HT, or keeping in touch while on the road. I’m frankly okay with that, and I wish more hams were less concerned about what other people were doing, and simply got on with doing more of what they like in ham radio. Then, we wouldn’t have to scold and cajole people into upgrading: they would either be interested, or not. With the wide variety of interesting activity accessible to hams with Technician class licenses, it does not strain my credulity to think that it might be enough for someone.
When someone asks you why you don’t have your General or Extra class license, ask them how many moonbounce contacts they’ve made. If it is zero, urge them to upgrade their skills.
It is with a sense of deep sadness that I heard of the passing of Ray Harryhausen this morning. If I were to pick two things which influenced me as a kid growing up in the 1960s, it would have been the Apollo Space Program and the films of Ray Harryhausen, although at no time did I ever imagine that my own path would lead me toward a career in the film industry. What I found truly astounding about his work is that (perhaps by necessity) he excelled at all facets of his craft: from sculpting and character design, to animation and to the technical innovation necessary to make stop motion animation plausible in films. His work was always at the cutting edge of what was possible in special effects, and in spite of decades of progress they still remain vibrant films, important for their technical advances, but also because they are just fun to watch. Ray visited Pixar on several occasions, and while I didn’t get much personal time with him, I did get to thank him for his work and for helping to serve as inspiration, and he was kind enough to sign a copy of his book for me.
Pixar gave a nod to Harryhausen by naming a restaurant (curiously a sushi restaurant) after him in our 2001 film, Monsters, Inc. I doubt that there is anyone in the animation or visual effects industry who wouldn’t name Harryhausen as inspiration for what they do. So long Ray, and thanks for the films.
Even casual readers of this blog know that I’ve enjoyed playing around with the Arduino and the Atmel AVR chips. I really like them, and have used them for a variety of personal projects, as well as using them for a variety of educational projects for a local high school where I mentor students. But I also have a variety of other boards, from MSP430s to the BeagleBone, from the Raspberry Pi to the Parallax Propeller.
The truth is, I haven’t done a lot with the Propeller board. I must admit that a lot of it is simply inertia: if something you already know fairly well serves your needs, then learning something new is often a distraction from your task at hand. But there are things about the Propeller that I do find interesting and compelling.
It’s fast. The chip can be clocked up to 80Mhz, and has 8 cogs, each a 32 bit core with 2KB of local storage for instructions and data.
It has a built in byte code interpreter for SPIN, a high level language. Each cog can execute about 80,000 of these high level byte codes per second, or about 640,000 max if all cogs are funning. I have mixed feelings about Spin, but it’s a cool idea nonetheless.
It avoids interrupts, preferring to use cogs to process events. Interrupt processing is challenging for new programmers (and in some cases, even experienced ones) and the cog model might be easier and more flexible for many real time tasks.
It avoids dedicated hardware peripherals, instead providing “virtual” peripherals as software. Because the chip is fast, and there are many cogs, it’s possible to implement many devices such as UARTS, PWM, servo drivers and even video as code which runs on a particular cog in parallel with the user program. This gives the programmer a great deal of flexibility. SPIN supports a library of user-contributed objects which can really lend to the flexibility of the Propeller.
So, there is lots to like! So, for the second year in a row, I’ve shuffled off to meet some of my friends from tymkrs.com at the Official Propeller Conference. It’s a fairly small get together of Propeller enthusiasts, hosted by Parallax and featuring short presentations on Propeller hardware and software techniques. I had a lot of fun. Parallax is a remarkably small company, run by Ken and Chip Gracey, and having maybe forty employees. Besides the Propeller, they manufacture a bunch of other items, including sensors and robotics items. The highlight of the day was a talk by Chip about the upcoming Propeller 2. Chip’s talk was remarkably informative, and so devoid of normal marketing bull that I actually blinked several times at his honesty.
Propeller 2 looks very cool. To me, the most exciting thing is that it one ups the flexibility of the Prop 1 in allowing any pin to be configured as digital or analog, and an input or output. The Prop 1 has been used by hams to directly generate beacon signals but the new capabilities would seem to open a variety of demodulation as well as modulation techniques. Chip said that the first actual silicon for the Prop 2 will be arriving at Parallax this Monday, and that he’ll let us know via the Parallax forums how that goes. I’ll be paying attention.
I had a great time, culminating with a BBQ dinner with Atdiy, Whisker, Roy, Joe, and some of the Parallax crew. It’s inspired me to actually dig in and start learning Spin. I’m staring over at my Parallax board, happily blinking LEDS. It’s a start.