It hasn’t become a household term yet, but Software-Defined Radio (SDR) is a major player on the developing technology front. Whether you’re building products for mass consumption, or just playing around for fun, SDR is worth knowing something about and I’ll prove it to you.
SDR Boils Down a Hard Problem
First off let’s reconcile what is meant by “radio”. If it sends or receives via radio frequency it has a radio in it. This means your WiFi router, your cellphone, your laptop, many water and electrical meters, your garage door opener (but not your TV remote, that uses light), wireless security system sensors, police radios, your wireless mouse/keyboard, and that quadcopter you keep crashing in the neighbor’s yard all have one. Radios are so prolific we’re tempted to tell you they’re in absolutely everything.
Radio used to be a lot harder. On the communications side of things you could buy an expensive radio receiver and/or transmitter that required a skilled operator to use. At a lower level, you would be looking at choosing a specific band and dealing with things like modulator, mixer, and filter design, along with plenty of roadblocks to manufacturing which would also lock you into a specific application.
Software-Defined Radio solves some of these problems by allowing you to control how the radio hardware functions based on software. The advent of this has also been boosted by the availability of inexpensive hardware produced at scale. It is not the end-all of radio, but it makes the problem easier. That has led to wider adoption but we think what has been seen so far is only the tip of the iceberg.
Seen here is the USRP N210 which is a professional tool used by hardware developers that work with RF in their products. This tool proved to be so popular that National Instruments bought designer Ettus Research and now incorporate the USRP with their LabVIEW systems. The midrange USRP-210 model is a very capable SDR, operating DC to 6 GHz.
You Can Change It After It’s Built
The whole point of SDR is less need for specialized hardware. One module can address a wide range of uses, even those that are currently unknown. Building and shipping hardware has high overhead, but formulating and distributing software (or firmware) updates may have much lower associated costs. Devices communicating using SDR don’t lock a platform into one specific set of communications. For instance, if you sell a base unit and multiple remote units, switching up the communications method in version 2 could render older hardware useless. You will have happy customers if they can can continue using their old accessories after a simple upgrade. It’s entirely conceivable that such upgrades would be pushed over the air (like from a base unit) as is seen with many smartphones.
The multiplier is, of course, crowd-sourcing development. One forecast of the future is a connected world. If device firmware has been released as Open Source, a motivated community will find a way to make that hardware even more useful.
In the next section I’m going to talk about the DVB-T dongle seen here. But one important thing to realize about it is that the chip inside this device is an SDR and is already in use commercially. The versatility of the chipset inside proves the point that SDR is a viable choice in consumer hardware. I’d love to see reliable numbers on how many of these have been sold to watch television, versus to tinker with SDR. Either way it’s great for the companies churning them out.
Start Learning for a Few Dollars
Don’t be ashamed if you know next-to-nothing about all of this. That’s where most people stand, and you don’t have to spend big or know much to dabble in SDR. Let’s face it, wireless communication is as close as a pragmatic mind will get to calling something “magic” and that makes SDR a delight.
The thing that really turned my head was the advent of what is known as RTL-SDR. This is the practice of using television tuner USB dongles for Software-Defined Radio. That’s right, these “DVB Sticks” are made to watch broadcast television on a computer but inside is a Realtek 2832U.
Connecting the dongle to your computer and launching some software allows you to listen in — both audible signals and transmitted data — on all kinds of things. We’re enjoyed reading [Dr. Droopy Nayhey’s] SDR guide on Hackaday.io because he’s taking this route. $12 in hardware (plus the computer and cables to be fair) and he’s tracking aircraft, listening to emergency band, FM radio, and “treasure hunting” for all the things in our world that are transmitting.
Don’t be afraid of this, these are receivers-only so you need no license or prior training. We’ve seen these morph into automated airplane filming rigs and you could end up adding to the flight tracking data network of FlightAware. The Grand Prize winners of the 2014 Hackaday Prize even built a satellite receiving station around a DVB dongle! See that little black stick centered vertically? Satellites do transmit information back to earth, you just need to listen for the data.
For getting started, and well-targetted applications, these dongles are a good option. But they are limited from around 22MhZ to 2200Mhz depending on which particular dongle you have. Going beyond those limits requires a jump to different hardware.
Getting More Serious
Earlier I said that SDR solves some problems but certainly not all. One device can’t rule all RF communications (yet). So those getting a bit more serious look to purpose-built SDR rather than piggy-backing on those TV receivers. This is still better in many ways than radio equipment of yore, as these boards boasts a highly versatile set of features.
Here we see an interesting take on SDR which placed 3rd in the 2014 Hackaday Prize. PortableSDR does away with the need for a computer to drive the software side of things and puts the circuitry in a durable case with a dedicated display as part of the user interface. It is aimed at people who are getting more serious about amateur radio, but as it stands is still a receive-only instrument.
On Monday we made an appeal for a Cinderella-story finish for the PortableSDR Kickstarter. I’m still hoping that this one makes it as I do believe it’s part of the modernization of the amateur radio movement.
Another example of that rebirth is SDR equipment specifically designed for amateur radio operators. We’ve been watching one such build as it progresses. This one centers around a Softrock SDR board which is controlled by a Teensy 3.1 and again, has a dedicated user interface that requires no computer. Notice the convergence here between traditional ham radio skills and the hacker movement?
Need I say more? There’s a growing movement of people who are playing with SDR. That will lead to interesting new applications and I believe it will eventually drive consumer electronic design. But if you need more inspiration, just look at the kinds of things people are building around SDR and make your own predictions.
[Featured image source: HDSDR.de]