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Why You Should Care About Software Defined Radio

It has not yet become a household term, but software-defined radio (SDR) is a major player on the cutting-edge front. Whether you’re creating consumer products or just playing for fun, SDR is worth knowing and I’ll prove it to you.

SDR comes down to a difficult problem

First, let’s reconcile what is meant by “radio.” If it sends or receives on a radio frequency, it has a radio. This means that your WiFi router, your mobile phone, your laptop, many water meters and electrical meters, the garage door opener (but not the TV remote that uses light), the wireless security sensors, the police radios, your wireless mouse / keyboard and this quadcopter keep bumping into the neighbor’s yard everyone has one. Radio stations are so prolific that we are tempted to tell you that they are in everything.

Ettus Research USRP N210

The radio was much harder. On the communication side, you can buy an expensive radio and / or transmitter that requires the use of an experienced operator. At a lower level, you would like to choose a specific tape and deal with things like a modulator, mixer and filter, along with many barriers to production that would also lock you into a specific application.

Software-defined radio solves some of these problems by allowing you to control how the radio’s hardware works based on software. This was also exacerbated by the availability of low-cost, large-scale hardware. This is not the end of the radio, but it makes the problem easier. This has led to wider acceptance, but we believe that what we have seen so far is just the tip of the iceberg.

Here you can see the USRP N210, which is a professional tool used by hardware developers who work with RF in their products. This tool proved so popular that National Instruments bought designer Ettus Research and now includes USRP with its LabVIEW systems. The USRP-210 mid-range model is a very capable SDR operating from DC to 6 GHz.

You can change it once it is built

Florian Fuchs / Wikipedia / CC-BY-SA 3.0 [CC BY-SA 3.0 (], via Wikimedia Commons
Florian Fuchs CC-BY-SA 3.0 via Wikimedia Commons

The whole point of SDR is the lesser need for specialized hardware. One module can address a wide range of applications, even those that are currently unknown. Building and sending hardware has high overhead costs, but formulating and distributing software (or firmware) updates can have much lower associated costs. Devices communicating via SDR do not lock a platform in a specific set of communications. For example, if you sell a base unit and multiple remote devices, switching the communication method to version 2 may make older hardware useless. You will have satisfied customers if they can continue to use their old accessories after a simple upgrade. It is quite possible that such improvements are pushed through the air (as from a base unit), as seen in many smartphones.

Of course, the multiplier is a development created by crowdsourcing. A prediction for the future is a connected world. If the device’s firmware is released as Open Source, a motivated community will find a way to make that hardware even more useful.

In the next section I will talk about the DVB-T switch, which can be seen here. But one important thing to understand is that the chip inside this device is an SDR and is already being used commercially. The versatility of the chipset inside proves that SDR is a viable choice in consumer hardware. I would like to see reliable figures on how many of them are sold for TV viewing, compared to SDRs. It’s great for companies that throw them away anyway.

Start studying for a few dollars

Don’t be ashamed if you know nothing about all this. That’s where most people are, and you don’t have to spend a lot of money or know much to do SDRs. Let’s face it, wireless communication is as close as the pragmatic mind is going to call something “magic,” and that makes SDR a pleasure.

Start Simple

What really turned my head was the appearance of what is known as RTL-SDR. It is the practice to use USB keys for a TV tuner for software-defined radio. That’s right, these “DVB sticks” are made for watching TV on a computer, but inside is a Realtek 2832U.

SatNogs satellite receiver is based on DVB-T Dongle and SDR

Connecting the key to the computer and launching some software allows you to listen – both audio signals and transmitted data – to all sorts of things. We read with pleasure [Dr. Droopy Nayhey’s] SDR Guide because it goes along this route. $ 12 in hardware (plus the computer and cables to be honest) and it tracks planes, listens to the emergency tape, FM radio and “treasure hunt” for all the things in our world that are broadcast.

Don’t be afraid of this, these are just receivers, so you don’t need a license or pre-training. We have seen these changes automated aircraft imaging equipment and eventually you can add to the FlightAware flight tracking data network. Even the winners of the 2014 Hakkai Prize Grand Prix build a satellite receiver around a DVB switch!! Do you see this little black stick centered vertically? Satellites transmit information back to earth, you just have to listen to the data.

For starters and well-targeted applications, these switches are a good option. But they are limited from about 22MhZ to 2200Mhz depending on the specific key you have. Going beyond these limits requires jumping to different hardware.

More serious

Parts that make up PortableSDR
Parts that make up PortableSDR

I said earlier that the SPT solves some problems, but certainly not all. One device cannot control all RF communications (yet). So those who get a little more serious look at specially designed SDRs than the support of these TVs. This is still better in many ways than the former radio equipment, as these boards boast a very flexible set of features.

Here we see an interesting idea about SDR, which took third place in the 2014 Hackaday Award. PortableSDR eliminates the need for a computer to manage the software side of things and puts the circuit in a durable case with a special display as part of the user interface. It is aimed at people who are becoming more serious in the field of radio amateurs, but it is still a tool only for acceptance.

On Monday we made an appeal to complete the story of Cinderella for the Kickstarter portable SDK. I still hope that this one will succeed, because I believe it is part of the modernization of the amateur radio movement.

Another example of this rebirth is SDR equipment specifically designed for radio amateurs. We watched such a construction as it progresses. This concentrates around a Softrock SDR board which is controlled by Teensy 3.1 and again, has a special user interface that does not require a computer. Do you notice the convergence here between traditional amateur radio skills and the hacker movement?


Do I have to say more? There is a growing movement of people playing with SDRs. This will lead to interesting new applications and I believe that it will ultimately stimulate consumer electronic design. But if you need more inspiration, just take a look the kinds of things that people build around SDRs and make your own predictions.

[Featured image source:]

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