About two years ago a friend handed me a small blue device that plugs into the USB port of a computer. As he handed it to me he said it would completely change the way I thought of radio.
I grew up in a household where radio was important. It enabled my immigrant parents, who had left western Europe for the Antipodes in the wake of the Second World War, to listen over shortwave to broadcasts from their home country.
As such, radio and antennas were commonplace to me, and I remember building crystal sets to pull in whatever signals I could. Eventually that led me to getting my amateur radio operator certificate in Canada.
However, as many can no doubt relate, along came a career, a family of my own, and other demands. The passion for radio ebbed, but always remained back of mind. A career heavily centred on internet technologies supplanted radio. After all, the internet was a sort of radio without the antennas.
As I neared retirement, two events reawakened my interest in radio signals. First was the gift of a small blue device made by a company called NooElec, and second was another gift, a small handheld transceiver made by a company called Baofeng. More about the latter in a subsequent column.
I was mystified by both. Clearly during my almost four-decade absence from amateur and shortwave radio there had been a major upheaval in the hobby, as I recognized neither name.
The parts for the blue NooElec device are fairly basic. First is the software-defined radio – actually a thumb drive or stick originally made for TV channel conversion in the UK following the move from analogue to digital transmission. Radio enthusiasts discovered that these sticks had amazing properties for tuning radio signals. The rest is history and these devices now sell for around $25.
The other part is an antenna. In my case, for the images you see above, I used an old set of TV rabbit ears.
My primary piece of software is called SDR#, pronounced “SDR sharp.” It is basically the software equivalent of a radio. The satellites I monitor broadcast around 137 MHz – a little beyond Rock 101 for instance, which broadcasts at 101.1 MHz.
There is additional software I use to keep track of the satellite and to start the tuner program when it is overhead. In addition there is software to turn the captured signal into an image, and yet more software to turn the rough image into what you see here.
Essentially my NooElec device is a radio on a chip, but not just any radio mind you. It’s not an FM radio. It’s not an aircraft band radio. It’s not a weather alert radio. It can be all of these, and more. Because it’s a radio defined by software, it can be multi-faceted – many radios in one if you will.
I can just as easily tune in a Vancouver FM station as I can the positioning signal from aircraft as far away as Oregon, or pull in an image transmission from the International Space Station as it passes overhead. (I can even pull in signals from neighbourhood backyard weather stations, but don’t tell anyone.)
Initially I could not grasp the capabilities of the sub-$30 device I held in my hands. After all, I thought, how could a device so small and so inexpensive take the place of the table-sized radios my father used in the 1960s.
Of course the answer lies in miniaturization and in the power of our modern computers. It all comes down to mathematics and being able to represent signals as waveforms that can be manipulated with software. Therein lies the secret to SDR, software-defined radios.
My experimentation with SDRs is really just beginning. I now have several units, some little bigger than a thumbnail. One is dedicated to aircraft position monitoring (my data is shared to an international consortium), another to ship tracking.
Two others are dedicated to weather satellite image data, capturing eight passes a day from both Russian and American meteorological satellites.
A fifth, more expensive, form of SDR, made by a company called SDRplay, is used mostly for so-called HF bands – high frequencies from 3 to 30 MHz , essentially taking the place of that shortwave set my father used to listen to Radio Nederland all those years ago.