Earlier this year I discovered (maybe re-discovered) websdr.org, a site that hosts many online SDRs, or “software defined radios”, that allow you to stream radio from nearly anywhere. Perhaps streaming is the wrong word…
Software defined radios are an interesting concept to grasp; while on the surface it seems that they’re simply a radio receiver hooked up to a computer and piping audio through, they’re actually more than just that. The computer isn’t receiving audio, it’s actually receiving a digitized version of all the electrical signals the antenna is receiving, or at least a chunk of them. The size of the “chunk”, or the “bandwidth” you can see at once depends on the SDR and the performance of the computer. The computer is literally processing the signals the same way all the electronics in the radio normally does, pass it through some serious math processing (waaaay over my head), and actually turn it back into not only audio, but a portion of the band, not just one station!
What this means is that whereas normally you would record audio from a radio, from a single station, an SDR would let you record a chunk of the actual radio signals being received, and you can literally play back those signals and actually browse around to any stations received within that bandwidth. For example you could record the lower portion of the 40 meter band during a CW contest, and literally browse around listening to all the various conversations taking place later on. In addition, having that bandwidth means having a “waterfall display” to literally see and click on stations to tune in.
SDRs come in all shapes, sizes, and prices, with the “RTL-SDR” being likely the lowest-cost SDR you can get (sub $25 range!!), and no maximum limit, with something like a Flex SDR transceiver being an example of a “cadillac” transceiver, with an SDRplay receiver being a nice middle ground at around $120ish price point. On the computer side you can use something a simple as a Raspberry Pi, a decent Windows tablet, or a high-end gaming PC to process the data from the SDRs. There are a number of SDR software packages out there; some are hardware-dependent and others work with nearly anything.
That said, one interesting thing you can do with an SDR is to use some software called WEBSDR to put your SDR on the web, and let others listen in on it. While it’s not the only software package that does this, it works fairly well and the web site lists many online web sdrs that you can tune around on with nothing more than a browser. I recently discovered the websdr sites even work on Apple (IOS) and Android mobile devices, so you can use you iphone, ipad, or Chromebook tablet to listen around the world. This is great for those (like me) that are antenna-limited or apartment dwellers.
Being able to use a mobile device with websdrs is a game-changer; it means band conditions may not matter anymore if you can simply choose to tune into a websdr in another country. It means needing nothing more than the phone in your pocket to “play radio” on your lunch hour, at least for listening anyway.
I get it and I tend to be “old school” when it comes to ham radio stuff; I like messing with the real thing with knobs and buttons and all, but having simple access to tune means learning more about digital modes and CW and playing with FLDIGI when just listening, as opposed to fiddling with antennas and wires when there’s a foot of snow outside.
Have fun – and while it’s cool to listen – get licensed and get on the air!