sdr (software defined radio) is an emerging technology that sprang from the increasing power of modern computers catching up with the efficiency of old school (mostly analog) electronics. when this happened, computers attained the power to do all the cool stuff that an am/fm/ham/etc radio receiver can do but without all the expensive specialized hardware. this lowered the investment cost for casual tinkerers and hardcore engineers alike.
software defined radio was born quite some time ago but only became popular recently when it was made popular that ~20$ wireless HDTV usb receivers could be used as a cheap instrument to tap into all kinds of RF (radio frequency) signals. while these usb devices were sometimes limited in some ways, they provided the masses with the ability to glimpse into a very niche technology that was not commonly known even among technically minded individuals. this popularized an otherwise unknown niche and brought in fresh minds to an otherwise stagnant closed off community, leading to many cool new SDR related devices being prototyped and sold.
something i often pondered myself is, "how cool would it be if all the people running these sdr devices on their networks were to get together and create a massive worldwide sdr listening portal." if you think that's a cool idea too then look no further than websdr.org, a website that does exactly what i wrote above. it's an index of listening stations all around the globe that lets you tune in (in real-time!) to some anonymous donors sdr device, along with often hundreds of other people. you can scan channels and configure bandwidth and decoding options to your hearts content! you see, sdr works a little differently than your home radio, you don't have to pick one channel at a time, as the listening device often just dumps out all the channels it can hear in a give range. this allows any number of people to tune in to different channels at the same time with no penalty. cool, right?
- pick a location to listen from (there is a world map at the bottom of the main page) note the number on the map, scroll back up to the link provided at that number and visit the site that's linked. for this example we'll be using the #1 station.
- you should now see a radio-like interface. the different color bar (called a waterfall) that extends across the screen horizontally is how you will select a station. find a whitish line on the waterfall analyses and click on the yellow arrow below to tune to that station.
- now select from: [ cw / lsb / usb / am / fm ] to set the transmission type you want to decode, typically stations i've found are in AM but they could be any of the options so go through them all.
- back up on the waterfall you should see two diagonal ( / \ ) lines next to the straight line ( | ). drag these together to tightly encompass the signal you are listening in to in order to get a cleaner signal.
- now that you've successfully acquired your first radio signal, play around with the other options on the page to clean up the transmission or find others using this same method.
- have fun and continue to revel in and enjoy the wondrous world of internet sdr!