SDR - Software-Defined-Radio
If you listen to our daily net you've heard our members referencing the "SDR". You might be wondering what that acronym stands for. Well, you've come to the right place! This page contains a brief explanation of the term SDR, why it is useful to radio operators in general, and how we use it to make the net more fun and more efficient. Following the narrative will be a list of links to SDR sites that are major players for our members.
You are presumably familiar with a radio and have a general idea of how it works. The typical radio contains a bunch of components (ICs, transistors, diodes, etc.) that detects signals, filters them, splits them into a carrier (which is discarded) and content (which is processed further.) The content is further filtered, augmented, enhanced and amplified to produce an audible signal. (We are limiting this discussion to radio traffic that contains voice content otherwise known as phone operations in the ham world.) In order to modify how the radio works or add some new functionality, you'll need a soldering iron and more components, not to mention the know-how, to make it happen. Or you could buy a new radio.
The software-defined radio (SDR) is a combination of a little bit of hardware with a computer and some very nifty software. The hardware handles most of the RF tasks while the software, running on a common computer, does everything else. Attach an antenna to the SDR, plug it into a computer, fire up the software and we have a full-featured radio receiver! (There are SDRs that function as transceivers, but we're limiting this discussion to SDR receivers.) The beauty of this hybrid system is the flexibility provided by the software. Want to add DSP? Do it with software! No need to buy any more hardware. Want to share the radio with friends? Again, software (and the internet) can make that happen.
The SDRs referred to by our members are setup as shared resources on servers connected to the internet. All anyone needs to use them is a browser and a URL. Navigate to the site and you are in control of your own SDR instance. You can tune to whatever frequency you like, set a squelch threshold, adjust the volume, etc. In short, you can control the radio as if it was sitting there in the room with you!
The links shown below are SDR sites located in widely-dispersed areas of the country. Take some time to try them out! You'll find it very helpful to receive signals that are not reaching your own antenna!