[GLLUG] software defined radio in Linux

[Charles Ulrich]

So, software-defined radio (SDR) is basically doing radio signal 
processing in software rather than in dedicated hardware. (Your car 
stereo is an example of a dedicated hardware radio.) Consumer-level 
computers are now fast enough these days that they can do the rather 
complicated radio signal processing in software and in real time. This 
beings a host of benefits to the state of the art in radio. (But don't 
ask me to explain them because I'm not sure I'd be able to make much 
sense. :)

Unfortunately, SDR transceivers (the stuff between the antenna and 
computer) have been somewhat expensive because they're pretty 
specialized and are not exactly mass produced. Last time I went looking, 
the most popular one was well over $600. However, someone recently 
discovered that there are some cheap (around $20) USB television 
receiver dongles which turn out to also be pretty decent, if limited, 
SDR receivers.

I ordered one of these from Amazon and got around to trying it out over 
the past few days. It covers most of the VHF and UHF bands. (Though I've 
heard of people getting wider coverage with homebrew frequency converter 
thingies.) Using a program called "Gqrx", I've been able to tune into 
weather radio, FM radio, air traffic control, and police dispatch from 
the comfort of my desk at home. The downside is that this stuff is so 
new, you can't just apt-get or yum your way into a working setup yet. 
Compiling GNU Radio and other dependencies is nontrivial. I didn't 
follow a howto since my distro is old, but there are some out there.

I'm planning to attend this week's meeting to share what I've managed 
so far. I'm just dipping my toes in so to speak, so I probably can't 
answer all questions. Google "RTLSDR" to see what the Internets are 
saying about all this.

Charles