An FM receiver is the first thing in every GRC tutorial. I just wish there was something useful that one can receive with one of these standard $15 RTL-SDR receivers that isn't super complicated or FM radio.
There are all sorts of interesting and useful things you can do with them: monitor/troubleshoot various AM devices around the house (weather stations, garage door openers etc), tune in to a number of amateur radio bands (there's surprising amount of traffic on them), receive NOAA weather broadcasts, aircraft broadcasts, debug DIY projects (433MHz transmitters etc.)... there's a lot of stuff being broadcast in the frequencies that these dongles can receive. You just need a decent antenna[1] and to explore the spectrum around you a bit.
Granted, the absolute most common cases are out of reach with the cheap dongles due to frequency, bandwidth and encryption issues (i.e. ATSC, Wifi, Bluetooth) So they're not going to be terribly interesting to the average consumer but they are very handy little devices for hackers with any interest in RF.
[1] The default antennas they ship are not useful over a wide range of frequencies and/or for weak signals
The 433Mhz band is quite interesting - key fobs, garage door openers, and other cheap and cheerful "wireless" technologies often work on this band. Part of the fun is finding out what! Tune your SDR and go hunting...
In a city house with many apartments there's a lot that can be received, produced either by you or by neighbors.
But you have to be interested in the topics, find the right tools to decode what you're interested etc.
As an example: with not too much effort I've been able to listen and read a number of the temperature sensors around sending their readings. Then if you collect them for some period of time, you can try to analyze and process them to figure out how much of "noise" they collected (as if when they are mounted outside of a window and the window is open during the winter) versus the real signal (the outside temperature), and how many are completely broken etc, all based only on the data (e.g. when not seeing all the devices you record and when not knowing their placement).
It is fun for somebody who is interested in such kind of experiments (but not everybody considers such experimentation fun -- and then no tutorial is enough).
We live in the times where there are still unencrypted signals around. in some future, maybe there won't be anything to listen that would mean anything without the keys -- everything will be just encrypted noise.
Oh, that's right! I forgot about that. I think some friends did once and it wasn't as easy to receive as something like FM, but on the roof of a tall building I think it worked okay. Thanks for reminding me to try that!
I was able to read my neighborhoods unencrypted power meter data within an hour of receiving my first rtlsdr. I also live under a flight path and found it pretty fun to listen to the pilots overhead obtain their landing clearances. Building a dish and downloading satellite images from NOAA or GOES also looks fun.
