A few years ago, people found out, that the MPEG decoder in the RTL2832 chip,
on which many TV dongles are based, can be bypassed, so that raw I/Q samples can
be pumped over the USB.
The fact that most tuner chips (like the R820T) used in these dongles can be tuned over a very wide frequency range, typically from 40MHz up to L band, made RTL2832 based dongles very popular among hams and other radio experimenters, despite their rather miserable dynamic range. For example, see this RTLSDR blog (external link)
So, I decided to give the dongles a try, too. Here are my results: