A cheap solution for Software Defined Radio (SDR)

A software-defined radio system, is a radio system where components are implemented in software instead of special hardware. A recent post in the slashdot about an implementation of this system using very cheap DVB-T/DAB receivers. Following up the links, i discovered the reason behind this: the RTL2832U chip. Searching a bit more i got a list of supported hardware. Searching in local shops i bought a Lifeview LV5T Deluxe usb receiver and i started to play (~20 euro).

First of all, i had to install a different usb driver from the default. After that you have to download and install the HDSDR program. Finally, you have to install a plugin at the top of HDSDR to control the receiver. First experiences seems promising: receiving local radios and local tv stations. The HDSDR application supports FM demodulation, so i was able to hear (with some modifications in the sample rate etc) local radio. Unfortunately, the receiver does not support lower frequency band less than 64 MHz. Moreover, the quality of the software demodulation was low, and the sound includes a great amount of noise, although you can understand the conversations. I 'm not sure about the source of the low quality results, but i had to play with the sample rate of the us device (for the radio i used 0.90001 MS/s with 96000 output sample rate) and for exploring the frequency band over 300MHz, 3.1MS/s.

Here is an example screenshot running the HDSDR and searching the band around 88 MHz:

HDSDR receiving 86.4 MHz. Note that the signal is an artifact as explained in comments.

Notice the three radio stations on the right (FM modulation) at 88, 88.4, and 88.7 MHz. The station at 88.4 MHz has the lower signal. Moreover, in the left screen we can see a very strong signal at 86.4 MHz which is out of the typical FM spectrum and the modulation does not seem to be FM. The reception was done using a very small antenna included in the usb receiver from the ground floor. Tomorrow, i'm planning to use an old TV antenna (not very good for the FM band.. but i think it will be ok for my tests) and start exploring the different bands :).