I have an R820T DVB dongle and the rtl_sdr software on a linux computer.
I can listen to various frequencies using the gqrx software which uses the rtl_sdr library as a device driver for the USB-attached dongle. I also (obviously) get the spectrum scope and waterfall display of adjacent channels. Thus, the hardware and software is functional at some level.
Now I notice there is a separate program in the rtl_sdr bundle also called "rtl_sdr" that can record a slice of spectrum onto the hard drive.
Here is an excerpt from the usage reminder generated by running rtl_sdr with no parameters:
rtl_sdr, an I/Q recorder for RTL2832 based DVB-T receivers Usage: -f frequency_to_tune_to [Hz] [-s samplerate (default: 2048000 Hz)] [-d device_index (default: 0)] [-g gain (default: 0 for auto)] [-p ppm_error (default: 0)] [-b output_block_size (default: 16 * 16384)] [-n number of samples to read (default: 0, infinite)] [-S force sync output (default: async)] filename (a '-' dumps samples to stdout)
For a test, I wanted a loud continuous narrow band FM voice signal, so I attempted to record the local national weather service transmitter on 162.55 Mhz with
rtl_sdr -f 162550000 -g35 -s 1000000 test1.dat
I note that this also records the 1 Mhz sample around 162.55 Mhz. Large files are made quickly. A few minutes netted about 300 MB. I've noticed he R820T is finicky and won't always set low sample rates, and once again this is only to produce a test file. If I wanted to leave it run all night on some other frequency range, I would consider finding a smaller sample rate.
Once recorded, what program plays these files? Although gqrx has an option to play an I/Q sample file, it doesn't seem to play files made with rtl_sdr. I get a blank waterfall and no audio when attempting to play the file in gqrx.