Gqrx is a software defined radio receiver powered by the 
GNU Radio SDR framework and the Qt graphical toolkit.
Gqrx supports many of the SDR hardware available, 
including Funcube Dongles, rtl-sdr, HackRF and USRP devices. 

Gqrx has the following features:

Discover devices attached to the computer.
Process I/Q data from the supported devices.
Change frequency, gain and apply various corrections (frequency, I/Q balance).
AM, SSB, FM-N and FM-W (mono and stereo) demodulators.
Special FM mode for NOAA APT.
Variable band pass filter.
AGC, squelch and noise blankers.
FFT plot and waterfall.
Record and playback audio to / from WAV file.
Spectrum analyzer mode where all signal processing is disabled.

NOTE: 
To successfully run gqrx you must build gr-osmosdr with 
support to your hardware (eg rtl-sdr,uhd) and have installed 
on your system the latest version of libusb (1.0.19)
(you can grab it from slackware current)

NOTE:
If you use a DVB-T dongle keep in mind newer kernels already 
contains a DVB driver, however, we do not want to use this. 
The above "modprobe -r dvb_usb_rtl28xxu" command unloads this 
from the kernel, however for a permanent solution you will 
need to create the following file in /etc/modprobe.d/:
rtl.conf and add this line: blacklist dvb_usb_rtl28xxu