Version 2.6 of the popular SDR program GQRX has just been released (changelog). GQRX is a general signal browsing program similar to programs like SDR#, HDSDR and SDR-Console. However GQRX is designed to run on Linux, MacOS and Raspberry Pi 2 & 3. Note that v2.6 is still a work in progress for MacOS. Apart from the new features and bug fixes, one of the major improvements appears to be reduced CPU usage, meaning that it should run better on older PCs. The changelog is pasted below:
1-2-5 scaling on FFT axis.
Remember AGC settings between sessions.
Right-click on FFT resets frequency zoom.
Separate dB ranges for pandapter and waterfall.
Raw I/Q mode.
Command line option to set Qt style (fusion, windows, …)
Binary packages for Raspberry Pi 2 and 3 (see below)
Stuttering audio with Pulseaudio backend.
Use system font on FFT plot (too small font on high res displays).
Broken FUNcube Dongle Pro+ support on Mac OS X 10.11.4.
Correct display of negative offsets between -1 and 0 kHz.
Reset frequency digits below the one that is being changed.
LNB LO could not be set from I/O configuration dialog.
Update squelch level when switching between demodulators.
Set correct filter range when loading bookmark.
White area on waterfall.
RFSpace Cloud-IQ support on Mac OS X, RPI binaries and in PPA.
Input decimator performance.
SDRPlay integration through SoapySDR.
Only probe for devices when the program is started.
Recently we found this excellent quick start guide by Kenn Ranous which shows how to set up various RTL-SDR related software programs on (Debian) Linux. The guide shows how to install the drivers, how to install and set up GQRX, CubicSDR, dump1090, Virtual Radar Server, QSpectrum Analyzer and SDR Trunk.
If you are struggling with getting an RTL-SDR to work on a Linux system then this should be a very good starting point.
The thing I like most is that I can replay past transmissions by clicking in the waterfall history. Using other SDR software, when a new transmission pops up, I feel like I’m in a race to tune to it before it ends so that I can at least hear some of it, but in my software, I don’t even have to pay attention to what’s happening now, and so I seldom do. Usually I don’t notice transmissions on new frequencies until they’ve ended, but I still get to listen to them.
I also put some effort into trying to make sure AM and FM transmissions were equal in volume, as well as at the correct volume according to how well they were modulated, in that I aimed for 100% modulation leading to audio output that’s 6 dB below the ceiling. It seemed as if it was quite random in other software, as switching from AM to FM might cause a huge jump or drop in audio volume. I don’t like to play with my volume controls, so I did my best to make it so that I don’t have to. I’m also not at all fond of the “click the numbers” method of changing the center frequency which seems to be so common. So in mine, I just type in the MHz on the number keypad and press enter.
I’m also much more fond of my waterfall coloring scheme than any other I’ve seen. It seems much smoother and more informative, at least to me anyway. I suppose that’s rather subjective.
…but it’s rather hard to compare it to other software given that I only got to use other software for two or three days. I rather soon knew I wanted to write my own, and I wanted to use the V4L2 API (that dvb_usb_rtl28xxu module you have to blacklist to use rtl-sdr is an SDR driver, not a video driver), but I had to upgrade to Linux Mint 18 to get access to it since it’s a new API, and after doing so, I haven’t been able to get any of the existing SDR software to both compile and work after it’s compiled. So I just focused on writing my own, since I was wanting to do so anyway. (No support for that V4L2 API though, as it turns out its buggy and offers no way to control the dongle’s gain, so it’s basically unusable.)
In this episode of Hak5, a popular YouTube technology channel, Shannon shows how to use the RTL-SDR on Debian Linux. She shows how to install the RTL-SDR drivers from scratch if using a distribution without them pre-installed and also shows how to install and use rtl_fm, a command line FM demodulator.
On the RTL2832U dongle side, he modified the RTL2832U Linux DVB-T drivers (not the SDR drivers) to work on the 1.3 GHz band. The intention of this camera is for it to fly on a rocket mission. In the YouTube video below he has uploaded some sample footage with the RTL2832U dongle receiving the stream from 300 meters away.
YouTube user Brad Bowers has posted a video showing GQRX running on his BeagleBone Black with an RTL-SDR dongle. The BeagleBone Black is an embedded Linux computer, similar to the Raspberry Pi, but with significantly more processing power. He found that GQRX actually performed quite responsively on the BeagleBone.