December 2015 – Gqrx SDR

Gqrx 2.4 released

One year after the 2.3.2 release, Gqrx 2.4 is now available for download. This release includes both new features, important bug-fixes as well as improvements of existing functionality.

New features

Bookmarks.
FM RDS decoder using gr-rds.
Frequency tooltips on the FFT area (disabled on Mac).
Filter shape selector (soft, normal, sharp).
Slider to aid zooming on the frequency and dB axes.
RFSpace Cloud-IQ support (still work in progress).
OIRT stereo decoder (Daniil Cherednik).
Input decimator.

Bug fixes

Prevent crash due to device errors while starting the application.
Use hardware frequency in IQ file names.
FFT averaging (it can now be disabled).
“Could not resolve pattern10600” error messages in the terminal.
Antenna selection error with USRP B210 (Ethan Trewhitt).
LNB LO value not updated in I/O config dialog.
Initial gain of rtlsdr devices is no longer 0 dB.
DSP freeze when setting FM de-emphasis time constant to 0.
Use correct main category in desktop entry file.

Improvements

Support up to 1M point FFT.
Fractional PPM correction.
AGC performance.
FFT performance.
Right click on frequency digit to clear digits.
Robustness against malformed remote control commands.

Ubuntu Packages

Starting with this release, we have a new PPA that contains only Gqrx binaries and uses MyriadRF PPAs for GNU Radio and SDR driver packages. I realize this is inconvenient for existing PPA users; however, this offloads some of the packaging work from me and will ensure more up to date GNU Radio packages for Ubuntu users in the future.

Please make sure you have the previous PPA disabled and old, obsolete packages removed before using the new PPA as instructed on the Ubuntu Install page. Feel free to contact us if you need help with the PPA transition.

Mac OS X binaries

As always, there is an up to date Gqrx package in Macports. There is now also an app bundle available from GitHub or SourceForge. The bundle was built on Mac OS X El Capitan and contains all required third part libraries, as well as the command line utilities that come with the Airspy, RTL-SDR, Hackrf and Bladerf driver libraries. See the included README for details.

Installing from source

The source code can be downloaded from GitHub or SourceForge. Starting with this release, gqrx can also be compiled using cmake, see the README file for details. Building with qmake is still available and will not disappear any time soon, so feel free to use either method.

Have fun!

Meteor scatter reception with RTL-SDR and Gqrx

Meteor scatter, or meteor burst communications, is a challenging field within amateur radio communication, where the operators use the ionized trails of meteors for reflection of radio waves.

George Smart, M1GEO, has posted a very nice write-up on his website describing the setup that he uses for meteor scatter reception. The setup uses an RTL-SDR dongle with Gqrx as receiver, and WSJT or MSHV for decoding.

Meteor Scatter reception setup by M1GEO. Image credit: M1GEO.

Check out Meteor Scatter Reception on RTL-SDR.

Satellite telemetry decoding on Linux

Are you interested in receiving and decoding telemetry from amateur radio satellites? Then check out this excellent article by Jan PE0SAT called Unix TLM (Telemetry) decoding, where Jan gives a description of his setup.

In his Linux setup, Jan uses Gqrx as SDR front-end and Gpredict to track the satellites. As we wrote earlier, Gqrx has a Hamlib-compatible TCP interface so that we can use Gpredict to adjust the receiver frequency with Doppler corrections.

PE0SAT Linux telemetry receiver setup. Image credit: PE0SAT.

Jan also takes advantage of the Audio/UDP interface in Gqrx as well as the audio routing capabilities of modern Linux desktops to route the demodulated audio from Gqrx to external decoder applications.

All in all, this is a very nice setup that demonstrates well how Gqrx can be hooked up with external applications to get new functionality.