Tagged: gqrx

Combining the bandwidth of multiple RTL-SDRs: Now working in GQRX!

A few days ago we posted how Oliver, an RTL-SDR experimenter, managed to (incoherently) combine the bandwidths of two RTL-SDR dongles to create a 4.4 MHz FFT display in GNU Radio. Now Oliver has taken this idea further and produced an updated version of his GNU Radio program

Oliver’s GNU Radio program is now capable of combining four RTL-SDR dongles and is now also capable of piping the output via a FIFO to GQRX. With four RTL-SDR dongles you can get a total bandwidth of 8.4 MHz. He also writes that it is even possible to listen to analog signals that are in overlapping areas.

Four RTL-SDRs producing a total of 8.4 MHz of bandwidth in GQRX.
Four RTL-SDRs producing a total of 8.4 MHz of bandwidth in GQRX.

Installing GQRX on Mac OSX

Mac OSX users can have a hard time with the RTL-SDR as there are not many software packages available for it. One software package that is known to work well on OSX is GQRX, which is a general multi mode receiver GUI that is similar to the Windows software SDR#. Over on smittix’s blog, the author has created a post showing how to install the latest version of GQRX on OSX. The installation involves using Macports, a system that allows some open source programs like GQRX to be automatically compiled and installed on OSX.

GQRX running on a Mac Computer
GQRX running on a OSX Computer

RTL-SDR with GQRX Running on an Odroid C1 at 1 MSPS and Max FFT

Over on YouTube user neutron2025 has uploaded some videos showing GQRX running on an Odroid C1. The Odroid C1 is a low cost ($35 USD) mini computer with an Arm Cortex A5 quad core CPU and 1 GB RAM which runs Ubuntu 14.04 or Android KitKat. It is a much more powerful competitor to the Raspberry Pi which also goes for around the same price.

Despite its low cost, the video by neutron2025 shows that the Odroid C1 has enough processing power to run the relatively CPU intensive GQRX SDR software with the RTL-SDR at a 1 MSPS sampling rate and maximum FFT resolution.

To install GQRX, GNU Radio also needs to be installed. Installation of GNU Radio is a lengthy process containing many writes to the file system. The amount of writes that occur could destroy a SDCard. To get around this neutron2025 connected an external hard drive and used that as a swap file while installing GNU Radio. His installation notes can be found on pastebin. He writes that installation took around 8 hours.

odroid c1 gqrx
RTL-SDR / Odroid C1 / GQRX / 2msps / Max FFT

Demonstrating GQRX Running on a BeagleBone Black with RTL-SDR

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.

Beagle Bone Black as Rtl-SDR front end with gqrx

HackRF Decoding PICO High Altitude Balloons (HAB)

Blogger g0hww shows us how he used his HackRF to decode Pico high altitude balloon (HAB) transmissions using gqrx and dl-fldigi. Pico balloons are small party sized high altitude balloons, typically launched by hobbyists. They have enough lift to carry a small sized ~60g payload. Since they are so small, they are usually exempt from requiring permission from the authorities, unlike full sized weather balloons.

The cheaper RTL-SDR could also be used to track these balloons.

PICO High Altitude Ballo0n Recevied with HackRF