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I was testing the Gqrx FM stereo code by Alex Grinkov using an RTL-SDR dongle when I noticed that the recently added auto-gain in the driver can be quite useful.

About a year ago I posted a step-by-step guide about how to receive NOAA APT weather satellite images using Gqrx SDR and the Funcube Dongle. Today, I tried to repeat the procedure using my ezcap eztv666 rtlsdr dongle with very good results.

Support for RTL2832U-based DVB-T dongles and USRP devices from Ettus Research is now available in the Gqrx source code repository.

Support for RTL2832U-based DVB-T devices is available via the rtl-sdr and gr-osmosdr libraries. This also provides support for Ettus Research USRP's if the gr-uhd package has been installed prior to compiling gr-osmosdr. A complete build from scratch that would support all hardware devices would thus include the following steps:

Here is a new recording showing an updated Gqrx receiving the FO-29 amateur radio satellite using the Funcube Dongle. Previous recordings used an early version of Gqrx. It was a very quiet pass, most notable thing was probably the Russian and Spanish hams using FM. They probably don't have a clue that their signal comes over a satellite transponder. Another video recording focusing on the FM transmissions during this FO-29 pass is available here.

I don't think I ever posted a video showing the built-in AFSK1200 demodulator and decoder in Gqrx, so here it is. The video show local APRS traffic in Copenhagen on a Sunday afternoon. I also tried to receive from the ISS but nothing heard this time.

Here is a short demo showing how to receive broadcast FM with Gqrx. This demo uses the Funcube Dongle, which is really not suited for broadcast FM reception. Gqrx does not employ any tricks to make it sound like it works properly – it just does straightforward FM demodulation with wide FM parameters and you will hear the lack of sufficient bandwidth as distortion on some stations (not all though).

Last week I have tested the RTL2832U-based ezcap EzTV666 DVB-T dongle on the air using various VHF signal.

RTL2832U-based DVB-T dongles are now supported by Gqrx SDR, see this announcement!

You may have noticed the recent buzz on the internet about using cheap DVB-T dongles as software defined radio receivers. It all started on this mailing list when V4L/DVB kernel developer Antti Palosaari discovered that the ezcap EzTV 668 DVB-T/FM/DAB USB dongle, which is based on the RTL2832U chip, can be used to stream raw I/Q samples to the host computer. It is in fact the way the device supports FM and DAB reception; raw I/Q is sent to the host where the application does the demodulation.

Just a quick note that Gqrx now uses pulseaudio for all audio I/O, which includes I/Q input from the Funcube Dongle.

One of the great advantages of software defined radio receivers is that tuning receiver settings is a matter of adjusting software parameters. Gqrx is no different here and has optimal settings built in for weather satellite reception. This tutorial describes how to receive automatic picture transmissions (APT) from NOAA weather satellites using Gqrx SDR, record them to a WAV file, and finally decode the images using the free and open source Atpdec decoder. If you follow this guide you can end up with very nice results such as the one shown at the end.