how to use Gqrx for low frequency or baseband with RTL-SDR or sound card

[Martin Muc]

I would like to use the Gqrx GUI for low frequency signals either using my RTL-SDR in baseband mode, or using my sound card.  But I cannot find information or documentation on this either by googling or on the gqrx.dk/doc/ provided documents.

On the feature list here http://gqrx.dk/, it lists the feature to "Record and playback raw baseband data."

However when I start Gqrx (v. 2.3.1 on Ubuntu) and choose the I/O device as "Realtek RTL2838UHIDIR", I cannot tune below 24 MHz.  (I see the spectrum and waterfall and can hear FM stations so the hardware and antenna are working.)

Or for the sound card approach, when I choose File > I/O Devices, my (several) sound card inputs are not listed (front panel mic, rear panel mic, rear panel line-in, etc).

The readme, while from an older version, says ( https://sourceforge.net/projects/gqrx/files/1.9.158/ ) it can use any sound card:

   "Technically, gqrx can use any soundcard as input device but the sample rate is fixed at 96 kHz (bug)."


I would appreciate any direction on how I can get this to work or find relevant documentation, how-tos, etc.

Martin

[David Ranch]

Gqrx doesn't support raw sound cards today:

   https://github.com/csete/gqrx/issues/13

If you want to use your RTL dongle in baseband mode, you can consider the direct sampling hack - http://www.rtl-sdr.com/rtl-sdr-direct-sampling-mode/ or consider an upconverter like the HamItUp http://www.nooelec.com/store/ham-it-up.html or other similar solutions.


--David
KI6ZHD