GQRX 2.17.6 & NESDR Smart

[Chris L]

Having some issues that I can't figure out...

Trying to run GQRX from terminal and I get "failed to set input device, wrong rtlsdr device index given" when I choose the RTL-SDR that doesn't have the 's/n' listed in the name and I get "failed to set input device, failed to set default sample rate" when I select the device listed without 's/n' in the name. The program will load but I don't have receiver settings.If I try to run sudo gqrx then I get 'Audio Error......connection refused'. 

I have the UDEV rules installed and the USB dongle was working on my windows machine the last time I tried it.

It does show up (sometimes) with lsusb as Realtek Semiconductor Corp. RTL2832U DVB-T.

Thoughts?

[Roger David Powers]

Do "sudo apt install rtl-sdr" then run rtl_test first as non-root then as root.  

If root is necessary then it's still a permission/udev problem.  That is my guess.  

Maybe post the udev rules you use, as well as the output of lsusb?

The ID in the lsusb output is important, the udev rules need to have a matching entry, and SMART may not be in their list.

For instance my rules have:

SUBSYSTEMS=="usb", ATTRS{idVendor}=="0bda", ATTRS{idProduct}=="2838", ENV{ID_SOFTWARE_RADIO}="1", MODE="0660", GROUP="plugdev"

And my device is:

Bus 001 Device 003: ID 0bda:2838 Realtek Semiconductor Corp. RTL2838 DVB-T

The audio error as root is expected, it means your desktop is started as non-root then you are trying to use an app as root and it won't connect due to the different users.  Using rtl_test removes the audio problem since it doesn't try to output any audio.

You also might need to blacklist the default 'dvb' driver for the rtl-sdr devices:

echo 'blacklist dvb_usb_rtl28xxu' | sudo tee --append /etc/modprobe.d/blacklist-dvb_usb_rtl28xxu.conf

then reboot.

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[Robin Gape]

Blacklisting kernel modules should be no longer necessary since Ubuntu 16.04, since the kernel module was updated.

Extract from a note written in 2019:

Adapted from an instructables page¹, a short note², other sources, and direct experience. Compilation from source, blacklisting kernel modules, and establishing udev rules are generally no longer necessary.

Kernel modules & udev rules

From Ubuntu 16.04 LTS the necessary udev rules are installed as part of librtlsdr0. A recently developed kernel module³, rtl2832_sdr allows both intended and direct sample capability, by unloading any conflicting kernel module⁴ when necessary.

Module blacklisting is no longer required!

1Found at http://www.instructables.com/id/rtl-sdr-on-Ubuntu/.

2See https://ranous.files.wordpress.com/2016/03/rtl-sdr4linux_quickstartv10-16.pdf, at https://ranous.wordpress.com/.

3Installed as part of the standard Linux kernel.

4As can be seen with the kernel driver messages when rtl_test is run. See below.

These days rtl_test, rtl_fm, and the various rtlsdr driver libraries swap the kernel module in & out automagically. Much less hassle.

73,

Robin, G8DQX