WSPR-RX with RTL-SDR and GQRX on Debian 10/11

01.06.2022 Test on Debian 11 with success.

1. Hardware
RTL-SDR RX 100KHz-1.7GHz UV HF USB Tuner R820T+8232
(RTL-SDR-box with 2 SMA-inputs (0.1 - 30 MHz direct sampling and 30 -1700 MHz) and Mini-USB connector)
PC (i386 or amd64) > 1GHz Cl.F., > 1GB RAM

2. Software
Debian 10 or 11, WSJT-X, GQRX-SDR

3. Installation
System and WSPR, for example: Debian 10 and WSJT-X,  Linux Mini-PC Setup for 24/7 WSPR RX/TX Operation

Open a terminal as root and confirm you are in your home directory.
Type the following commands:
apt-get update
apt-get install pkg-config
apt-get install git
apt-get install cmake
apt-get install build-essential
apt-get install libusb-1.0-0-dev
git clone git://git.osmocom.org/rtl-sdr.git
cd rtl-sdr/
mkdir build
cd build
make install
cp ../rtl-sdr.rules /etc/udev/rules.d/

Blacklist the default driver as root:
gedit (xedit, nano, ...) blacklist-rtl.conf
blacklist dvb_usb_rtl28xxu
Save the file in the directory /etc/modprobe.d
Restart and test the drivers with
rtl_test -t

If you see:
Found 1 device(s)
0: Realtek, RTL 2838UHIDIR, SN: 00000001
the drivers and the rtl-sdr-usb-box will work.

My 2 RTL-SDR-Boxes did not work properly with a single USB-Cable. It seems to me that the DC current provided by one USB socket to the RTL-SDR is near the limit and not high enough. This problem was solved when I replaced the single USB-Cable with an USB-Y-Cable (2xUSB A male - 1xUSB-Mini male).

Installing GQRX:
Type as root:
apt-get install gqrx-sdr

The GQRX AF output has to be connected to the AF input of WSJT-X. A less elegant hadware solution is to connect Speaker/Headphone out  to Line in accepting a double conversion of the AF signal. The better way is a software solution. Under Windows I used the program Virtual Audio Cable. With Debian 10/11 it's easy to install a permanently existing virtual Audio Connection with the pulsaudio sound server.
Open the configuration file (type as root: gedit /etc/pulse/default.pa) and add the following line:
load-module module-null-sink sink_name=Virtual_Sink sink_properties=device.description=Virtual_Sink
Save the file and restart.

4. Settings:
Connect the RTL-SDR to the USB socket, start GQRX and open File / I/O Settings.
Select/modify the following values:
device Realtek RTL2838UHIDIR
device string rtl=0
if you want to operate in thr range of 0,1 - 30 MHz:
audio input settings, device Virtual_Sink
Receiver options:
Channel filter offset 0
Mode  LSB, USB,AM, FM etc., USB for WSJT-X.

Start WSJT-X , go to File/Settings/Audio and select Virtual_Sink.monitor as input. Don't forget to press Ok.

That's all. Have fun!.