Problem:
Most of the "LoRaWAN 868 MHz antenna"'s are in deed 900 MHz P-GSM antennas.

Solution:
Measure the SWR with NanoVNA.
The results are in Messung "868 MHz"-Antennen

Error:
Networks with channel number 12 or channel number 13 were not found.

Problem:
As default, only "worldwide allowed channels" 1..11 are configured.

Solution:
start_channel = 1
stop_channel = 13
wifi.radio.start_scanning_networks(start_channel=start_channel, stop_channel=stop_channel)


Error:
"Kernel driver is active, or device is claimed by second instance of librtlsdr.
In the first case, please either detach or blacklist the kernel module
(dvb_usb_rtl28xxu), or enable automatic detaching at compile time."

Problem:
Raspberry Pi OS "bookworm" (Debian version 12) ignores /etc/modprobe.d/blacklist.conf

Solution:
cmake ../ -DINSTALL_UDEV_RULES=ON -DDETACH_KERNEL_DRIVER=ON

Hints:
speaker-test -c2 -twav
Listen to a radio station with
rtl_fm -f 94.4M -s 192000 -r 48000 | aplay -r 48 -f S16_LE -t raw -c 1
or
rtl_fm -f 94.4M -s 192000 -r 48000 | play -t raw -r 48k -es -b 16 -c 1 -V1 -