Enabling bias tee option for FLARM reception

[WeKnowMC]

I have recently purchased an RTL-SDR blog V3 dongle as well as an Uputronics filtered preamp to improve my FLARM reception. The RTL SDR V3 dongle has a built in bias tee which can be used to power the Uputronics preamp - I believe it can be enabled via the pi. I see many people are using this setup, judging by the OGN google group. I am wondering how would I enable this bias tee option within the PilotAware image. I am running on a raspberry pi 2 and version 20180428.

[Admin]

Can I ask how you would do this for a standard OGN installation ?

The method will be the same but just need to get the disk in a writeable mode

# put the disk in a writable mode
$ /root/mount_rw.bash

# do all the necessary changes to the configuration for new SDR

# put the disk in a non-writable mode
$ /root/mount_ro.bash

thx
Lee

[WeKnowMC]

I have found some instructions on the OGN wiki about enabling the bias tee, at the bottom of this page: http://wiki.glidernet.org/wiki:manual-installation-guide

It states that a custom driver is needed and the old one needs to be removed by doing
$ sudo apt-get remove --purge rtl-sdr
I have tried this but I get "Package 'rtl-sdr' is not installed, so not removed" which leads me to think that the rtl-sdr driver in the PilotAware image has compiled/installed in another way.

So firstly, does anyone know how to remove the already existing drivers before I can install the custom ones? I know that the already existing drivers don't support the bias tee option because doing
$ rtl_biast -b 1
to manually enable the bias tee until the next reboot will return "rtl_biast: command not found".

[WeKnowMC]

Managed to get this working - here is what I did for those who may be looking to do the same thing...

# put the disk in a writable mode, as Lee said
$ sudo /root/mount_rw.bash

# stop service
$ sudo service rtlsdr-ogn stop

# remove the current RTL SDR install
$ cd ~/rtl-sdr/build
$ sudo make uninstall
$ cd ~
$ sudo rm -R rtl-sdr

# install new drivers - instructions taken from the OGN google group
$ git clone https://github.com/rtlsdrblog/rtl-sdr
$ cd rtl-sdr
$ mkdir build
$ cd build
$ cmake .. -DCMAKE_INSTALL_PREFIX=/usr -DINSTALL_UDEV_RULES=ON
$ make
$ sudo make install

# I ran into problems with a conflicting file so I renamed it to something else which fixed the problem
$ sudo mv /usr/lib/arm-linux-gnueabihf/librtlsdr.so.0 /usr/lib/arm-linux-gnueabihf/my_librtlsdr.so.0

Then I added BiasTee = 1; in the RF section of the OGN config file located at ~/rtlsdr-ogn/rtlsdr-ogn-paw.conf

# start service
$ sudo service rtlsdr-ogn start

# put the disk in a non-writable mode, as Lee said
$ sudo /root/mount_ro.bash

Then I confirmed the bias tee was working by measuring 4.5V on the SMA connector of the dongle