Extract from Adafruit RTL-SDR Scanner

Install image with PiTFT 3.5" (se this)

run raspi-config

sudo raspi-config

exit and reboot

Install dependencies:

sudo apt-get update
sudo apt-get install cmake build-essential python-pip libusb-1.0-0-dev python-numpy git

Install RTL-SDR library:

cd ~
git clone git://git.osmocom.org/rtl-sdr.git
cd rtl-sdr
mkdir build
cd build
sudo make install
sudo ldconfig

Blacklist dev_usb_rtl28xxu (this was required for me) - Edit or create blacklist.conf:

sudo nano /etc/modprobe.d/raspi-blacklist.conf

add the following content

blacklist dvb_usb_rtl28xxu

Save and exit editor

Install RTL-SDR Python wrapper

sudo pip install pyrtlsdr

Get the source code

cd ~
git clone https://github.com/adafruit/FreqShow.git
cd FreqShow

Run the program (from keyboard on pi - not from ssh!):

sudo python freqshow.py

To autostart scanner at boot, insert into /etc/rc.local

sudo nano /etc/rc.local 

Insert on line before 'exit 0'

cd /home/pi/FreqShow
/usr/bin/python freqshow.py

save and exit editor