This step is optional, from my experience, NooElec receivers don't need calibration.
Calibration stepsinstructions below are taken from the following guide.
mkdir ~/kal
cd ~/kal
sudo apt-get install libtool autoconf automake libfftw3-dev
git clone https://github.com/asdil12/kalibrate-rtl.git
cd kalibrate-rtl
git checkout arm_memory
./bootstrap
./configure
make
sudo make install
Make sure your antenna is connected to the RTL-SDR receiver and the receiver is connected to the Raspberri Pi. You should not use the band-pass filter yet.
To calibrate, run:
kal -s GSM900 -d 0 -g 40
You'll see something like:
Found 1 device(s):
0: Generic RTL2832U OEM
Using device 0: Generic RTL2832U OEM
Found Rafael Micro R820T tuner
Exact sample rate is: 270833.002142 Hz
[R82XX] PLL not locked!
Setting gain: 40.0 dB
kal: Scanning for GSM-900 base stations.
GSM-900:
chan: 16 (938.2MHz - 303Hz) power: 764382.95
chan: 29 (940.8MHz - 107Hz) power: 3099720.22
chan: 37 (942.4MHz + 351Hz) power: 814043.05
chan: 56 (946.2MHz - 106Hz) power: 255238.03
chan: 65 (948.0MHz - 115Hz) power: 645372.85
chan: 69 (948.8MHz + 115Hz) power: 4609305.74
chan: 73 (949.6MHz + 239Hz) power: 642985.06
chan: 102 (955.4MHz - 512Hz) power: 694681.27
Use the most powerful channel (69 in the example above) for calibration
kal -c -d 0 -g 40
You'll get something like:
Found 1 device(s):
0: Generic RTL2832U OEM
Using device 0: Generic RTL2832U OEM
Found Rafael Micro R820T tuner
Exact sample rate is: 270833.002142 Hz
[R82XX] PLL not locked!
Setting gain: 40.0 dB
kal: Calculating clock frequency offset.
Using GSM-900 channel 69 (948.8MHz)
average [min, max] (range, stddev)
+ 64Hz [39, 87] (49, 13.600428)
overruns: 0
not found: 0
average absolute error: -0.067 ppm
Note the "average absolute error" number. If you have it around 0, everything's fine.
If not, you may need to change the frequency when you start dump1090.