Kalibrate, or kal, can scan for GSM base stations in a given frequency band and
can use those GSM base stations to calculate the local oscillator frequency
offset.

See http://thre.at/kalibrate 

Copyright (c) 2010, Joshua Lackey (jl@thre.at)

Copyright (c) 2012, Steve Markgraf (steve@steve-m.de) 

modified for use with hackrf devices,
Copyright (c) 2014, Wang Kang (scateu@gmail.com) 
http://hackrf.net  : A Chinese HackRF Community


2014-8-23 Update:

Thanks to chris.kuethe@gmail.com who did a bunch of tinkering with this port of kalibrate.

https://github.com/ckuethe/kalibrate-hackrf/

This now runs as fast as kalibrate-rtl


2015-3-3 Update:

Add ability to specify channel when scanning to check power output for a single channel.

Author: [xorrbit](https://github.com/xorrbit)