kalibrate-rtl

Kalibrate, or kal, is designed to scan for GSM base stations within given frequency bands and utilize detected stations to compute the local oscillator frequency offset of RTL-SDR devices. This calibration is crucial for precise tuning in radio frequency applications, particularly when working with software-defined radios like ezcap USB 2.0 DVB-T/DAB/FM dongles equipped with Rafael Micro R820T tuners.

Common use cases include initial scanning to identify active GSM channels and their power levels, followed by targeted offset calculations on specific channels to determine ppm errors. This helps in compensating for hardware inaccuracies in SDR setups used for signal analysis or monitoring in GSM-850, GSM900, DCS, PCS, and other supported bands.

The tool supports both automated scanning and manual specification of frequencies or channels, making it versatile for field calibration of RTL-SDR hardware in wireless security and RF research contexts.

kalibrate-rtl uses RTL-SDR devices to capture GSM signals in specified bands like GSM850. It scans for base stations by analyzing signal power on ARFCN channels, displaying frequency, offset, and power levels. For calibration, it tunes to a selected channel, measures sample rate precisely (e.g., 270833.002142 Hz), and computes clock frequency offset by averaging deviations (e.g., -4.093kHz, 4.709 ppm), accounting for initial errors and overruns.