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kalibrate-rtl

Measures an SDR dongle's frequency error against GSM base stations

What it does

Measures how far off frequency an RTL-SDR dongle actually is, by listening to a GSM base station — whose carrier is disciplined to a far better reference than anything in a ten-dollar tuner — and reporting the error in parts per million. That number goes into the -p option of most SDR tools.

Why you would want it

A cheap dongle's crystal can be tens of ppm out, which at 145 MHz is a kilohertz or more: enough to put a narrow FM signal off-centre and enough to stop a decoder locking at all. Calibrating once and recording the figure makes every other tool in the catalog more accurate, and it costs one measurement.

Before it will work

An RTL-SDR dongle and an antenna that hears a GSM downlink — GSM900 or GSM850 depending on region. It only listens; it transmits nothing.

How it installs

  • apt: kalibrate-rtl — on kali
  • Kali ships 0.4.1+git20191125-0kali2, which is the same revision the source block below pins — deliberately, so an apt install and a source build are the same software rather than two.
  • git (autotools) — https://github.com/steve-m/kalibrate-rtl at 66074b82daf4a1c588ce1c565a145fac1c59ec56
  • build dependencies: build-essential, autoconf, automake, libtool, pkg-config, librtlsdr-dev, libfftw3-dev

Known problems

It depends on GSM being on the air, and GSM has been switched off in a growing number of countries. Where there is no GSM carrier to hear, this tool cannot measure anything and the alternative is a known local beacon or a signal generator. Upstream is dormant — last commit 2022-02-01 — but the tool is small and does one thing, and "finished" is a legitimate state for software to be in (PARITY-POLICY.md).

Keeping it current

  • probe: none
  • strategy: manual
  • Dormant, not dead: last commit on the default branch 2022-02-01, and no tags have ever been cut (verified 2026-08-28 from the branch head, not GitHub's updated_at — D-032). Nothing to poll, so the pin is reviewed on its cadence rather than chased.

Where to get help with the software itself

GitHub issues, though the repository has been quiet since 2022. Kali's packaging is the more actively maintained artefact.

Source: catalog/packages/kalibrate-rtl.yaml