Open Source Close Call Monitor for RTL-SDR

Thank you to Fabian for writing in and sharing with us his newly released RTL-SDR close call monitoring software called "rtl-sdr-close-call-monitor". The software is open source and written in Python. It's main purpose is to log any signal peaks that appear within a defined frequency range. Over on the GitHub Fabian explains the software:

These scripts use an RTL-SDR device to detect peak signals on a user specified frequency range. The scripts can also make an automatic blacklist so that different sources of RF noise won't cause continuous false positives. There are two scripts provided as examples. The scripts can be used to monitor certain frequencies for a wide range of purposes such as:

  • In criminal investigations, a close-call RF signal monitor can be used to detect and track communication signals used by criminals. This can help law enforcement agencies gather intelligence and evidence, and even prevent future crimes from being committed. By analyzing the frequency and strength of signals emitted by communication devices, a close-call RF signal monitor can provide valuable insights into the movements and activities of suspects, allowing investigators to piece together a timeline of events and make informed decisions about how to proceed with a case.
  • In military operations, a close-call RF signal monitor can be used to identify and track enemy communication signals, providing valuable intelligence for strategic decision-making.
  • In scientific research, a close-call RF signal monitor can be used to collect and analyze data related to wireless communication systems, providing valuable insights for thesis projects and other research studies.
An excerpt of Fabian's close call monitoring Python code.
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a windows binary would be nice…


For what exactly?


a dedicated application for just close call under windows. detect only nearfield transmission with amazing scanning speed…


But by the looks it, it’s only monitoring a ~2 MHz band. Not very useful.


The RTL-SDR has a stable bandwidth of 2.56MHz, which is limited by the hardware. Therefore, it’s not the script that determines the maximum bandwidth, but rather the capabilities of the device itself.

Erlend / LB6MI

Sure, but it can actually power-detect a 10 or maybe 20 MHz span.
The clue is to override normal operation and hijack the tuner!

Useable for a fast pre-scan, before running a more detailed scan to find the exact frequency.