Signal Watchdog

Signal Watchdog continuously checks a list of frequencies or frequency bands and reports whether each is clear or occupied. Editions are available for RF Explorer and RTL-SDR.

Getting started

  1. Select Frequencies or Bands in the title bar.
  2. Set the sweep Start, Stop, and Threshold values.
  3. Add, edit, and label the rows you need to monitor.
  4. Check the rows that should be active.
  5. Press Start.

How readings are made

  • In Frequencies mode, the reading is the strongest signal within approximately ±75 kHz of the specified frequency.
  • In Bands mode, the reading is the strongest signal between the row’s Start and Stop frequencies.

Only checked rows that fall inside the current sweep range are measured.

Reading the table

  • Watch checkbox — enables measurement for that row.
  • Frequency / Start / Stop — editable while scanning is stopped.
  • Amplitude — the current peak level. Green is at or below the threshold; red is above it.
  • Description — a user-defined label such as a performer, device, or broadcast channel.
  • History — the last 100 sweeps, with green and red samples moving from left to right.

A sustained run of red indicates persistent occupancy; occasional red points reveal intermittent activity.

Threshold and receiver accuracy

The threshold separates “clear” from “occupied.” RF Explorer supplies calibrated dBm readings. RTL-SDR amplitudes use a nominal reference and should be treated as approximate; they remain useful for presence/absence monitoring and relative comparison.

Lists and reporting

The ⋮ menu provides Save, Load, Add Row, and Remove Row commands for reusable JSON watch lists. Choose Save as PDF to download a timestamped report.