Signal Watchdog
Signal Watchdog keeps an eye on the specific frequencies or bands you care about and shows, at a glance, whether each one currently has a signal above the threshold you set — with a rolling history beside every entry, so you can see when it came and went.
It is for watching a known set of channels — a group of wireless microphones, a control or telemetry link, a repeater — and catching the moment something appears or drops out, rather than staring at a full spectrum. Is my channel clear, or is something on it?
Signal Watchdog comes in two versions on the menu, one for each receiver. They look and work the same; this page covers both, and a box like the one below marks every place they differ.
- Signal Watchdog for RF Explorer — a calibrated analyzer. Levels are true dBm.
- Signal Watchdog for RTL-SDR — a low-cost USB receiver. It is uncalibrated: levels are approximate (see Threshold below). For "is something there or not" it works just as well.
Getting started
- Plug the receiver into the Wireless Toolbox, then open the tool from the menu.
- Pick a view with the Frequencies / Bands toggle in the title bar.
- Set the sweep range with START / STOP (MHz) and a THRESHOLD (dBm) in the left panel.
- Check the rows you want to watch, then press Start (top-right). START, STOP, THRESHOLD and the Frequencies / Bands toggle are locked while scanning — press Stop to change them.
How a reading is made
The Wireless Toolbox sweeps the START–STOP span and, for every checked row, measures the strongest signal in that row's slice of the spectrum:
| View | Reading |
|---|---|
| Frequencies | The peak within about ±75 kHz of the frequency. |
| Bands | The peak anywhere between the band's Start and Stop. |
The table
| Column | Meaning |
|---|---|
| ☑ | Watch this row. Only checked rows are measured. |
| Frequency / Start / Stop | Editable. Tap to type a new value (while stopped). |
| Amplitude (dBm) | The current reading as a bar. Green = at or below the threshold (clear); red = above it (occupied). |
| Description | Editable label, e.g. the performer or channel. |
| History | The last 100 sweeps as dots — green (clear) or red (occupied) — marching left to right, newest at the leading edge. A run of red means a persistently occupied channel. |
Threshold
The THRESHOLD (dBm) is the line between "clear" and "occupied". A yellow line marks it on the trace at the top, and each row's bar and history dots are coloured against it. Lower it to be stricter about what counts as interference: more signals will then read as occupied.
Status bar
| Field | Meaning |
|---|---|
| MODE | Frequencies or Bands. |
| MONITORED | How many rows are being watched. |
| ABOVE THRESHOLD | How many of them are occupied right now. |
| SPAN | The range being swept. |
| STATUS | Whether a scan is running. |
If the readings stop updating
If the receiver stops sending data while a scan is running, Signal Watchdog says so on the page. Switch the RF Explorer off and on with its own power switch, or unplug the RTL-SDR and plug it back in; then return to the menu and start the tool again.
Menu (⋮)
- Save as PDF — see below.
- Save… / Load… — save the current list to a file on your phone or computer (watchdog_frequencies.json or watchdog_bands.json), or load one back.
- Add Row / Remove Row — add a blank row; Remove deletes the selected row (tap a row to select it first).
- About — version information.
The ☰ button (top-left) returns to the Wireless Toolbox menu.
Save as PDF
The ⋮ menu (top-right) has Save as PDF. It captures the tool exactly as shown and writes one file to your device’s Downloads folder, named with the tool and a timestamp, e.g. SignalWatchdog 2026-08-13 14.32.05.pdf. Every save is timestamped, so nothing is overwritten.