openwebrxplus-plugins

This receiver plugin adds a high-performance frequency scanner to OpenWebRX+. It uses FFT-based “Virtual Scanning” to analyze the waterfall data and jump directly to active signals. It includes features like a blacklist, digital signal filtering, and multiple scan modes.

Preview

Load

Add this line in your init.js file:

//remote
Plugins.load('https://0xaf.github.io/openwebrxplus-plugins/receiver/freq_scanner/freq_scanner.js');
// local
Plugins.load('freq_scanner');

Usage

A small SC button is added to the bottom left of the receiver panel. Clicking this button opens a floating, draggable window containing the scanner display and controls.

SC Button Status

• Grey: Scanner is stopped and window is closed.
• Green: Scanner window is open.
• Yellow: Scanner is running in the background OR “Always Show Blocked Ranges” is active (window closed).
• Yellow Border: “Edit Blocks” mode is active (can move/resize ranges via touch).

Scanner Display

The display area uses red text on a deep blue background:

• Ready: The scanner is currently stopped.
• Scanning…: The scanner is actively searching for signals.
• Frequency / Name: When a signal is detected, the frequency is displayed. If the frequency matches a bookmark, the bookmark name is shown instead.
• wait: A small “wait” indicator appears when the scanner is holding on a frequency during the delay time (after signal loss) before resuming the scan.

Scanner Window Buttons

• Scan: Start or Stop scanning.
  • Long Click (> 800ms): Opens the Scan Options menu (indicated by a triangle).
• Skip: Skips the current frequency (only active when scanning).
• Block: Adds the current frequency to the blacklist.
  • Long Click (> 800ms): Opens the Block Options menu (indicated by a triangle).
• Setup: Opens the Scanner Setup & Blacklist menu.

Scan Options (Scan Button)

• Scan Modes:
  • Normal (Carrier): Stays on frequency while a signal is present (plus a short delay).
  • Stop on signal: Stops scanning completely when a signal is found.
  • 10s Sample: Listens for 10 seconds, then continues scanning regardless of the signal.
• Detection Logic:
  • Standard (Squelch): Simple detection based on the UI squelch slider.
  • Width Filter (<= Bandwidth): Intelligent detection that adapts to your current filter width (e.g., NFM, AM). It ignores signals wider than your filter or narrower than 20% of it. It also features Plateau Detection to skip broad noise and Split-Peak Detection to correctly identify digital twin-carrier signals.
• Ignore Squelch Slider (Auto): Only available with “Width Filter”. If enabled, the scanner ignores the manual squelch slider and uses an internal SNR-based threshold to find even very weak signals automatically.
• Delay: Set the wait time after signal loss (Standard, 5s, 10s).
• Dwell Time: Slider to adjust how long the scanner stays on a frequency to verify a signal before moving to the next peak. Increasing this helps with slow FFT updates or weak signals.
• Filter: Only Analog: If enabled, the scanner automatically skips frequencies marked as digital (DMR, YSF, D-Star, etc.) in your bookmarks.

Block Options (Block Button)

• Clear Visible Blocked Ranges: Removes all blacklist entries that are currently visible in the waterfall view.
• Remove Blocked Range: Allows you to remove a specific blocked range or frequency by clicking on it in the waterfall.
• Block Range: Allows you to select a frequency range on the waterfall to block. Click and drag to define the range.

Scanner Setup (Setup Button)

• Always Show Blocked Ranges: If enabled, blocked frequencies and ranges are visualized as colored bars on the waterfall even when the scanner is not running.
• Edit Blocks (Move/Resize): Enables interactive manipulation of blocks. Drag the edges to resize the range or the center to move it.
• Color Picker: Choose from different colors for the blocked range visualization (Red, Orange, Yellow, Green, Blue, Purple, White).
• Export / Import Plugin Settings: Save or load the plugin configuration including the blacklist (JSON).
• Manage Blacklist: Opens a dialog to manually manage the blacklist entries.
• Clear Blacklist: Removes all blocked frequencies.
• Audio Sync: Slider to adjust the synchronization delay (bridges short signal dropouts).
• Bookmark Tolerance: Slider to adjust the frequency matching tolerance for bookmarks.

Interaction & Performance

• Smart Analysis: The scanner uses Sparse Scanning (checking every 4th-8th bin) and accesses the core wf_data directly. This makes it highly CPU-efficient, especially on mobile devices.
• Virtual Scanning: The scanner “teleports” directly to signal peaks, eliminating the need for slow linear stepping and reducing network overhead.
• Squelch: By default, the scanner uses the current squelch level set by the slider in the OpenWebRX+ interface. This can be bypassed using the “Ignore Squelch” option in Width Filter mode.
• Hysteresis: Once a signal is locked, the squelch threshold is internally lowered by 2 dB to provide stable reception during signal fading.
• DC-Spike Protection: Technical interference at the center frequency (+/- 1.5 kHz) is automatically ignored to prevent the scanner from getting stuck.
• Manual Tuning: Clicking on the waterfall while scanning stops the scanner.
• Dynamic Step Size: The scanner automatically calculates the optimal jump distance based on twice the current filter bandwidth to ensure fast and reliable scanning.
• Modulation: The scanner is active for NFM, AM, FM, SAM, USB, LSB, and CW.
• Visualizer: Blocked ranges are shown as semi-transparent bars. High-performance rendering remains stable even when zooming deep into the spectrum (OpenWebRX+ offset-aware).

Configuration

No manual configuration in init.js is required. The plugin automatically adapts to the current profile, center frequency, and bandwidth.

License

MIT

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