Performance Tuning (No Code Changes)

If you are running on older hardware or a Raspberry Pi, the waterfall display can consume significant CPU. You can disable it without recompiling:

GUI Method: In the application menu, go to View and select Disable Spectrum & Waterfall.

Config File Method:

Close SDRTrunk.

Navigate to the SDRTrunk folder (often in your user home directory).

Open SDRTrunk.properties in a text editor.

Find or add the line: spectral.display.enabled=false.

Save and restart.

Advanced: Modifying Source Code

SDRTrunk is open-source software (GPL v3), meaning you can modify the Java code to add features or change behavior if the default settings are insufficient.

Source Code: Hosted on GitHub at DSheirer/sdrtrunk.

Build System: The project uses Gradle for building.

Requirements:

Java JDK: You will need a recent JDK (Check the repository README for the exact version, typically JDK 17 or 21+).

IDE: IntelliJ IDEA is highly recommended for working with the code.

Workflow:

Clone the repository: git clone https://github.com/DSheirer/sdrtrunk.git

Modify the code in src/main/java.

Rebuild the application using ./gradlew build (Linux/Mac) or gradlew.bat build (Windows).

Run your custom build from the build/install/sdr-trunk/bin directory.

Example Project: Disable Waterfall by Default

If you are building a custom version (e.g., for a headless Raspberry Pi image) and want the waterfall disabled by default for all new users, you can modify the default preference value in the code.

Locate the Preference:

Open the project in IntelliJ.

Search the codebase (Ctrl+Shift+F) for the string "spectral.display.enabled".

This string is the key used to store the setting. You will likely find it defined in a class like UserPreferences or a UI controller class.

Modify the Default:

Look for the line that retrieves this setting. It will often look like:
preferences.getBoolean("spectral.display.enabled", true);

The second argument (true) is the default value. Change this to false.

Recompile:

Run the build script (./gradlew build).

The resulting application will now default to "Waterfall Off" for any user who hasn't explicitly enabled it.