Troubleshooting

Follow the checks for the visible symptom. Change one setting at a time and test again. Getting Started supplies a complete example to compare against.

The application will not open

1. Run java -version in a terminal. The transmitter requires Java 21 or newer with desktop support.
2. Open a terminal in the download folder and run java -jar followed by the actual JAR filename. This shows errors that may be hidden when double-clicking.
3. If the file opens as an archive, use the command above instead of extracting it. If Java reports an unsupported class version, check that the terminal is using the newer Java installation.
4. Download a fresh copy from the official downloads page if the file is incomplete.

Sign-in does not finish

1. Keep the transmitter sign-in window open and finish approval in the browser.
2. If the browser did not open, use Open browser or Copy link. Enter the displayed code only if asked.
3. If authorization expires, use Try again to obtain a new sign-in attempt.
4. Check network access to SimTX. A wiki account does not sign the transmitter into a SimTX account.

No server is available, or the connection drops

Retry in a moment, or select another available server.

The app automatically tries to reconnect if the connection drops. Session Auto-reconnect is a separate setting: it restarts an interrupted transmission after a connection error. See Sessions and Queueing.

Start TX fails

1. Read the displayed failure reason. Account limits, invalid fields, and missing files need different fixes.
2. Check that the frequency is entered in hertz and that numeric values are valid.
3. For Audio File, select a supported file with Choose.... For a Lua mode, select every required input shown below its controls.
4. For GNU Radio IQ, check its local TCP connection and sample format. See Transmission Sources.

The session is queued

Wait for a slot, or stop the queued session if it is no longer wanted. Queueing is not an audio error. Repeatedly pressing Start TX creates more requests. A rejection or account-limit message must be resolved separately.

The session runs but there is no sound

1. Select the running row and use Listen to Own TX. Check the computer's output volume and device.
2. Confirm that the selected file or microphone contains audio and Audio Gain is not zero. An ended file is marked Finished; use Repeat only when looping is intended.
3. A URL must provide supported audio, not merely a webpage containing a player. Try a local file to isolate a stream problem.
4. If the local monitor works but a remote receiver does not, check the receiver's server, frequency, mode, and bandwidth. Then check distance, antenna direction, and propagation.

The sound is distorted

Reduce Audio Gain or final drive. Compare with a clean radio preset, noting that changing the radio preset also changes requested power and advanced settings. Check AM index and compressor settings if they were changed. Increasing RF power does not repair distorted source audio.

SWR is high or output power is low

1. Check whether the deck is showing a local estimate or a selected session's measurement.
2. Verify antenna type, length, height, and frequency together. Changing frequency can detune a previously working antenna.
3. For a dipole, start near 143 / frequency in MHz metres and adjust length while watching the estimate. Length zero selects a nominal template, not a guarantee of SWR 1.
4. Check the TEMP meter as well. Mismatch and overheating can both reduce output power.

See SWR and Transmitter Protection and Antenna System for the full explanation.

The amplifier overheats

Stop the session or reduce power and drive. Long steady signals generate more heat than intermittent speech. Protection reduces power automatically; severe heating can damage the simulated amplifier for that session. See Power Amplifier Behaviour for thresholds and recovery behavior.

An extension is missing or does not work

1. Open Extensions > Problems and read the package-specific error.
2. Check that required library packages are installed and compatible. The catalog can offer missing dependencies.
3. After a local edit, select Reload now. Check the manifest types and entry filename if developing a package.
4. An audio add-on must be enabled in Add-ons and used with a supported mono-audio path. It does not process direct IQ, white noise, or PipeWire Stereo.

For installation steps see Lua extensions; for publication and updates see Extension catalog.

Ask for help

On SimTX Discord, include the app version, operating system, server name, exact error, and the steps that reproduce it. A screenshot of the relevant controls is useful. Do not include sign-in codes or credentials.