Getting Started

This guide takes a new user from downloading SimTX to sending an audio file. TX means transmit. All signals in this guide are simulated; a physical transmitter, antenna, or microphone is not required.

1. Download and open the transmitter

1. Open the official downloads page and download the latest SimTX transmitter JAR file.
2. Install Java 21 or newer for your operating system if it is not already installed. Eclipse Temurin provides Java downloads: choose version 21 or newer and the installer for your system. A Java installation with desktop support is required.
3. Keep the JAR in a folder where you can save files. The app keeps extension packages alongside the application by default.
4. Open the JAR. If double-clicking opens an archive program or does nothing, open a terminal in the folder containing the download and run the command below, using the actual downloaded filename.

java -jar simtx-transmitter-0.3.6.jar

The filename above is an example for version 0.3.6. Use the filename on the downloads page for a newer version. java -version shows which Java version the terminal is using. See startup troubleshooting if Java is missing or too old.

The app checks for updates before server selection. The steps and screenshots here describe the 0.3.6 interface.

2. Sign in and choose a server

1. In Connect your SimTX account, use Open browser and complete SimTX sign-in. If the browser asks for a code, enter the code shown by the app. Copy link lets you open the same sign-in page manually.
2. Approve the app in the browser, then return to the transmitter. The app continues when approval is received.
3. In Select SimTX Server, select a server and press Connect. The official server list supplies the address and port.

Your SimTX account is separate from a wiki editing account. Current transmitter versions do not require copying a Discord token into a Token field. If the app restores an existing sign-in, it can go directly to server selection.

Checkpoint: the main window is open and the Station section identifies the selected server. Use Disconnect to return to server selection. An unavailable server or failed sign-in is covered in Troubleshooting.

3. Enter a simple station setup

The left-hand side contains the setup. Scroll down inside it if the Antenna section or Start TX is below the window edge.

A prepared example in the 0.3.6 app. No server is connected in this illustration. In normal use, complete step 2 first.

1. Under Station, replace the example callsign with a name for your station. Click the map to choose the simulated station location, or enter latitude and longitude.
2. Under RF Signal, choose Generic HF transceiver and set Power (W) to 100.
3. Set Frequency (Hz) to 4625000. This is 4625 kHz, or 4.625 MHz. Enter the value in hertz, not 4625.
4. Choose AM Double Sideband Full Carrier and tick Auto beside Bandwidth. This selects a 10000 Hz bandwidth for ordinary AM audio. Leave the advanced transmitter settings closed.
5. Under Antenna, choose Dipole, set Wire Length (m) to 31, Height (m) to 10, Azimuth to 0, and Feedline Loss (dB) to 1.

This is a specific example for the frequency above, not a setting for every band. In the 0.3.6 local solver over average ground it gives an SWR estimate of about 1.26. Server conditions can change the result. Antenna System explains how to choose a different setup.

The application's original antenna default is a 32.5 m end-fed half-wave with a 49:1 transformer, at 10 m height. It remains available; the dipole example makes the first setup explicit instead of relying on a previous user's saved values.

4. Choose an audio file

1. Under Transmission Source, select Audio File.
2. Press Choose... and select a short audio file. WAV, MP3, AIFF, AIF, and AU are supported. A supported file can also be dragged onto the window.
3. Leave Audio Gain at 0.9. Leave Repeat off for the first test so the session ends when the file ends.

Checkpoint: the Audio File row shows the selected filename. A URL, microphone, or external signal generator is not needed for this test. Transmission Sources covers those alternatives.

5. Start and check the transmission

1. Press Start TX once.
2. Find the new row under Active Sessions. Running means it has started. Queued means it is waiting for capacity and will start automatically; do not keep pressing Start TX.
3. Select the running session. The Radio Deck displays server measurements when they arrive. FWD is outgoing power, SWR indicates antenna matching, and TEMP is the simulated amplifier temperature.
4. Press Listen to Own TX to check the selected signal before propagation. This tests the transmitted audio, not whether a distant listener can receive it.

To check reception elsewhere, use a receiver connected to the same server, tune to 4625 kHz, and select AM with a suitable bandwidth. Propagation Basics explains why a distant receiver may hear a weak signal even when the local monitor sounds clear.

If the session fails, read its error before changing settings. See Troubleshooting for silence, queueing, high SWR, and heat warnings. The default frequency is an example, not a reserved empty channel; choose another frequency and retune the antenna if needed for normal operation.

6. Stop and save

1. Select the session and press Stop Selected, or use Stop All to end all your sessions. A non-repeating file also finishes by itself.
2. Use Clear Finished to remove completed rows from the list.
3. Open Presets and choose Save Current Settings.... Save the .stxpreset file with a descriptive name.

Restore it later with Presets > Load Preset File.... Keep any referenced audio files available at their saved paths. This station preset saves the complete setup; Radio Preset only sets the simulated radio's power and character.

Continue from here

• Transmit a microphone or audio stream
• Save, load, and share station settings
• Choose AM, SSB, FM, or a data mode
• Change frequency and choose an antenna
• Install an extension or theme
• Look up any control · Browse every guide