Getting Started

This page describes how to launch the SimTX Transmitter, connect to a server and make a first transmission.

Requirements

• Java runtime (the transmitter is a Java desktop application).
• Network access to a SimTX server. The default server port is 5100.
• Optionally: audio files (wav, mp3, aiff, aif, au), an HTTP or HTTPS audio URL, a microphone, PipeWire (Linux system audio), or GNU Radio for IQ input.

Connecting to a server

When the application starts, a server selector dialog is shown before the main window.

1. Select a server from the list, or press Add Server... and enter a name, host, port (1 to 65535, default 5100) and an optional description.
2. Press Connect. The main window opens once the control connection is established.

If the control connection drops later, the client shows a reconnecting notice and retries every 3 seconds. The Disconnect button returns to the server selector.

First transmission

The default configuration is chosen to work immediately:

• Frequency 4625 kHz, power 100 W, modulation preselected with a 2700 Hz bandwidth.
• Antenna: End-fed half-wave (EFHW) with 49:1 transformer, 32.5 m wire at 10 m height. This antenna is close to resonance at 4625 kHz, which is why that frequency is the default. Changing the frequency far from resonance without changing the antenna produces a severe mismatch and very little radiated signal.

Steps:

1. Set a callsign in the Station section (default PA3NL) and click the world map to place the station, or type latitude and longitude directly.
2. In Transmission Source, keep the source type Audio File. Select Choose..., drag a supported file onto the window, or select URL... for an HTTP or HTTPS stream. Supported local formats are wav, mp3, aiff, aif, and au.
3. Press Start TX.
4. Watch the Radio Deck on the right. Before the server reports data it shows a local estimate; once telemetry arrives the header changes to measured output. The session also appears in the Active Sessions list.

If the server is full the session is queued and the list shows the queue position, see Sessions and Queueing.

Stopping

Select the session in Active Sessions and press Stop Selected, or press Stop All. Clear Finished removes completed entries from the list.

Saving the setup

The Presets menu stores the complete station configuration through Save Current Settings... and restores a file through Load Preset File.... The saved .stxpreset includes all fields, the source, and the antenna, including an imported NEC deck. This is distinct from the built-in Radio Presets, which only set the transmitter character.

Next steps

• Learn the full interface: Transmitter Interface
• Choose a better antenna for the target band: Antenna System
• Understand mismatch warnings: SWR and Transmitter Protection
• Browse shared presets and extensions: Extension catalog