SimTX Transmitter

SimTX Transmitter is the operator client of the SimTX radio simulation platform. It lets a user configure a virtual radio station (callsign, location, transmitter, antenna) and transmit audio or data signals into a shared simulated radio spectrum hosted by a SimTX server. Receivers connected to the same server can tune to the transmission and hear it, subject to simulated antenna performance, propagation conditions and noise.

The transmitter does not emit real radio frequency energy. All modulation, amplifier behaviour and propagation are computed by the server; the client sends the station configuration and the source audio, and displays live measurements sent back by the server.

Overview

A transmitter session works as follows:

1. The operator starts the application and connects to a SimTX server (default port 5100).
2. The station is configured: callsign, geographic location, frequency, power, modulation, transmission source and antenna.
3. The operator presses Start TX. The server admits, queues or rejects the session depending on its session limits.
4. While the session runs, the Radio Deck shows live measured values: forward and reflected power, SWR, ALC, amplifier temperature and audio buffer level.
5. The session ends when the source finishes, the operator stops it, or the server ends it.

Main topics

• Getting Started: installation, connecting to a server, first transmission
• Transmitter Interface: reference for every control in the application window
• Modulation Modes: supported modes and their bandwidths
• Transmission Sources: audio files, microphone, white noise, PipeWire, GNU Radio IQ
• Radio Presets: built-in transmitter characteristics, from clean lab exciters to overdriven CB rigs
• Advanced Transmitter Settings: the fifteen fine-tuning parameters
• Station Configuration: callsign, location and saving station presets
• Antenna System: how antennas behave and are configured, with a page per antenna type
• Antenna Calculations: resonant lengths, SWR, gain and loss arithmetic
• SWR and Transmitter Protection: what happens when the antenna is mismatched
• Power Amplifier Behaviour: heating, power foldback and permanent damage
• Sessions and Queueing: admission, queue positions, rejections and kicks
• Propagation Basics: what determines whether a signal is heard at a distance

What SimTX simulates

From the operator's point of view the simulation covers:

• Transmitter imperfections: compression, distortion, carrier leakage, hum, phase noise and more, selectable through Radio Presets or tuned individually.
• Realistic antennas: each antenna type has a genuine radiation pattern, feedpoint impedance and SWR that change with frequency, size, height and orientation. Custom antennas can be imported as NEC decks, see NEC File Import.
• Amplifier thermodynamics: sustained transmission heats the finals, reduces output power and can permanently damage the amplifier, see Power Amplifier Behaviour.
• Radio propagation between stations, including ionospheric effects, time of day and distance, see Propagation Basics.