Transmitter Interface

This page is a reference for the SimTX Transmitter application window. The window is split into a configuration form on the left and a live monitoring area on the right, with a status bar at the bottom.

Server selector

Shown at startup and after a disconnect. It lists known servers with their details and provides:

• Add Server...: name, host, port (1 to 65535, default 5100), optional description.
• Connect: establishes the control connection and opens the main window.

If the connection to the server drops while the application is running, the title area indicates that the client is reconnecting and retries every 3 seconds.

Station section

• Server row with a Disconnect button (returns to the server selector).
• Callsign: station identifier shown to the server and other users. Persisted between runs.
• Location: a clickable world map that fills the Lat and Lon fields. Coordinates can also be typed directly. Persisted between runs.

RF Signal section

• Frequency (Hz): carrier frequency. Default 4625000 (4625 kHz), chosen to match the default antenna, see Getting Started.
• Power (W): requested transmitter output power. Default 100.
• Radio Preset: selects a transmitter character, see Radio Presets. Selecting a preset overwrites the power field and all advanced settings.
• Modulation: the modulation mode, see Modulation Modes.
• Bandwidth (Hz) with an Auto checkbox. Auto fills the typical bandwidth of the selected mode. Default 2700.
• Low-cut (Hz): audio low-frequency cutoff. Default 350. Editable only for modes where it applies.
• Show advanced transmitter settings: expands the fifteen fine-tuning fields, see Advanced Transmitter Settings.

Transmission Source section

• Source Type: see Transmission Sources.
• Audio Gain: input level, default 0.9.
• Microphone: device selector, visible only for the Microphone source.
• Tone (Hz): test tone frequency, default 1000. For the GNU Radio IQ source this field is relabelled IQ Port.
• Audio File row with Choose.... Audio files can also be dragged onto the window (wav, mp3, aiff, aif, au).

A hint line below the controls describes the currently selected source.

Antenna section

• Type: antenna selector, default EFHW + 49:1 unun. See Antenna System.
• Wire Length (m): main dimension of the antenna. The label adapts to the type (Circumference for the loop, Element Length for the vertical, Driven Element for the Yagis). A value of 0 means resonant length at the operating frequency.
• Height (m): feedpoint or apex height above ground. Default 10.
• Azimuth (°): orientation, 0 is north. Disabled for the vertical, which is omnidirectional.
• Feedline Loss (dB): fixed loss between transmitter and antenna.
• Import NEC... and Use built-in: load or clear a custom antenna geometry, see NEC File Import.

Start row

• Start TX: starts a transmission session with the current configuration.
• Save Preset... and Load Preset...: store or restore the complete station configuration as a .stxpreset file. This includes every field, the source selection and any imported NEC deck.

Radio Deck

The right-hand panel shows six meters:

Meter	Unit	Meaning
FWD	W	Forward output power
REF	W	Reflected power returning from the antenna
SWR	:1	Standing wave ratio at the transmitter
ALC	dB	Automatic level control action
TEMP	°C	Power amplifier finals temperature
BUF	s	Audio buffer fill

Before the server reports measurements the deck shows a local estimate computed from the antenna configuration. Once telemetry arrives the header switches to measured output. If the amplifier overheats the header shows a PA OVERHEATED warning, see Power Amplifier Behaviour.

Active Sessions

A list of the operator's sessions with id, callsign, frequency, modulation, power, status, source, SWR, bandwidth and server address. Buttons: Stop Selected, Stop All, Clear Finished. Session states are described in Sessions and Queueing.