RTTY TX transmits Radio TeleTYpe (RTTY) signals using Baudot/ITA2 encoding. It generates an FSK signal with configurable baud rate, frequency shift, and tone placement.

Controls

Baud — Transmission speed. Options: 45, 45.45 (default), 50, 75, 100, 110, 150, 200 baud.

Shift — Frequency separation between Mark and Space tones. Options: 85, 170 (default), 200, 450, 850 Hz.

Inverted (checkbox, default: on) — Swaps Mark and Space tone assignments. Enabled by default to match the most common RTTY convention.

Mark t — Sets the absolute frequency offset of the Mark tone. Options:

Label	Meaning
CNT (default)	Centered: Mark = −shift/2, Space = +shift/2
0	Mark at 0 Hz offset
2125	Mark at +2125 Hz (US HF AFSK standard)
−2125	Mark at −2125 Hz
1275	Mark at +1275 Hz
−1275	Mark at −1275 Hz

The computed Mark and Space tone values (in Hz, relative to the carrier) are shown on the line below these controls. They update automatically when Shift, Mark t, or Inverted are changed.

Set message — Opens the text entry keyboard. The message text is displayed below the button. Default: PORTAPACK. The message is encoded using Baudot/ITA2 (USOS disabled for maximum receiver compatibility) and transmitted once per START press.

RF Parameters

Parameter	Value
Frequency	Stored in persistent memory — typical HF RTTY: 14.080 MHz (20 m)
Bandwidth	2.048 MHz
Sample rate	2.048 MSps
Stop bits	1.5 (fixed)
TX gain	0–47 dB (LNA), 0/14 dB (AMP)

Transmission

Press START to transmit. The message is sent once and transmission stops automatically when complete. Press STOP to abort early.

Settings Persistence

Settings are saved to tx_rtty.ini.