pirtty: RTTY

Sends a text message as RTTY: Baudot code at 45.45 baud, with two tones 170 Hz apart. Receive it in USB mode with any RTTY decoder. Code: pirtty.go.

Fields

JSON	Go field	Type	Required	Rules
frequency	Frequency	float64	yes	Hz, 5000 to 1500000000
spaceFrequency	SpaceFrequency	*int	no	Space tone in Hz, greater than 0; gorpitx sends 170 when it is not set
message	Message	string	yes	Not empty or only spaces

The program puts the mark tone at spaceFrequency + 170, so the shift is always the standard 170 Hz. The tones sit above the carrier frequency, like audio fed to an SSB transmitter. With the default space tone of 170 Hz the mark is at 340 Hz; decoders usually expect something like 2125/2295 Hz or 1275/1445 Hz, so set spaceFrequency to match your decoder.

Baudot has letters and figures shifts; the program inserts them as the text switches between letters and digits or punctuation. Lowercase letters go out as uppercase.

Example

{
  "frequency": 14080000,
  "spaceFrequency": 2125,
  "message": "RYRYRY DE N0CALL"
}

Runs:

stdbuf -oL "$GORPITX_PATH/pirtty" 14080000 2125 "RYRYRY DE N0CALL"

The arguments are positional: frequency, space tone, message. Without spaceFrequency the second argument is 170.