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fldigi - digital modem program for hamradio operators


fldigi [OPTIONS]


Fldigi is a cross-platform multi-modem program for most of the digital modes used by radio
amateurs today: CW, PSK, MFSK, MT-63, RTTY, Hellschreiber, DominoEX, Olivia, THOR and
Throb are all supported. It can also help calibrate a sound card to a time signal and do
on-air frequency measurement tests. Fldigi features basic rig control, logging, and
contest operation, “panoramic” PSK decoding, a PSK Reporter client, and remote control via


Long options begin with two hyphens and are handled by fldigi. The option names may be
abbreviated to any unambiguous substring, and the option argument may be separated from
the name by a space or equals sign, as per getopt(3).

Short options begin with a single hyphen and are passed directly to FLTK. They may be
abbreviated only as indicated.

--config-dir DIRECTORY
Look for and store configuration files in directory DIRECTORY, which is created if it
does not exist. Defaults to “$HOME/.fldigi”.

--rx-ipc-key KEY
Set the receive message queue key. May be given in hex if prefixed with “0x”. Defaults
to “9876” or “0x2694”.

--tx-ipc-key KEY
Set the transmit message queue key. May be given in hex if prefixed with “0x”.
Defaults to “6789” or “0x1a85”.

--arq-server-address HOSTNAME
Set the ARQ TCP server address. Defaults to “”. HOSTNAME may be any node
name string accepted by getaddrinfo(3).

--arq-server-port PORT
Set the ARQ TCP server port. Defaults to “7322”. PORT may be any service name string
accepted by getaddrinfo(3).

The --xmlrpc-* options are only available if fldigi was built with XML-RPC support.

--xmlrpc-server-address HOSTNAME
Set the XML-RPC server address. Defaults to “”.

--xmlrpc-server-port PORT
Set the XML-RPC server port. Defaults to “7362”.

--xmlrpc-allow REGEX
Allow only the methods whose names match REGEX. REGEX is a POSIX extended regular

--xmlrpc-deny REGEX
Allow only the methods whose names do not match REGEX.

List all available XML-RPC methods and exit. May be preceded by the --xmlrpc-allow or
--xmlrpc-deny options to verify their effect.

Perform the CPU speed test that is normally done when fldigi is run without an
existing configuration directory. Results are shown in the event log and options may
be changed to the recommended values for the measured CPU speed.

Unhide controls for adding noise to the transmitted signal.

Hide all main window widgets except the menu bar and waterfall (with its associated
controls). Meant to be used with external programs that control fldigi with XML-RPC.

--debug-level LEVEL
Set the event log verbosity. LEVEL is clamped to the range [0,5]; for Quiet, Error,
Warning, Info, Verbose and Debug. Defaults to “3” (Info).

Print version information and exit.

Print build information and exit.

Print options summary and exit.

Standard FLTK options
-bg, -background COLOUR
Set the background colour.

-bg2, -background2 COLOUR
Set the secondary (text) background colour.

-di, -display DISPLAY
Specifies the X server to connect to; see X(7).

-dn, -dnd or -nodn, -nodnd
Enable or disable drag and drop copy and paste in text fields.

-fg, -foreground COLOUR
Set the foreground colour.

-g, -geometry GEOMETRY
Set the initial window size and position. Fldigi may not honour this option.

-i, -iconic
Start fldigi in iconified state. Fldigi may not honour this option.

-k, -kbd or -nok, -nokbd
Enable or disable visible keyboard focus in non-text widgets.

-na, -name CLASSNAME
Set the window class. Defaults to “Fldigi”.

-ti, -title WINDOWTITLE
Set the window title. Defaults to “fldigi - <callsign>”.

Additional UI options
--font FONT[:SIZE]
Set the widget font and (optionally) size. Defaults to “sans:12”.

Options useful to developers
The --benchmark-* options are only enabled if fldigi was built (exclusively) for
benchmarking and batch decoding.

--benchmark-modem ID
Specify the modem. Defaults to “25” (“BPSK31”).

--benchmark-frequency FREQ
Set the modem frequency in Hz. Defaults to “1000”.

--benchmark-afc BOOLEAN
Enable or disable modem AFC. Defaults to “false”.

--benchmark-squelch BOOLEAN
Enable or disable modem squelch. Defaults to “false”.

--benchmark-squelch-level LEVEL
Set the modem squelch level (1—100%). Defaults to “0.0”.

--benchmark-input INPUT
Specify the input. Must be a positive integer indicating the number of samples of
silence to generate as the input, or, if fldigi was linked with libsndfile, the name
of the input audio file. The filename must contain non-digit characters.

--benchmark-output FILE
Specify the output data file. Non-textual output (i.e. Hellschreiber or MFSK images)
cannot be saved. Default: decoder output is discarded.

--benchmark-src-ratio RATIO
Specify the sample rate conversion ratio. Defaults to “1.0” (input is not resampled).

--benchmark-src-type TYPE
Set the sample rate conversion type. TYPE is an integer in the range [0,4]. Defaults
to “2” (“Fastest SINC Interpolator”).

The following options should not be relied upon. They are listed here only for the
sake of completeness, and may be replaced by GUI settings or removed altogether in a
future version.

--wfall-width WIDTH
Set the waterfall width.

--wfall-height HEIGHT
Set the waterfall height.

--window-width WIDTH
Set the minimum window width.

--window-height HEIGHT
Set the minimum window height.

--exit-after SECONDS
Run for approximately SECONDS seconds.

--frames-per-buffer FRAMES
Set frames per buffer option to FRAMES when creating PortAudio streams. Defaults to
“0” (let PortAudio choose).


Fldigi uses several environment variables, mainly set for child processes created by the
<EXEC> macro and the notifier.

General variables
The web browser to use for http and file URIs. Overrides $BROWSER and xdg-open(1).

Macro variables
The following variables are created in the environment of the child process that is forked
by the <EXEC> macro. They are empty if values are not available.

The receive message queue key.

The transmit message queue key.

The XML-RPC server address string.

The XML-RPC server port string.

The ARQ server address string.

The ARQ server port string.

The version string.

The process ID of the parent fldigi process.

The configuration directory.

The operator’s callsign.

The operator’s name.

The operator’s IARU (Maidenhead) locator.

The short modem name.

The long modem name.

The rig (radio) frequency.

The modem (audio) centre frequency.

The actual receive/transmit frequency, i.e. the sum of rig and modem frequencies
taking into account the rig sideband.

The text (frequency in MHz) contained in the QSO Freq log field.

The text (QSO start time) contained in the (time) On log field.

The text (QSO end time) contained in the (time) Off log field.

The text (other station’s callsign) contained in the Call log field.

The text (other station’s name) contained in the Name log field.

The text (received RST) contained in the (RST) In log field.

The text (sent RST) contained in the (RST) Out log field.

The text (other station’s QTH) contained in the QTH log field.

The text (other station’s Maidenhead locator) contained in the Loc log field.

The text (free-form notes) contained in the Notes log field.

The text (azimuth in degrees to other station) contained in the Az log field.

Notifier variables
The following variables are created in the environment of child processes created by the

These variables (i in [0,9]) contain substrings matched by capturing groups in the
event’s regular expression. 0 contains the whole matched text.

The number of substrings available.

Builtin event types that match callsigns will place the callsign in this variable.

The complete string that matched the event’s regular expression.

The modem frequency.

The event type.

The station’s country name (for events of type "station heard twice").

Debugging variables
The following variables are only used if fldigi was built with debugging support
(--enable-debug), or they are only useful when debugging specific modules.

If set, this variable disables glibc’s malloc debugging, which fldigi enables by
default when built for debugging.

Traces Fl::lock() calls.

Initialises hamlib in debug mode.


Fldigi is licensed under the GNU GPL, which grants you the right to run the program for
any purpose (freedom 0). However, permission to use it for the transmission of radio
signals can only be obtained from the communications authority of your country. When
given, this permission almost always comes in the form of an amateur radio license.

If you do not have an amateur radio license you can still have fun using fldigi as a
shortwave listener. One way to do so is by using the builtin PSK Reporter client to submit
realtime spots of transmitting stations; see RESOURCES below. All you need is a computer,
homebrew SDR receiver, and simple wire antenna!

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