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gMFSK v0.6 - The Gnome MFSK terminal program

gMFSK is a multi-mode soundcard terminal program for HF amateur
communications. Originally the program was written for compatibility with
the IZ8BLY Stream program in MFSK16 mode. Currently the program supports
the following amateur digital communications modes: MFSK16, MFSK8, RTTY,


The MFSK modem supports two modes:

 MFSK16	- 16 tones, 15.625 symbols per second
 MFSK8	- 32 tones, 7.8125 symbols per second

Both modes use convolutional encoding (R=1/2, K=7, NASA standard
polynomials) and viterbi decoding.

MFSK16 also supports sending small pictures in analog FM mode. This is
compatible with MixW ( Receiving pictures is
automatic. Sending is triggered with the macros $pic and $picc (see


RTTY support in gMFSK should be considered experimental. I have tried a
few decoding algorithms and the one currently in use is not necessarily
the best one.

All the parameters (shift, baudrate, number of bits, parity, number of
stopbits) are almost freely configurable. There is also a separate
"reverse" setting for RTTY which you probably want to enable if you want
to use USB to work RTTY.

The "MSB first" option is needed for the ASCII modes. Or at least when I
tested the modem against MMTTY ( it


Throb support is also to be considered experimental. There is a working
automatic sync method now but it may not be as good as it should be
(feedback welcome).

For more information about THROB please check Lionel's web page


PSK31 support in gMFSK borrows heavily from the C++ modem classes written
by Hansi Reiser DL9RDZ (which in turn is partly derived from the work of
Andrew Senior G0TJZ and Peter Martinez G3PLX). While I have not used any
code directly, much of the architecture and algorithms are almost directly
copied from there. As a result I think the PSK31 support is pretty mature.


The MT63 modem uses source code written by Pawel Jalocha SP9VRC. I have
only written a few lines of glue code to integrate Pawel's code to my
framework. The modem should be pretty mature. I haven't done much testing
but it does decode real life signals. There is no support for the IZ8BLY
style secondary channel. 8 bit characters are supported using the escape
127 encoding.


Both Feldhell RX and TX work now, but the mode still needs some work. The
AGC parameter adjustments don't work yet. Also TX uses antialiased fonts
which is probably not the optimal solution.


Operating gMFSK should be easy to learn even without much help if you have
any experience in operating with other modern soundcard digital modes. The
MFSK web site ( is suggested reading for
background information. Also the help in IZ8BLY Stream program could prove
useful. Note however that tuning in gMFSK works a little different to that
in Stream.

Setting audio levels is very important. The scope display should prove a
nice tool for setting the incoming audio level. However be aware that the
amplifier stages before the sound card mixer can also be overdriven
without showing signs on the scope display.

On transmit you should be just as careful. Overdriving MFSK or RTTY
doesn't produce intermodulation products as there is only one tone
transmitted at a time but harmonic products (of the audio) are always
present when overdriving. THROB, PSK and MT63 on the other hand do produce
intermodulation products if overdriven. FELDHELL produces key clicks is


The graphical user interface should for the most part be self explanatory.
From top to bottom there are the Menubar, Toolbar, QSO data area, Received
text, Transmitted text, Preconfigured messages buttons and the Waterfall
indicator area. In addition to the obvious there are a few additional

As with any Gnome application the Menubar and Toolbar areas are dockable,
ie. you can drag them around the desktop or the application window.

The received text and the QSO data area are of course subject to the
normal X Window Selection system: dragging with the left button selects
text and the middle button pastes the selected text. However the received
text area also implements an additional trick with the right button.
Clicking the right button over a word selects the word and opens a context
menu where you can select where you want the selected data to be pasted.

The waterfall can be paused from the popup menu that opens if you right
click over it. The waterfall config dialog can also be activated from the
popup menu.

The status bar shows modem state, transmission mode and UTC time. Clicking
the mode label is a shortcut to the mode config dialog.

The "Log entry" button sends the QSO data to logging program using inter
process communication (IPC). Currently only xlog
( supports this feature.

The "New entry" button clears all the QSO data fields and resets the QSO
time (the first change after a reset on any of the QSO data fields sets
the time).

The most used functions now have keyboard accelerators. Fixtext buttons
show the associated function keys in their labels and the other buttons
tell you the accelerator in their tooltips ie. when you hover the mouse
pointer above the button (be sure to enable tooltips in gnome config).

All in all, I recommend experimenting with the GUI before having real


The predefined text buttons can contain macros. Macros start with the
letter $. A standard macro is of the form $text. A list of available
standard macros is here:

  $$		- The letter '$'
  $tx		- Push the TX button.
  $rx		- Push the RX button.
  $pause	- Push the Pause button.
  $abort	- Push the Abort button (this is probably of no use to anyone).
  $mycall	- Callsign as defined in preferences.
  $myname	- Name as defined in preferences.
  $myqth	- QTH as defined in preferences.
  $myloc  	- Locator as defined in preferences.
  $myemail	- Email address as defined in preferences.
  $time		- Local time.
  $utctime	- Universal Coordinated Time.
  $date		- Local date.
  $utcdate	- UTC date.
  $call		- Other partys callsign taken from QSO data.
  $band		- Band taken from QSO data.
  $rxrst	- Received RST taken from QSO data.
  $txrst	- Transmitted RST taken from QSO data.
  $name		- Other partys name taken from QSO data.
  $qth		- Other partys QTH taken from QSO data.
  $notes	- Notes taken from QSO data.
  $soft		- Software version.
  $mode		- Currently active mode name.
  $pic		- Grayscale picture
  $picc		- Color picture

The macro name can also be enclosed in curly braces. This can be useful if
you need to avoid any spaces between the macro and some text. The macro
can also have an optional argument separated by a colon. This only works
in conjunction with curly braces. Currently this argument is only useful
with the picture macros where you can supply a filename that way. A
typical picture macro might be:


In addition to standard macros you can use so called command substitution
with a macro of the form $(command). The command is executed using
fork()/exec() and the standard output of the command is captured (standard
error is discarded). If the last character of the captured output is a
newline, it is removed.

The macros are evaluated at the time the button is pressed (as opposed to
being evaluated during the transmission) which is a significant fact
especially with the "push ... button" and date/time macros.

An unrecognized $-macro is ignored.


This program is something I wrote for my own amusement. I'm not a
professional DSP engineer (though I may want to be one in the future) and
I'm certainly not a GUI programmer nor do I ever want to be one.
Suggestions especially for the GUI part are more than welcome!

Hopefully the program is of use to you!


Thanks to Murray ZL1BPU and Nino IZ8BLY for creating a very cool ham
communication modes, MFSK16 and MFSK8. Special thanks to Murray for the
technical documentation of MFSK16/8 and Hellschreiber.

Thanks also to Jesús EB1DIX for his RTTY decoder program for Linux. I used
that software as the base for my experiments and a lot of ideas was
borrowed from it.

Likewise thanks to Lionel G3PPT for making Throb source code publically
available. Again lot was learned just by browsing through it.

Thanks to Hansi DL9RDZ for his PSK31 C++ classes and the work of Andrew
G0TJZ and Peter G3PLX on which the classes are based on.

Special thanks to Pawel SP9VRC for his work on MT63 and the source code
for it. Due to a stupid oversight from my part I released gMFSK v0.5 with
Pawel's MT63 code under GPL even though Pawel's original license was not
GPL-compatible. Fortunately Pawel has since agreed to release his code
under the GPL. Thanks Pawel!

Also many thanks to Phil KA9Q and Charles G4GUO for giving ideas and/or
code for the project. Neither probably knew about this project but that's
simply what free software is, everyone benefits from it!

Last but not least many thanks to Joni OH2NJR/OH2MUI for providing me with
feedback and equipment to be able to develop and test the stuff.....

Tomi Manninen, OH2BNS <>
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