Fldigi Users Manual  4.1.18

This software would not have been possible without the contribution of many programmers who have given their best to the open source community. The application is built upon the foundation of the Fast Light Tool Kit (http://www.fltk.org), a wonderfully fast and efficient graphical user interface design library. Many have asked what the Fast Light means. There are probably as many answers as there are programmers using the toolkit. I prefer to think of it as lightning fast and light on the code size. Take a look at the size of the executable for fldigi and then compare it with similar applications. I think you will be surprised by how small it is for what it does.

The active current development team consists of:

  • Dave Freese - W1HKJ
  • Stelios Bounanos - M0GLD
  • Remi Chateauneu - F4ECW
  • Leigh Klotz - WA5ZNU
  • Stéphane Fillod - F8CFE
  • John Douyere - VK2ETA
  • Joe Veldhuis - N8FQ
  • Chris Sylvain - KB3CS
  • Gary Robinson - WB8ROL
  • Stefan Fendt - DO2SMF
  • John Phelps - KL4YFD
  • Andrej Lajovic - S57LN
  • Robert Stiles - KK5VD

Localization files:

   Español    Spanish   Pavel Milanes Costa CO7WT
                        Christian W. Correa HK4QWC
   Deutsch    German    Marc Richter        DF2MR
   Français   French    Stéphane Fillod     F8CFE
   Italiano   Italian   Pierfrancesco Caci  IK5PVX
   Język      Polish    Roman Bagiński      SP4JEU
   Nederlands Dutch     Peter van der Post  PA1POS

Several authors have placed their digital modem code and signal processing code in the public domain and their source was either an inspiration or in some cases formed the backbone of the code used in Fldigi.

  • AE4JY - WinPsk - a windows application
  • Tomi Manninen, OH2BNS - gmfsk - a great digital modem program for Linux
  • Hamish Moffatt, VK3SB - dominoEX code originally for gmfsk
  • Dr. Steven W. Smith - author of "Digital Signal Processing", who has kindly placed an entire book on digital signal processing on the internet. (http://www.dspguide.com)

If you make a side-by-side comparison between gmfsk and fldigi source code you will see that they follow the same general structure. The primary difference is that gmfsk is written in the C language and uses the gnome/gtk libraries for the user interface. Fldigi is a C++ application that uses the Fast Light Tool Kit (Fltk) gui library. The design of Fldigi puts emphasis on separating the user interface from the sound card and transceiver input/output operations. Nearly all modern digital modem programs use a programming paradigm called "threads." Threads are light weight processes that share the same memory space, but each has its own stack. The use of threads makes the program look and feel responsive to the user while a lot of code is being executed in the background.

Many of the modem source code files are C to C++ rewrites from the gmfsk application. They say that copying is the best form of flattery and gmfsk simply had the best explanations and the easiest source code to read and understand. The author had also spent several months creating improvements and fixing bugs in the original gmfsk application. That exercise was the impetus to create Fldigi.

The Fast Fourier Transform used by Fldigi is a rewrite of John Green's public domain FFT code (FFT for RISC for MAC). The rewrite is in C++ and is implemented as a C++ template. Some of the signal processing algorithms used in Fldigi are from Dr. Smith's book. His on-line publication is sufficient to allow you to become fluent in FFT analysis and the creation of digital filters. I printed the relevant pdf files and then purchased the hard bound copy. Improvements to the original gmfsk signal processing algorithms can all be attributed to this excellent source.

And last but certainly not least, I must thank the crew who perform alpha testing and on-line support of the application. These are stalwart amateurs who risk their operating system and radio equipment in testing, testing and more testing. Their only reward is in being able to influence the design of the application and the fun of seeing it work and the bugs disappear. Thank you to:

Call Name Call Name Call Name Call Name
4Z5ST Boris K3GAU David KU1T Zibi VA3DB Dianne
AA0HW Chuck K4XTT Victor KV9U Rick VE3IXI Dave
AC7JN Dave K6KAR Kirk N0NB Nate VK2TMG Brett
CT1DRB David K7BRK Chris N2AMG Rick VK4BDJ David
CX7BF Walter K4RE Brian N4UM Tim W3NR Ed
DF4OR Ekki K9AO Rick N4ZNV Mike W4ROS Ross
DK1JBE Tom KB3FN Lynn N6WFL Jason W6JVE Jim
DL6XAZ Fred KD0AR Mike N8FQ Joe WA3VPZ Marshal
DL8FCL Walter KD4O Phil NN8B Don WA4SXZ Rich
G0UZP Paul KD8DKT Mike NT1G Skip WB8ROL Gary
G3TDJ Andy KE3Y Travis OZ4KK Erik WD4FDW Steve
G6CKR Roger KH6TY Skip PA0R Rein WD4FNY Bill
G8SQH David KL7NA Rob PA3GWH Richard WU9Q Bob

and many others whose names are not listed, please accept my apology.

The test team is representative of users on Windows, Linux, Free BSD and OS X operating systems. They have varying interests from very slow speed CW to high speed keyboard full break-in CW, from RTTY contesters to PSK rag chewers. They have insisted that fldigi perform well under all of those operations. I have been amazed by the global distribution of the testing team. It is easy to think that the internet will be the death of amateur radio. On the contrary it opens up so many additional ways for us to be cooperative.

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