2.7.6 Digital - Fldigi for Sound Card Modes

1. The Fldigi interface

The Fldigi sound card interface is based on the fldigi code by Dave Freese, W1HKJ.

Fldigi supports a wide variety of digital modes, including not only AFSK RTTY and PSK, but also other less common modes such as MFSK, MT63, Olivia, Throb, etc.

Fldigi is a stand alone application, so you can also use it separately from N1MM Logger. Note that the configurations for Fldigi stand-alone and within the Logger are separate, i.e. changes made to the stand-alone configuration will not be applied to the configuration within the Logger, and vice versa.

Fldigi does not support keying outputs on serial or parallel ports, as used by N1MM Logger for CW and FSK keying. Fldigi can be used from the Logger for AFSK RTTY or for PSK31 or other digital modes, but not for transmitting RTTY using FSK unless you use an external hardware circuit to convert audio output from Fldigi to an on-off keying signal for FSK. It can also be used as a CW receive-only decoder, but not for transmitting CW. For transmitting CW, use one of the CW interfacing methods detailed in the "Basic Interfacing - Radio, CW, PTT" chapter. You must not check the Digital check box on a port that will be used for CW keying while the DI window or the CW Reader window is open.

2. Download and Configure Fldigi

2.1. Download Fldigi

  • Download the current release of fldigi from the W1HKJ website at http://www.w1hkj.com/ . You can find a copy of the full installer for the current version of fldigi at that website. This file is a self-extracting executable, similar to the N1MM Logger installer. Download the installer file to a temporary folder and then execute it. It is recommended that you install fldigi in its own program folder and not in the N1MM Logger+ program folder. By default, the installer will install fldigi to C:\Program Files\Fldigi-x.xx.xx\, where x.xx.xx is the fldigi version number.
  • If you are using Windows Vista, 7, 8 or 10, and you want to run fldigi from inside N1MM Logger+, you must use a copy of fldigi.exe that is located in its own folder outside the Program Files (or Program Files(x86)) folder. You can, for example, create a folder for fldigi inside your N1MM Logger+ user files area, then make a copy of fldigi.exe from the original installation location and copy it into the new folder. The only file you need to copy is the exe file; it will create whatever other files it needs the first time it is run.

2.2. Fldigi Initial Configuration

After fldigi has been downloaded and installed, open the Configurer and set up the path to fldigi.exe under the Digital Modes tab. After closing the Configurer, choose a contest in N1MM Logger that supports digital modes, select the Logger's Window > Digital Interface menu item, and then in the Digital Interface window, select the Interface > Fldigi menu item.

When you first open the fldigi interface from the Logger, and also any time you install fldigi into a different location, such as separate locations for the two digital interface windows or for the DI window and the CW Reader window, you will be prompted to fill in some configuration information by the fldigi configuration wizard, as follows:

  • Operator information - You do not need to fill in any of this information; N1MM Logger+ handles logging and all related information
  • Audio devices - Under the Devices tab, check the PortAudio box and select the sound card input and output you are using for Capture and Playback. Click Next
  • Transceiver control - Select the XML-RPC tab, check the Use XML-RPC Program box, and click the Initialize button. Do NOT select RigCAT, Hamlib, or MemMap for rig control; none of those will work with N1MM Logger+
  • You can let N1MM Logger handle PTT, in which case you do not need to configure PTT in fldigi. This is the simplest (recommended) configuration. However, if you do not use PTT in other modes and you want to use hardware PTT controlled by fldigi, you can select the Hardware PTT tab, check the Use separate serial port PTT checkbox, select the appropriate COM port in the Device: window, and check either Use RTS or Use DTR, depending on which one your hardware setup uses. If the label on the Initialize button is red, click on the button. Note that a COM port that is used by fldigi cannot be used simultaneously by the Logger for other purposes. If you are time-sharing a serial port between fldigi in digital modes (not including CW) and the Logger in CW or SSB, check the Digital check box beside the COM port in the Configurer to ensure that the Logger will not try to use this port while the Digital Interface is open
    • If you intend to use fldigi as a receive-only CW decoder, be aware that you cannot use fldigi to transmit CW. Also, you cannot control PTT from fldigi on the same port that N1MM Logger+ uses for CW keying; do not check the Digital check box beside this port, and do not configure it within fldigi as a PTT port
  • Click Finish

The fldigi configuration wizard does not automatically save its settings. After you have exited the configuration wizard and the main fldigi interface window has opened, you must save the configuration settings using the fldigi Configure > Save Config menu item. If you don't do this, then every time you open the fldigi window you will have to go through the configuration wizard steps again. Similarly, any time you make a subsequent change to the fldigi configuration you must explicitly save the new configuration if you want the change to be remembered.

Newer versions of fldigi may default to requiring confirmation from the user before you shut them down. If that shutdown is initiated by shutting down N1MM Logger+, instead of by shutting down the DI windows and engines first, this can result in fldigi continuing to run after the Logger has shut down. This will cause problems the next time you start up the Logger. To prevent this from happening, you need to make a change in the fldigi configuration file. In each folder that fldigi is run from, find the file called fldigi_def.xml. (Note: this file is created the first time fldigi is run from this location, i.e. it will not exist until after you have run that copy of fldigi at least once). Right-click on the file name, select Open with... and then select Notepad or Wordpad as the program to open the file with. Look for a line that reads <CONFIRMEXIT>0</CONFIRMEXIT> or <CONFIRMEXIT>1</CONFIRMEXIT>. If you see a 1 between the two keywords, change it to a 0 and save the file. Repeat this for each and every copy of fldigi you use from within N1MM Logger+ (DI1, DI2, additional RX-only digital windows, CW Reader 1 and/or CW Reader 2).

3. The Fldigi Interface Window

Fldigi Waterfall

  • Menu
    • File
      • Exit - closes the Fldigi window
    • Op Mode
      • CW - This configures Fldigi to decode CW (receive-only)
      • PSK - select BPSK-31 for normal PSK31, BPSK-63 for PSK63, etc.
      • RTTY - select RTTY-45 for normal 45 baud AFSK RTTY
      • Other selections can be used for other modes - see the fldigi help for details
    • Configure
      • Waterfall - under the Display tab, you can select whether to show audio or RF frequencies in the scale at the top of the waterfall, and whether to display transmitted as well as received signals
      • Rig control - XML-RPC should have been selected during the initial configuration. You can use the Hardware PTT tab to change the PTT settings for a separate hardware PTT port
      • Sound card - you can select the sound card to be used by Fldigi under the Devices tab
      • Modems - this is where you make configuration changes that apply to specific modes only (e.g. PSK-specific changes, or RTTY-specific changes)
      • Save Config - use this to save the new configuration any time you make changes
    • View
      • PSK Browser - opens a browser window that can display up to 30 signals within the waterfall simultaneously (PSK only). To configure this browser window, use Fldigi's Configure > Modems > PSK > Viewer configuration window to set the number of channels, the starting (lowest) audio frequency (channel separation is 100 Hz), and various other parameters

Most Fldigi menu items not mentioned above are either not used by N1MM Logger, or perform advanced functions that are not needed for basic operation. See the fldigi help at the W1HKJ web site for more details (there is a link to the Fldigi-Help page from the download page at

Note also that when the Fldigi engine is selected, additional buttons appear in the Logger's Digital Interface window:

  • Align - for retuning the radio so that the desired signal is aligned on a pre-configured frequency
  • Lock - to lock the transmit frequency at the present position in the waterfall while allowing the receive frequency to vary (for operating split)
  • Rev - in sideband-sensitive modes like RTTY, reverses the tones
    • Unlike the other digital engines used in the Logger, Fldigi assumes the rig will be in USB for RTTY. If you are using LSB, you will need to use the Rev button to tell Fldigi to reverse the tones. If you have tuned in a signal but all you see in the receive text window is garble, try clicking the Rev button once or in some cases, twice (sometimes you may find it necessary to toggle the Rev state off and back on to get it to "take")

Note that older versions of Fldigi only use the left channel on input; for that reason, in most SO2V installations these older versions of Fldigi can only be used from Entry Window 1. Starting with Fldigi version 3.22.06, Fldigi is now capable of using either sound card channel for input. In any copy of Fldigi that you want to use with the right channel of the sound card, use the Configure > Sound Card menu item in the Fldigi window to open the Fldigi configuration window. Select the Right channel tab, and near the bottom under Receive Usage, check the Reverse Left/Right channels check box to switch Fldigi to use the right channel on RX. Click on Save to save the configuration change, and then close the configuration window.

Last Modification: 07 May 2018 23:08:40 EDT by VE3KI.