Configuring

The first thing you should do is resize the main dialog and adjust the divider line between the Rx and Tx text widgets.  After resizing it should look like:

Font Selection

Before you start using fldigi you need to select the font that will be used in both the receive and transmit text windows.  From the Menu Configure/Defaults select the menu item Fonts.  A font selector dialog will open and you can select both the font type and size from this dialog.

Rig Control Configuration

Now pull down the Configure/Defaults menu and select the submenu Rig ctrl.  That will open up the rig control dialog tab on the main configuration dialog:

RigCAT Configuration

You will need to specify how your PTT will be triggered by the program including no ptt (none).  None would be appropriate if you are using the rig's VOX or an outboard sound card interface such as the SignalLink SL-1+ which produces its own VOX type of PTT.

You can use a serial port for control with the RTS and DTR pins configured for you particular interface.   The program allows you to use RTS, DTR or BOTH for the PTT signal.  The default is +V to enable the PTT line.  If your rig needs 0 V for the PTT enable, you can select the PTT reverse option.  The option  DTR=+V will cause the DTR to remain at +12 v at all times and the RTS should be selected as the PTT toggle.  This is compatible with the G3VGR interface.  If you use the RTS or DTR line on a serial port you can select TTY and fill in the port name as "/dev/ttyS0" for example.  Fldigi also recognizes the serial line naming convention used by MSDOS, COM1 ... COM4.  If you hold the mouse cursor over the entry widget for the serial port you will see a hint that specifies all of the discovered serial ports on your computer, including the USB serial ports.  The one shown above is for a rigCAT "rig.xml" file.  The rigCAT PTT command is being used for the PTT signal and the DTR pin on the serial port is being held high to power the CI-V interface.  The rig.xml file also specifies the DTR condition so in this case you would not have needed to check that item or specify the port.  

If you have hamlib installed and your transceiver accepts a PTT command string you can choose configure your rig for the hamlib library interface.  Select the tab Hamlib.  You may also use either RigCAT or Memmap rig control.  RigCAT requires you to use either a preconfigured rig.xml file associated with your transceiver or to write your own based on an existing file.  If you have either a Kachina or Argonaut and are using the CAT program from W1HKJ you can select Memmap.  The three sub tabs look like:



The Rig Control can be left blank or you can select Memmap, Hamlib or RigCAT.  If using Hamlib the Rig, Port and Baud Rate entries become active after checking the "use Hamlib" box.  The pull down selector for Rig: is populated by the hamlib library.  Select your rig from the list if you are using hamlib.  You must specify the serial port that hamlib will find the transceiver on in the Device field.  This must be a fully qualified device name as "/dev/ttyS1" for example.  If you hold the mouse cursor over the entry widget for the serial port you will see a hint that specifies all of the discovered serial ports on your computer, including the USB serial ports.  You also must select the baud rate that your transceiver interface is set for.

	You can suppress viewing signals below a particular frequency with the "Low Freq Cutoff" control.  This might prove useful under certain conditions. The waterfall palette or color scheme can be altered to suit your personal tastes and visual needs.  When fldigi is first started it creates a wide range of pre-built palettes in the $HOME/.fldigi folder.  The "Load" button gives you access to those palettes.  You may change any palette by clicking on the various color buttons beneath the palette sample.  A color picker opens for you to select the color by various means including specifying the RGB values.  If you create a palette that suits you better than any of the prebuilt ones you can "Save" the palette.  The file will be saved in the $HOME/.fldigi folder.
	The FFT Prefilter or window function is used to reduce aliasing in the FFT computation.  The default prefilter for the Fast Fourier Transform associated with the waterfall is Blackman.   You can try the other windowing filter.  Under some conditions you might prefer one of those.  The Blackman window has proven best for my setup.   Fldigi's waterfall FFT has a bin size of 1 Hz.  With an FFT of 8192 and a sampling rate of 8000 it takes almost a second to accumulate enough data to perform the full FFT.  A waterfall that dropped at one scan line per second would be hard on the viewer, so fldigi uses a first-in-first-out (FIFO) 8192 byte buffer for the FFT data.  512 byte audio blocks move through the buffer with each successive read of the sound card.  The full buffer of 8192 samples is used to compute the FFT.  That means that data in the FFT can have a latency of 8 scans.  This provides excellent frequency resolution but poor time resolution (the vertical waterfall appearance).  The latency control allows you to select the number of 512 byte blocks that are used for the FFT.  The default latency is set to 4.  You should be able to  achieve a reasonable compromise between the time and frequency domain resolutions. Your transmit audio signal can be viewed on the waterfall, the digiscope, the FFT display, and the oscilloscope display.  This is the audio signal being generated by the sound card.  It will be a representation of your transmited signal if and only if your transmit path is totally linear.   Please do not confuse this transmit signal view with what you are putting on the air.
	The waterfall cursor is a set of markers on the frequency scale that are spaced a signal bandwidth apart.  You can add a pair of lines that drop down from those two markers for the full height of the waterfall by selecting Cursor BW.  You can add a center line cursor to this pair of BW line by selecting Cursor Center.  You can also add a set of BW lines that straddle the received signal tracking point by selecting BW Tracks.  All three of these options are color selectable.  Click on the colored button to the left of the check box and a color selection dialog will open.

Sound Card Configuration

Next enter your personal information on the Operator tab of the configuration dialog.  This will be the information used by some of the macro expanders. You are now set to test the application.

The default modem is always Psk31.  Signals in this mode will appear as:


These are both very good signals, but the one on the left is showing some extra sidebands.  Notice how clean the signal on the right is.  Its IMD was running about -29 dB which is just about perfect for on the air signals.

Open the Psk modem configuration tab.  You can select this tab by menu item or you can short cut to this tab by right clicking the lower left status line item (it is a button that looks like a status message area).  This area reports your current mode.  Right clicking this box always opens up the configure tab for that modem (if available).


You should set the acquisition search range for waterfall left click action.  As you adjust this control you will see the red mode width change on the waterfall scale.  You can also adjust this value by pointing the mouse to the waterfall.  Hold down the Control key and rotate the mouse wheel.  The search routine which finds the psk signal operates on a s/n threshold detector as well as recognizing the Psk phase modulation.  You can adjust the acquisition signal to ratio threshold for the search routine.

The Psk Viewer adjustments are described here: Psk Viewer

If you operate fldigi as the modem for a PskMail Server you can specify that fldigi use the psk sweetspot and that its +/- automatic signal search range be limited by the number of Hertz entered in the Server Search Range control.

When it is working to your satisfaction and you can both receive and transmit signals, it is time to save the configuration.

Go to the Configure menu and select Save config or press the "Save Config" button on the configure dialog box.  The program will write the file ~/.fldigi/fldigi_def.xml.

Exit the program and restart it to test that your configuration was saved and is working correctly.

Your fldigi install is now ready for you to start receiving and transmitting digital signals.

Fldigi recognizes if any configuration changes are made and not saved.  You will then be prompted to save the configuration when exiting the program.

Miscellaneous Configuration

The sweet spot is the audio frequency at which your transceiver provides the best filtering for a particular signal type.  You can specify the value of the sweet spot for CW, RTTY and all others.  You can also elect to have the audio cursor placed at the sweet spot when changing modes.  The sweet spot is used for the QSY function.  

If your computer has a cpu clock speed that is less than 600 MHz you should check the "Slow cpu" setting.  This will adjust the waterfall and some signal decoding processing.  Performance will be somewhat reduced but still quite usable.