fldigi and flmsg

Fldigi is a modem program for most of the digital modes used by radio amateurs today. It lets you connect your computer via sound (analog, what we can hear), over ham radio frequencies, to another computer. Flmsg is a companion program to manage forms of the kind used in Incident Command Systems, by the Red Cross, and other organizations.

Quickie Guide

v. 18-3

Klaus Berkner K6KHB

June 17, 2018

Download links: fldigiflmsg

(These are updated frequently, so check occasionally to assure you have the latest version).

This guide (v. 18-3) describes the configurations for fldigi 4.0.17 and flmsg 4.0.6

fldigi Practice Net

We have a practice net for using fldigi and its suite of apps.

We hope you can join us on Tuesdays, at 8:00 PM for the Contra Costa Digital Practice Net:

2 meters 147.060 /+ (100PL); linked with

224.780 MHz; PL 77.0 / 441.325+ PL 100.0

Also at 8:20 PM - 28.420 MHz

And at 8:40 PM - 3.593 MHz

Let’s start by opening fldigi.

The first time it is opened it will prompt you to fill in your call sign, etc.

Your locator is your Maidenhead grid square, CM87 for most of Martinez. (There is an App “Maidenhead” available to find your gridsquare.) [Here’s a site on the Internet too.]

If you want to check or edit the info, you can get back to this screen in fldigi by configure > UI > operator.

1. Set up the speaker and microphone:

configure > sound card > devices

Check the box “port audio”. In the “capture” and “playback” boxes, select the internal microphone and speaker if you will couple acoustically to your HT. (For more advanced use, if you use a SignalLink box, you would select the “USB Codec”). Save and close.

2. Select the digital signal mode:

Op Mode>MT63>MT63-2000L

fldigi is a versatile program that will encode/decode many different digital modes. In COMU/AEC we are using MT63-2000L (or MT63-2KL). [OpMode > MT6 3> MT63-2000L] Note that the box in the lower left corner of fldigi now reads MT63-2KL; it is a quick indicator of the mode that is being used. If the “RxID” and TxID” boxes in the upper right corner are checked green, fldigi will usually, but not always, automatically switch to the incoming mode. [We have found that RxID and TxID don’t work reliably when going through a repeater.] Once you get more proficient, you can try other modes.

3. Configure for MT63:

configure > operating > active modem 

on the upper bar select “Modems”; on the second bar select “MT63” check the box 8-bit extended characters (UTF-8). Save and close.

4. Set up waterfall:

The red bar in the waterfall area (black area at bottom of screen) should be between 500 and 2500 Hz, centered on 1500. If it isn’t, left click on the red bar at 1500 (or scoot the center white vertical bar to 1500). The waterfall of the incoming signal should fall between the red indicated at the top (The red bar will change for different modes).

5. Entering and sending a message:

Move cursor to blue screen and type the message. At the end of your message click the Rx>|| button just above the waterfall; this will automatically send a command to switch from transmit to receive at the end of the message. Now hit the T/R box in the lower right-hand corner. You will hear some acoustical signals and the message will move from the blue to the pink (or yellow) receive area, to show that it has been sent; the program then terminates the transmission and switches to the receive mode.

6. Squelch:

The SQL box in the lower right should be checked to turn on squelch. If it isn’t, the receive window will display garbage. Just to the right and above the SQL are two vertical bars. The right one is a slider to set the squelch level… left click and drag the horizontal bar to set the level. (Usually 2 or 3 mm from the bottom is sufficient.) The vertical box to the left of squelch will show a green bar when incoming signal is decoded; when it rises above the squelch level, text will appear in the receive box.

7. RxID and TxID:

On the right side of the top line in fldigi are boxes labeled RxID and TxID. When checked, the program will decode the header of an incoming message and adjust its settings to match the mode (e.g. MT63-2kl). So, if someone is sending in a different mode the program will decipher the signal. This is a handy feature when it works, however it usually doesn’t work when the radio signal goes through a repeater.

8. Set up for coupling flmsg to fldigi:

configure > miscellaneous > NBEMS

Chek the “enable”, “open with flmsg” and “open in browser” boxes. Click on the “locate flmsg“ box and find flmsg on your computer. When you click on flmsg, the address will be entered in the box. Save and close. (Note: In the future, after you install a newer version of flmsg, you have to return to this screen and update the flmsg version; ie. when you install flmsg 4.0.7, you will replace “flmsg-4.0.6” with “flmsg-4.0.7”.)

Set up the flmsg program

  1. When first opened it will pop up with a box asking call sign, etc. Fill this out. You can edit/change this in config > personal data.
  2. On the bottom of the screen, use the third box on the bottom (down-arrow), to select MT-63-2KL. (flmsg sometimes likes to default to domx22, so check this every time you open the program).

3. In the top bar of flmsg:

config > ARQ Interface

then select all the boxes except “Open Browser”

4. In flmsg:

config > User Interface

select “expert”

Using Forms

  1. Select the form you want to use: Click “Form” and select. There are two forms we commonly use for emergency communications: ICS -213 (form > ICS > 213) or spreadsheets saved as CSV files (form > CSV).
  2. select a form, ICS213 for a message
  3. Fill out the form.

To send a form: click AutoSend

  1. The program will ask with what name to save the message (it will suggest “your callsign-date-time-message number” as name, but you can change that to whatever you like)
  2. Click “save” at the bottom
  3. flmsg now transfers the message to fldigi, which will send the message. (you will hear the acoustical signal)

Receiving the message

On the receiving end fldigi will show the message in the receive window (yellow box), and, if everything is set up right, transfer the message to flmsg.

  1. If flmsg was not open, fldigi will open flmsg and the filled out form will “pop up” in the ICS-213 format (or spreadsheet).
  2. The message will also “pop up” in a beautifully formatted html file in your browser. This is particularly advantageous for longer forms (such as ICS-214, 202, 206) for which you must tab to see the various parts in flmsg format, but get the entire form in the HTML format.

Review old files

All messages are saved in either the “send” or “received” files. There are two ways to access those:

  1. In flmsg: file > open > NBEMS files > ICS or
  2. In fdigi: files > folders > NBEMS files > ICS
  3. Double click the file


  1. Locate the saved file, and drag it to the blue box in the upper right corner in flmsg [just below help]

Sending a saved file (Two options)

  1. flmsg: file > folders Locate the saved file, and drag it to the blue box in the upper right corner just below help
  2. flmsg: file > open

Create a template with basic info so you just have to add content [This is useful in a drill where you can prefill the incident name, your name/callsign/ and “This is a drill”

  1. Fill out a form that you want to use as a template
  2. to save it: Template > save as
  3. to load it: Template > load

There are some very useful guides on youtube. I like the ones by K4REF.

General: It’s ok to transmit digital on 2-m simplex, however the repeaters frown on it. For HF, the band plans have portions reserved for digital.

Troubleshooting: Common Problems

1) Soundcard: You set up the sound card as in step 1 above, but you either selected the wrong capture/playback devices, or the microphone (internal or external) is dead. You can check the microphone by tapping the case of your laptop and watching for activity on the waterfall display.

2) Noise cancellation software: Many modern operating systems have noise cancellation (or noise suppression) software which, when activated reject the digital signal as noise. The symptom is that you receive the beginning of a message, but after a few words you see nothing more (on the waterfall the signal starts out normal ad then disappears).

In Windows 10: sound control panel > recording; highlight the microphone and select properties; select enhancements and uncheck “noise suppression” and “acoustic echo cancellation”.

In Widows 7 go to control panel > hardware and sound > recording > microphone > properties and uncheck “noise suppression” and “acoustic echo cancellation”.

In Windows 10: type “sound” in the search box at the bottom of the desktop screen; click on sound – control panel; click on recording tab; highlight the microphone you are using; click properties > enhancements and uncheck “Noise Suppression” and “Acoustic Echo Cancellation”.

In MacOS 10.13: If there is a low demodulated signal (green bar) in fldigi: control panel > sound > input > use ambient noise reduction

3) In fldigi, you see activity on the waterfall as a message comes in, but there is no new information appearing on the yellow screen. Move the slider on the right side of the yellow receive box to the bottom to see the latest information coming in. (Sometimes the yellow display is “frozen” on some old message.)

4) Flmsg folder appears to have no content (or the content files are shaded) Sometimes, when you open a folder it may appear empty or the files that show are shaded. Whenever a folder is oped, Flmsg filters the display by the file extensions (.213, .214, .csv, etc). To see all files go to the “show” box at the bottom and scroll to “all files” Post script: It is a good practice to do a sound card calibration for your laptop. This can be done when you have some time at home.

The calibration program for Windows is at: http://www.k8jtk.org/drive/ham_radio/digital_modes/checksr/CheckSR.exe

Want a video overview? This one by Rick Frost K4REF is a good place to start.