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EI4LF | Primers | QRPLabs QMX - Digi Modes

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QRPLabs QMX Digi-modes setup

This primer illustrates how to setup Digi-modes with a GNU/Linux computer using the WSJT-X Software.

1. GNU/Linux Modem Manager and Braille Services

Open a terminal on the GNU/Linux computer and insure that the Modem Manager and Braille Services are stopped.

Stop the ModemManager 

~$ sudo systemctl stop ModemManager
~$ sudo systemctl disable ModemManager
~$ sudo systemctl mask ModemManager

Stop the Braille service for access by sight impaired people.

~$ sudo systemctl stop brltty-udev.service
~$ sudo systemctl disable brltty-udev.service
~$ sudo systemctl mask brltty-udev.service
~$ sudo systemctl stop brltty.service
~$ sudo systemctl disable brltty.service
~$ sudo systemctl mask brltty.service

Connect QMX to GNU/Linux computer with a USB-USB cable and via the GNU/Linux terminal identify the devices created by the QMX.

~$ ls /dev/ttyACM*
/dev/ttyACM0

2. Time Sync the computer

A timesync either from a GPS receiver dongle of Network Time Protocol (NTP) server on the Internet is essential.

Check this:

~$ timedatectl status
                     Local time: Sat 2026-08-22 13:47:37 IST
                 Universal time: Sat 2026-08-22 12:47:37 UTC
                       RTC time: Sat 2026-08-22 12:47:37
                      Time zone: Europe/Dublin (IST, +0100)
      System clock synchronized: yes
                    NTP service: active
                RTC in local TZ: no

Install Chrony

chrony is a versatile implementation of the NTP. It can synchronise the system clock with NTP servers, reference clocks (e.g. GPS receiver), and manual input using wristwatch and keyboard. It can also operate as an NTPv4 (RFC 5905) server and peer to provide a time service to other computers in the network. It is designed to perform well in a wide range of conditions, including intermittent network connections, heavily congested networks, changing temperatures (ordinary computer clocks are sensitive to temperature), and systems that do not run continuously, or run on a virtual machine. Typical accuracy between two machines synchronised over the Internet is within a few milliseconds; on a LAN, accuracy is typically in tens of microseconds. With hardware timestamping, or a hardware reference clock, sub-microsecond accuracy may be possible.

Two programs are included in chrony, chronyd is a daemon that can be started at boot time and chronyc is a command-line interface program which can be used to monitor chronyd’s performance and to change various operating parameters whilst it is running.


~$sudo apt install chrony
~$ chronyc
chronyc> tracking
Reference ID    : BC7D4006 (t1.time.ir2.yahoo.com)
Stratum         : 3
Ref time (UTC)  : Sat Aug 22 12:58:48 2026
System time     : 0.000698347 seconds slow of NTP time
Last offset     : -0.001973122 seconds
RMS offset      : 0.054172028 seconds
Frequency       : 6.949 ppm slow
Residual freq   : -7.095 ppm
Skew            : 1000000.000 ppm
Root delay      : 0.051457714 seconds
Root dispersion : 16.224834442 seconds
Update interval : 64.3 seconds
Leap status     : Normal

This output indicates the clock is locked in and extremely accurate.

  • System time (0.000698347 seconds slow): Clock is less than 1 millisecond off from NTP time. FT8 only requires accuracy within 500 milliseconds (0.5 seconds), so it is well inside the acceptable threshold.
  • Stratum (3): The computer is synced to a highly reliable, low-level time server (Yahoo's NTP server).
  • Leap status (Normal): The NTP daemon is healthy, fully synchronised, and running without errors.

Install and setup WSJT-X

There are two configuration items to do on the WSJT-X software:

  • Choose the right USB Sound card, and
  • Set up the CAT communication so that WSJT-X can control the QMX via the serial comm port.

3. Setup the WSJT-X Software

Run WSJT-X

File >> Settings >> General Tab

  • My Call: <set operator Callsign>
  • My Grid: <set Maidenhead Location>
  • IARU Region: Region 1 (If in Europe, Africa, Middle East and Northern Asia)
  • Turn off the Map Grid Locator to US State and show US States in Messages with Grid.

File >> Settings >> Audio Tab

  • Soundcard Input (Receive): QMX USB Audio device
  • Soundcard Output (Transmit): QMX USB Audio device

File >> Settings >> Radio Tab

  • Rig: Select QRPLabs QMX
  • Serial Port: /dev/ttyCM0. (or whatever device was identified on the terminal above)
  • Baud Rate: 38400
  • Data Bits: 8, Stop Bits: 1, Handshake: None
  • PTT Method: CAT
  • Mode: Data/Pkt
  • Split Operation: Select Rig or Fake It (recommended for FT8)
  • Test: Click Test CAT (turns green)

4. TX Status

Set the WSJT-X power slider to the maximum setting.

Once the Transmissions are happening a Transmit Status indicator appears under the A to the left of the screen on the QMX.

  • Single dot (e): QMX has been put into transmit mode via an appropriate CAT command from WSJT-X, however it is not receiving any audio, so there is no RF output. The usual reason for this is that QMX has not been selected correctly as the output device in the WSJT-X audio settings screen.
  • Double dot (i): QMX has been put into transmit mode via an appropriate CAT command, and that it is receiving audio from the PC; however the audio level is too low, so there is no RF. Adjust audio level on the GNU/Linux operating system (see below).
  • Solid line (T): Everything is transmitting OK.

On the GNU/Linux computer adjust Audio Settings to 100% for the Analogue Output QMX Transciever.

5. FT8 QSO

A typical FT8 contact (QSO) follows a standard 6-step script:

  • Step 1 (Calling): CQ MW0UPH IO82 (Station calls CQ with their callsign and grid square)
  • Step 2 (Answer): MW0UPH EI4LF IO53 (You reply with your callsign and grid square)
  • Step 3 (Signal Report): EI4LF MW0UPH -11 (They send your signal report in dB)
  • Step 4 (Report Ack): MW0UPH EI4LF R-09 (You acknowledge their report and send theirs)
  • Step 5 (Final Ack): EI4LF MW0UPH RRR (or RR73 - They confirm receipt)
  • Step 6 (Sign-off): MW0UPH EI4LF 73 (You send sign-off wishes; QSO complete)

6. WSJT-X Dashboard

7. Monitor the log

~$ tail -f ~/.local/share/WSJT-X/wsjtx_log.adi
ADIF Export
<adif_ver:5>3.1.1
<created_timestamp:15>20260822 135633
<programid:6>WSJT-X
<programversion:5>3.0.2
<eoh>
<call:6>CT1DTM <gridsquare:0> <mode:3>FT8 <rst_sent:3>+06 <rst_rcvd:3>-11 
<qso_date:8>20260822 <time_on:6>145945 <qso_date_off:8>20260822
<time_off:6>150045 <band:3>20m <freq:9>14.075837
<station_callsign:5>EI4LF <my_gridsquare:6>IO53QU
<tx_pwr:2>5w <operator:5>EI4LF
<eor>

8. Use PSK Reporter

PSK reporter illustrates how far the signal is getting from the station and being received by automated listening stations.

9. Uploading to QRZ.com Log

Login to QRZ.com

My Logbook >> Settings >> ADIF Import/Export >> Import >> Choose File

Select the ~/.local/share/WSJT-X/wsjtx_log.adi file

Select Import ADI file.

Check within the QRZ.com logbook.




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