QMX?

[Mateusz K]

Hi,

QMX has I/Q samples mode when connected and appears in dmesg as

[  216.597569] usb 1-2: new full-speed USB device number 10 using xhci_hcd
[  216.736887] usb 1-2: New USB device found, idVendor=0483, idProduct=a34c, bcdDevice= 1.00
[  216.736900] usb 1-2: New USB device strings: Mfr=1, Product=2, SerialNumber=0
[  216.736903] usb 1-2: Product: QMX Transceiver
[  216.736907] usb 1-2: Manufacturer: QRP Labs
[  216.740388] cdc_acm 1-2:1.0: ttyACM0: USB ACM device
[  455.622510] usb 1-2: USB disconnect, device number 10

How to use GQRX with it to see the watefall ?

[Adrian Musceac]

Can you point out the relevant documentation that describes I/Q output mode?
All I could find in this document:
https://qrp-labs.com/images/qmx/manuals/operation_1_03_002.pdf
is that the USB UART is used for CAT control and configuration?

Adrian

[Mateusz K]

Hi Adrian,

Yes, the QMX USB interface handles both CAT control (e.g., for setting VFO via the serial port) and audio, it appears as a sound card in GNOME labeled "QMX Transceiver Digital Input (S/PDIF)" for input, with similar output.
From the operation manual (https://www.qrp-labs.com/images/qmx/manuals/operation_1_00_022.pdf): "When IQ mode is enabled, the raw I and Q channels from the ADC are fed to the USB soundcard directly, without any demodulation.."
There are YouTube demos like this one showing it with SDR++ (https://youtu.be/nUfEaWYVtek?t=13): connect via USB-C, use serial for CAT, and the built-in sound card streams I/Q.
For GQRX: First enable IQ mode via CAT commands, then select the QMX USB audio device as the SDR input. The format is 24-bit stereo at 48 kHz, with left/right channels carrying I and Q samples (per https://www.lloydm.net/Demos/QMX_Interface.html).
CAT commands are documented here https://qrp-labs.com/images/qmx/manuals/cat_1_02_006.pdf but a subset of Kenwood TS-480/TS-440.

QRPLabs QMX is quite a popular transceiver now and it would be very nice to be able to use it with GQRX for receiving and waterfall.

Regards,

Mateusz

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