First, make sure the PTT is working.
?- put qmx in digi mode, on vfo A
?- press the flrig PTT button, and see if a dot appears under the A while PTT is on
?- that means PTT is working
?- if not working, check the flrig config - PTT generic, and make sure "PTT on CAT Serial Port" is set to BOTH, with RTS and DTR OFF.
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Then make sure transmit audio level from PC is sufficient to drive the QMX:
?- set windows volume setting for the QMX playback device to 100%
?- in the FLdigi main window, bottom status border, near the right-hand-side, there is a "tx level attenuator" setting which by default is set to some number other than zero.? Set it fully up to 0.
?- in the FLdigi main window, top right, turn off both RxID and TxID.? Press 'Tune' there (with dummy load or matched antenna attached to QMX).? With that 'Tune' on, you should see first two dots appear under the A in the QMX display, then it should change to a line.? Two dots mean PTT worked and audio is being received by QMX, the line means that the audio is strong enough for digi mode transmit, and it should be transmitting full power.
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If you plan to run RTTY, make one more FLdigi setting change: Config -> Modem -> TTY -> Tx:? uncheck the "Shaped Tx" button, otherwise RTTY Tx will not work (external shaping interferes with QMX internal shaping).
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Now it should all work in digi mode for FSK types.? And you can also put it in SSB mode, and it will work on the other types.? But do the setup in digi mode, because it is easier to see that things are set up properly.? Digi mode is still preferred (will give better performance) for all single-tone-at-a-time modes (RTTY, MFSK*, etc), but SSB mode is required for all phase-shifting (PSK) or multitone types.