No, Mike, you don't want to do that, unless you also want to run the QMX at that lower voltage.
This is because the calibration routines store the phase compensation values for voltages across the full modulation range - and you don't want the high voltage ones to be empty, since it may cause distortion when those voltages are used in operation.? So you want to run the calibration at the highest source voltage that you will run your QMX in operation.
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Note that the majority of QMX/QMX+ devices have no problems with the calibration.? I have 2 QMX and 2 QMX+, on which I have run the calibration many times without any issues.? [I ran them many times during the beta period, due to updates and working around early calibration problems.]? So the odds are in your favor.
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But for some as-of-yet-unknown reason, there is something about certain QMX/QMX+ builds/units that makes them sensitive to the calibration procedure, and the finals and sometimes the PA voltage modulation transistor Q507 burn out.? Hans already made several changes in the firmware to reduce the chance of it happening, but for some reason on a select few QMX* it still happens.? Some conjecture that it is because of already-weakened finals, an already-failed Q507 (but in the release code Hans put in a check for that one), voltage spikes from L502, a poor connection to the dummy load, or other build-related issues - but nobody really knows.
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So if you definitely do not want to take any chance of breaking your QMX*, don't do the calibration.? The SSB performance of QMX* will still be very good. ? If you have a greater risk tolerance, and are willing to change the very inexpensive PA transistors if they do blow, then certainly do the calibration and enjoy the 'better SSB performance' that is promised.
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Stan KC7XE
