This is indeed curious.? The QMX/QMX+ does have some birdies at specific frequencies, but these are only heard when tuning to the exact frequency.
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Your problem sounds like there is a self-oscillation present somewhere in the receiver chain for those two bands.? Check the band configuration screen for which LPF and BPF each of these bands uses, then inspect the windings and solder connections closely for the related toroids, and verify you put the correct capacitors in place.
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The I/Q plots sound fine - they do naturally degrade somewhat on the higher bands.? But as long as they are 90 degrees phase shifted, and both are of the approximate same magnitude and no significant DC offset, then they are good.? They also should have a reasonably large amplitude, e.g. +/- 30K or so, rather than some small numbers on the left axis.? Small numbers would indicate an attenuated input signal.? Different DC offsets indicate some other problem.
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