[hpsdr] PowerSDR mRX-FFT calibration issue v3.0.7

[dmb at lightstream.net]

Hardware: original TAPR Mercury/Penelope/Atlas combo, along with Metis

When I run the General > Calibration at 15 MHz against WWV, the resulting
calibration is about 9 Hz off, as determined both by my ears and the
Phase2 display when I adjust the main tuning for zero-beat in DSB mode.

Is there a way to further tweak this?

Thanks,
Dale WA8SRA