Can't comment on the audio. It s been changed for V4. However if you expecting a lot of hiss
that not something it does. Hook it to an antenna and tune around to see. You should hear
an increase in noise just putting antenna on it and depending on the band, stations. The
receiver was designed to be quiet, that means low internally generated noise.
I think during the transmission tone there is a spot where you measure the frequency or compare it to
WWV at 10mhz.
Its not unique to V4. I suspect if you read around you answer is there.
Best I can do as I took a very different path to calibration.