I have had other receiver that did this (my R-75 does do it but it is
tolerable at this time) and I reduced this volume "resolution" issue by
adding an additional resistor in series with the top terminal of the
volume potentiometer. In several cases the resistor was the value of
the pot! This really increased the volume "resolution" on the low end.
I also have an FRG-100 and its audio control is just fine.

Frank
K3YAZ
Tucson