The "carrier" that you hear on these signals is probably not carrier but
inband IM products from the low frequency audio signals. Listen closely
and you will see that it is only present with modulation.
It is not IM. An excellent discussion concerning the effect you're hearing
is well-documented on the NU9N web site. As audio approaches the carrier
set point in the lower audio octaves, to the ear it sounds like the presence
of a carrier, but disappears as you tune on-frequency. Somehow, all
unexplained things only in the presence of modulation tend to be blamed on
IM.
-Paul