  Deshpande and Rankin (DR1999, DR2001) claim that the frequency of the very
narrow feature, in the spectrum of radio flux variations of PSR B0943+10, is an
alias of its actual value. For this, they need to interpret the narrow feature
as a very stable pattern of drifting sub pulses on the polar cap of this
pulsar, within the framework of the Ruderman and Sutherland (1975) model. This
paper discusses several factors within the same framework, that may perturb a
very steady pattern of drifting sub pulses, leading to a broadening of the
spectral feature. One should be cautious in (1) identifying such very narrow
spectral features with a very stable pattern of drifting sub pulses, and (2)
use this picture to resolve the issue of aliasing in PSR B0943+10.
