  We study the spectrum and transmission coefficient of plane waves propagating
along square ribbons of varying widths, containing a square-shaped,
PT-symmetric impurity region. We start with a zero-width ribbon (1D chain) and
place a PT symmetric dimer. The spectrum is computed numerically and the
instability gain is computed as a function of the gain/loss dimer strength. The
transmission coefficient is obtained in closed form and examined as a function
of wavevector and the gain/loss parameter. Next, we study a ribbon in a narrow
ladder configuration containing a square PT impurity. As before, we compute the
instability gain numerically and the transmission coefficient in closed form
for the two possible input modes. Finally, we repeat the calculations for a
wider ladder ribbon containing a Lieb-like impurity in a PT configuration. For
all cases and transmission channels, we obtain transmission divergences in
wavevector-gain/loss parameter space, whose number increases with the width of
the ribbon
