  We study CPT- and Lorentz-odd electrodynamics described by the Standard Model
Extension. Its radiation is confined to the geometry of hollow conductor
waveguide, open along $z$. In a special class of reference frames, with
vanishing both 0-th and $z$ components of the background field, $(k_{\rm
AF})^\mu$, we realize a number of {\em huge and macroscopically detectable}
effects on the confined waves spectra, compared to standard results.
Particularly, if $(k_{\rm AF})^\mu$ points along $x$ (or $y$) direction only
transverse electric modes, with $E_z=0$, should be observed propagating
throughout the guide, while all the transverse magnetic, $B_z=0$, are absent.
Such a strong mode suppression makes waveguides quite suitable to probe these
symmetry violations using a simple and easily reproducible apparatus.
