It is shown that the presence of a gyrotropic plasma sheath covering a rectangular slot radiator may not alter significantly the radiation pattern when the static magnetic field is perpendicular to the slot. The plasma covered antenna remains omnidirectional and the radiated power is not significantly reduced when the cyclotron frequency

, the collision frequency

, and the operating frequency

, fulfill the inequality

. It is also found that the matching between the plasma covered antenna and its surrounding is sharply improved for certain combinations of the plasma sheath parameters and the operating frequency. This finding may have an application in plasma diagnostics, the slab width

and the plasma frequency

can be determined by varying

and

according to an expression derived in this paper.