Level measuring device (5, 25), operating according to the pulsed radar principle, which is designed to measure a level of a medium in a vessel, with - a transmission unit with a pulse generation unit connected to a controller, -- wherein said transmission unit is designed to generate - according to predefined measuring cycles each comprising at least two measurements - a transmission signal (S n) consisting of microwave pulses of a predefined central frequency (f n) for the respective measurement, wherein the central frequencies (f n) of the transmission signals (S n) of at least two of the measurements are different from one another, - an antenna connected to the transmission unit, -- wherein said antenna transmits transmission signals (S n) into the vessel, and receives the signal parts reflected back in the vessel in the direction of the antenna as reception signals (R n) after a transit time (t) that depends on the distance of the corresponding reflector from the level measuring device (5, 25), -- wherein said antenna has a spatial radiation characteristic that is different for various central frequencies (f n) and depends on the central frequency (f n) of the transmission signals (S n), and -- wherein said antenna is a slotted waveguide antenna, which is designed in such a way that the radiation characteristic has two dominant main lobes, whose spatial orientation depends on the central frequency (f n) of the transmitted transmission signal (S n) and is different for different central frequencies (f n), and whose transmission directions to the two sides of the surface normal, which extends on the waveguide wall of the antenna into the vessel in the direction of the medium, each extend under the same angle to the surface normal which depends on the central frequency, and - a signal processing unit connected to the transmission unit and the antenna, -- wherein said signal processing unit receives the reception signals (R n) and evaluates them on the basis of the central frequencies (f n) of the microwave pulses of the associated transmission signals (S n) and the central frequency dependence of the spatial radiation characteristic of the antenna. - a transmission unit with a pulse generation unit connected to a controller, -- wherein said transmission unit is designed to generate - according to predefined measuring cycles each comprising at least two measurements - a transmission signal (S n) consisting of microwave pulses of a predefined central frequency (f n) for the respective measurement, wherein the central frequencies (f n) of the transmission signals (S n) of at least two of the measurements are different from one another, - an antenna connected to the transmission unit, -- wherein said antenna transmits transmission signals (S n) into the vessel, and receives the signal parts reflected back in the vessel in the direction of the antenna as reception signals (R n) after a transit time (t) that depends on the distance of the corresponding reflector from the level measuring device (5, 25), -- wherein said antenna has a spatial radiation characteristic that is different for various central frequencies (f n) and depends on the central frequency (f n) of the transmission signals (S n), and -- wherein said antenna is a slotted waveguide antenna, which is designed in such a way that the radiation characteristic has two dominant main lobes, whose spatial orientation depends on the central frequency (f n) of the transmitted transmission signal (S n) and is different for different central frequencies (f n), and whose transmission directions to the two sides of the surface normal, which extends on the waveguide wall of the antenna into the vessel in the direction of the medium, each extend under the same angle to the surface normal which depends on the central frequency, and -- wherein said antenna transmits transmission signals (S n) into the vessel, and receives the signal parts reflected back in the vessel in the direction of the antenna as reception signals (R n) after a transit time (t) that depends on the distance of the corresponding reflector from the level measuring device (5, 25), -- wherein said antenna has a spatial radiation characteristic that is different for various central frequencies (f n) and depends on the central frequency (f n) of the transmission signals (S n), and -- wherein said antenna is a slotted waveguide antenna, which is designed in such a way that the radiation characteristic has two dominant main lobes, whose spatial orientation depends on the central frequency (f n) of the transmitted transmission signal (S n) and is different for different central frequencies (f n), and whose transmission directions to the two sides of the surface normal, which extends on the waveguide wall of the antenna into the vessel in the direction of the medium, each extend under the same angle to the surface normal which depends on the central frequency, and - a signal processing unit connected to the transmission unit and the antenna, -- wherein said signal processing unit receives the reception signals (R n) and evaluates them on the basis of the central frequencies (f n) of the microwave pulses of the associated transmission signals (S n) and the central frequency dependence of the spatial radiation characteristic of the antenna.