Mechanical antennas with rotating permanent magnets are a relatively new type of transmitting antenna in low- and ultralow-frequency (LF/ULF) ranges. The perspectives of the applications are encouraging, especially in the field of non-destructive defectoscopy and communications through conductive media (underwater communications), which is reflected in the articles published in the last decade. This article describes the experimental setup, results, harmonic analysis, and simulation validation for two configurations of mechanical antennas with rotating NdFeB permanent magnets. The emphasis is placed on the known analytical equations, specifically on the matching of the measurement results with the analytical data as well as with the results given by the numerical analysis. Also, several means of measurement are used to validate the results through replicate testing. Through analytical analysis and the performed measurement, this article establishes the basics for designing mechanical antennas with rotating permanent magnets for the considered configurations based on a single static magnetic field measurement. Finally, we explore prospects for future research in this domain as well as the advantages and disadvantages compared to other types of LF/ULF antennas.

The paper presents the construction of piezoelectric accelerometers, the mechano-electrical transfer mode, typical constructions, basic characteristics, and theoretical approaches to the vibration phenomenon appearing in accelerometry and calculation possibilities of the various characteristics of the transducers. In the second part of the paper, the functional testing of such a transducer is also presented, piezoelectric vibration transducers being useful for vibration determination and dynamic balancing of electric machines. In general, vibration transducers provide, through mechano-electrical conversion according to different principles, an electrical signal directly proportional to a vibration parameter (acceleration, travel speed, amplitude); depending on the principle, they can be piezoelectric, electrodynamic, inductive, capacitive, resistive or based on the Hall effect, with magnetic fluids, interferometric, laser, servo-accelerometers, etc. Since there is no universal accelerometer, each one is intended to encompass the characteristics of a concrete application best, the way of stressing the photosensitive medium in the first place, the design,, as well as the other characteristics, vary from one construction to another.