In the traditional field of wireless communication, the application of long-wave communication is constrained on small and medium-sized platforms due to the requirement of large sized signal-transmitting antennas. This paper proposes and develops a three-degree-of-freedom cut-out beam structure of the vibration permanent magnet type mechanical antenna prototype based on the inverse piezoelectric effect, vibration theory, and Maxwell’s equations. It establishes an electric-mechanical-electromagnetic energy theory model and investigates the radiation influencing factors of the mechanical antenna along with its frequency modulation technique. The experimental results validate that electromagnetic wave signals can be frequency-modulated by exciting different vibration modes of the mechanical antenna prototype. This research offers novel theoretical and technical perspectives for low-band signal communication.