Award

The U.S. Navys VLF/LF Submarine Broadcast remains vital to Americas strategic defense, providing reliable means to command submarines at depth, as well as other fleet assets, using high power radio stations all over the globe. The five major VLF stations with their enormous high-Q antennas presently experience radiated-power limitations and poor DC-to-VLF conversion efficiency when sending the customary 200 baud MSK with its 100 Hz frequency shifts. Dynamic tuning of the antennas series inductance removes antenna bandwidth as a performance limitation by creating a constant, purely resistive transmitter load on both the MARK and SPACE frequencies. As demonstrated in Phase 1 of this work, an IGBT switched inductor accomplishes this. However, switching the high levels of current and voltage at an operational VLF transmitting station presents a formidable task.