The U.S. Navy seeks solutions for an Expeditionary Very Low Frequency (ExVLF) transmitter system, a modular, relocatable communications suite for 24/7 data broadcasts to maritime and shore-based nodes. The system must be housed in a 20-foot ISO container, hardened for rugged environments, and integrate with Government-Furnished Equipment, including an aerostat-lofted tethered antenna. Initial efforts will focus on a prototype delivery phase, with potential options for follow-on production units. The government is interested in mature commercial technologies and prototype efforts, with a preference for solutions deployable to meet DoD security standards. Performance location is not specified, and no budget amount is provided.