The radio antenna project has come under scrutiny because the wave types emitted by the Wireless Electromagnetic Method (WEM) project, namely extremely low frequency (ELF) radio waves, are considered "possibly carcinogenic to humans" by the International Agency for Research on Cancer.
China's first ELF-emitting facility, a 1,400-mile project, was finally completed after 13 years, the South China Morning Post reports. The radio antenna facility's location hasn't been disclosed, though SCMP says it is somewhere in the central Huazhong region.
ELF waves have frequencies ranging from 30 to 3 Hz, meaning their wavelengths can be up to 10,000 and 100,000 kilometers long, respectively. Because of their great lengths, ELF waves are able to communicate small bits of information to submarine crews at depths where seawater would interfere with other radio transmissions.
Russia, the United States and India were previously the only countries believed to have established ELF facilities for communicating with submarines lurking at extraordinary depths. The US Navy's ELF sites operate at 76 Hz, according to a 2001 report by Federation of American Scientists.
ELF broadcast communications allow submarines to retain a "high degree of stealth and flexibility in speed and depth, but are low data rate, submarine-unique and short-to-submarine only," according to GlobalSecurity.org.
"This facility will have important military uses if a war breaks out," said Chen Xiaobin, a researcher at the China Earthquake Administration, according to SCMP.
Regarding the project's secrecy, Chen underscored that "though I am involved in the project, I have no idea where it is," adding that "it should be up and running by now."
Wenming Hu, party secretary of the state-owned China Shipbuilding Industry Corporation, visited the radio site last May, where he "expressed his appreciation for the construction of the WEM project and put forward opinions and requirements for the follow-up development of the project and the technical application in related fields," according to a company statement.
The WEM project will also be used for detecting seismic events and searching for minerals, the Chinese government says.