The stealth coating on the U.S.-made fifth-generation fighters shields the aircraft from high-frequency radars operating in the Ku, X and C bands and some of the S band, but not from low-frequency systems utilizing L, UHF and VHF wavelengths, according to an article by Dave Majumdar at USNI News.
China and Russia are now working to develop low-frequency radars with more computing power designed to track stealth aircraft with more precision -- enough to target them with a missile, according to the report, citing an unnamed former senior U.S. Navy official.
"Acquisition and fire control radars are starting to creep down the frequency spectrum," the official told USNI News. "I don't see how you long survive in the world of 2020 or 2030 when dealing with these systems if you don't have the lower frequency coverage."
To be sure, the Defense Department is aware of the increasing sophistication of enemy air defenses, known in military parlance as anti-access, area-denial, or A2-AD, environments.
The Pentagon's latest annual report to Congress on military and security developments in China notes the country is continuing its military build-up and views defense against stealth aircraft and drones as "a growing priority."
The People's Liberation Army, or PLA, has long sought to control the flow of information in the event of war to thwart data-hungry adversaries such as the U.S. It considers the strategy of "information dominance" a critical form of defense against countries that it views as "information dependent," according to previous assessments.
Perhaps not surprisingly, the People's Liberation Army Navy, or PLAN, sent an uninvited spy ship, probably the type 815 Dongdiao-class intelligence collection vessel Beijixing (pennant number 851), to this year's Rim of the Pacific exercise, according to an article by Sam LaGrone of USNI News.
China is participating in the event -- the world's largest naval exercise, held off the coast of Hawaii -- for the first time this year, with four vessels.
The head of U.S. Pacific Command, Adm. Samuel Locklear, this week described the presence of the surveillance ship as "a little odd," though it "hasn't created any difficulties in the exercise," which ends Friday.