Which statement about HF is true?

Which statement about HF is true?

• A. Space-to-space communications
• B. Ground-to-ground but not for submarines
• C. Submarine communications
• D. Has no naval uses

Answer: (C)

High-frequency radio waves travel long distances by reflecting off the ionosphere, giving beyond-line-of-sight reach. This makes HF ideal for long-range naval communications, including links to ships, aircraft, and shore stations. Submarines can also receive and transmit HF when they are near the surface or using an antenna extended above the water, so HF serves submarine communications in those conditions. The other statements mischaracterize how HF propagates or how submarines use radio: space-to-space typically relies on higher bands and satellites; ground-to-ground can use HF but the claim about submarines is inaccurate; and there are clear naval uses for HF.

High-frequency radio waves travel long distances by reflecting off the ionosphere, giving beyond-line-of-sight reach. This makes HF ideal for long-range naval communications, including links to ships, aircraft, and shore stations. Submarines can also receive and transmit HF when they are near the surface or using an antenna extended above the water, so HF serves submarine communications in those conditions. The other statements mischaracterize how HF propagates or how submarines use radio: space-to-space typically relies on higher bands and satellites; ground-to-ground can use HF but the claim about submarines is inaccurate; and there are clear naval uses for HF.