🔍 Key Concepts

• HF propagation and ionosphere: How higher vs lower HF frequencies behave in daylight vs darkness over long distances. • Great-circle distance: San Francisco to Taiwan/Philippines is an intercontinental, ocean-spanning path, not a short coastal hop. • Typical maritime HF bands: Common long-range working bands (4, 6, 8, 12, 16, 22 MHz) and which are favored for very long paths in day vs night.

💭 Think About

• For a multi-thousand‑mile ocean path, do you generally need lower or higher HF bands compared with a few‑hundred‑mile coastal path? • In general HF practice, are higher frequencies more usable in daylight or in darkness, and when do you shift down to lower frequencies? • Look at each option and ask: Which one pairs relatively higher HF bands with daylight and relatively lower HF bands with darkness for a very long path?

✅ Before You Answer

• Eliminate any option that uses very low HF/MF bands (around 2 MHz) for trans‑Pacific distances; those are mainly for regional/night coastal work. • Check whether the option’s day vs night frequency order makes physical sense: higher by day, lower by night, not the other way around. • For an intercontinental route, verify that the daytime choice includes one of the upper HF maritime bands (16 or 22 MHz) rather than only mid‑HF like 6 or 8 MHz.