Extra exam question E3A06
Subelement E3, RADIO WAVE PROPAGATION· Group E3A
What should be done to continue a long-distance contact when the MUF for that path decreases due to darkness?
- A.Switch to a higher frequency HF band
- B.Switch to a lower frequency HF band (correct answer)
- C.Change to an antenna with a higher takeoff angle
- D.Change to an antenna with greater beam width
WhyAs the maximum usable frequency for an HF path drops with approaching darkness, keeping a contact going usually means switching to a lower frequency HF band. As darkness falls along an HF path, the ionosphere's ionization drops and the maximum usable frequency for that path falls with it, so keeping a contact going as the MUF decreases usually means moving to a lower HF band that's still below the new, lower MUF, answer B. Switching to a higher band would put the signal above the now-lower MUF where it just passes through the ionosphere instead of refracting back down, and changing antenna takeoff angle or beamwidth doesn't address a band's MUF dropping.
Published 2026-08-28 · Last updated 2026-08-28 · Question text is verbatim from the 2024-2028 NCVEC Element 4 pool (public domain); the explanation above is original writing, see our methodology.
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