A ship's MF-HF whip antenna breaks off and is carried away in a storm. What would you do to regain operation on MF-HF GMDSS frequencies?
β’ MF-HF GMDSS antennas are usually long wire or whip antennas matched by an antenna tuner/ATU located close to the feed point β’ Correct antenna length is related to the wavelength (Ξ») of the frequencies used, often some fraction like quarter-wave for efficient radiation β’ MF-HF GMDSS equipment manuals specify minimum and recommended antenna lengths for safe and effective operation
β’ What is the approximate wavelength of MF frequencies (around 2β3 MHz) and HF frequencies (say 8β12 MHz), and would a 10 ft antenna be a reasonable fraction of that wavelength? β’ Why is it important that the MF-HF antenna be a long vertical or long-wire radiator, and how does that compare to a short dipole or a VHF antenna? β’ Which option most closely matches what a typical MF-HF GMDSS installation manual would recommend for an emergency/temporary wire antenna when the whip is lost?
β’ Compare each proposed antenna length against a realistic fraction of the wavelength for MF-HF (is 10 ft long or 35β40 ft closer to whatβs normally used?). β’ Check whether connecting MF/HF gear to a VHF antenna makes technical sense, given VHF operates near 156 MHz (very short wavelength) vs. MF-HF (much longer wavelength). β’ Confirm which option mentions following the equipment instruction manual, which is a key principle in GMDSS equipment setup and repair.
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