Subelement B: MF-HF-DSC-SITOR (NBDP) Equip. & Operations— Topic :
Question 22B4
Element 9 (GMDSS Maintainer)Which of the following coaxial cables is suitable for use in GMDSS MF/HF antenna systems?
Explanation
Most amateur radio and commercial radio communications systems, including GMDSS MF/HF equipment, are designed for a characteristic impedance of 50 ohms. This standard impedance minimizes signal reflections and maximizes power transfer between the radio, transmission line, and antenna.
RG-8 is a common type of 50-ohm coaxial cable suitable for these applications, particularly for the higher power and lower frequencies associated with MF/HF maritime radio. Using a cable with a different impedance, such as the 72/75-ohm options (RG-59, RG-6, RG-179), would create an impedance mismatch. This mismatch leads to a high Standing Wave Ratio (SWR), causing significant power loss, increased cable heating, and potential damage to the radio's final amplifier stage.
Related Questions
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