Subelement G: VHF-DSC Equipment & Comms— Topic :
Question 44G3
Element 7R (GMDSS-RO)Which of the following factors does not normally affect the range of VHF transmissions?
Explanation
VHF (Very High Frequency) transmissions primarily travel via line-of-sight propagation. Signals in this range (30-300 MHz) typically penetrate the Earth's ionosphere rather than being refracted (bounced back to Earth) by it. Therefore, ionospheric refraction does not normally extend the range of VHF transmissions.
In contrast:
A) Salt water ingress into coaxial cable introduces significant signal loss (attenuation) and impedance mismatches, severely reducing the power reaching the antenna and thus limiting range.
B) The power level setting directly affects the strength of the transmitted signal. More power generally leads to a stronger received signal and greater range.
C) Vessel antenna height is crucial for line-of-sight communications. Higher antennas overcome the Earth's curvature more effectively, extending the radio horizon and thus the transmission range.
Related Questions
44G1 Which of the following control selections may result in limited receiving range?44G2 While conducting routine communications using the wheelhouse VHF with a station 1 mile distant, your recommended power setting would be:44G4 Much longer than normal VHF transmissions are typically caused by:44G5 Describing VHF transmissions as "line of sight" does not mean:44G6 The effectiveness of VHF communications is maximized by: