Subelement A: VHF-DSC Equipment & Operation— Topic :
Question 6A5
Element 9 (GMDSS Maintainer)What is the most common type of emission for shipboard VHF-DSC transceivers?
Explanation
Shipboard VHF-DSC transceivers are primarily used for two main functions: voice communication and Digital Selective Calling (DSC). While DSC uses a digital emission type (such as F1B or G1B for data), the most common, day-to-day emission type utilized by these transceivers is for analog voice communication.
The emission designator G3E describes this:
* **G:** Indicates Phase Modulation, which is a form of Frequency Modulation (FM). Marine VHF radios use FM for voice.
* **3:** Denotes a single channel carrying analog information.
* **E:** Specifies Telephony, meaning voice communication.
Therefore, G3E represents the standard narrowband FM voice operation common on marine VHF radios. Options B (J3B) and D (H3E) signify Single Sideband (SSB) telephony, which is not used for voice on marine VHF. Option A (F1B) describes Frequency Shift Keying (FSK) digital telegraphy, which is used for DSC but is less common in overall transceiver usage than voice.
Related Questions
6A3 How is pre-emphasis used in an FM transceiver?6A4 A modulation index set to less than 1 to 1 may result in what?6A6 How many sidebands does a VHF FM transmitter have?7A1 What condition may be indicated if a VHF radio is unable to contact nearby stations and an inline wattmeter indicates power outputs of 1 watt (LOW power) mode and 8.5 watts (HIGH power) mode with +12.8 vdc applied to the radio’s DC line?7A2 Antenna system matching can be analyzed by determining the Standing Wave Ratio (SWR). Which of the following is the best test procedure to measure the SWR of a marine VHF antenna system?