FMF - Fleet Marine Force Combat Communications Questions and Answers 1 — Questions and Answers
Question 1: A Marine operating a frequency-hopping, encrypted radio net can hear the net control station, but their own transmissions are received as garbled audio. Power, antenna, and frequency settings are confirmed correct. What is the MOST likely cause of this communication failure?
- The squelch setting on the radio is incorrect.
- The operator is too far from the retransmission site.
- The wrong COMSEC key is loaded, or the Time of Day (TOD) is incorrect. (Correct answer)
- The radio's battery is too low to transmit clearly.
Correct answer: The wrong COMSEC key is loaded, or the Time of Day (TOD) is incorrect.
In a frequency-hopping, encrypted net, all radios must have the correct Communications Security (COMSEC) key and be synchronized with the correct Time of Day (TOD). A mismatch will cause the encryption and hopping pattern to be out of sync, resulting in garbled or no communication, even if the base frequency is correct.
Question 2: Which of the following BEST describes the primary function of the Single Channel Ground and Airborne Radio System (SINCGARS) in Frequency Hopping (FH) mode?
- To provide long-range, over-the-horizon communication by bouncing signals off the ionosphere.
- To increase the transmission power for communicating through dense urban terrain.
- To rapidly change frequencies during transmission to prevent enemy jamming and interception. (Correct answer)
- To operate on a single, powerful frequency to ensure all subordinate units hear the transmission.
Correct answer: To rapidly change frequencies during transmission to prevent enemy jamming and interception.
The primary feature of SINCGARS in Frequency Hopping (FH) mode is its ability to change frequencies over 100 times per second across a specified range. This makes it extremely difficult for an enemy to intercept the transmission or effectively jam the communications.
Question 3: A patrol makes initial contact with a significant enemy force, and the report must be sent immediately, taking precedence over all other radio traffic. Which message precedence proword should be used?
- IMMEDIATE
- FLASH (Correct answer)
- PRIORITY
- ROUTINE
Correct answer: FLASH
The order of message precedence from highest to lowest is FLASH (Z), IMMEDIATE (O), PRIORITY (P), and ROUTINE (R). FLASH is reserved for initial enemy contact reports or operational messages of extreme urgency.
Question 4: The AN/PRC-117G is known as a "multiband" radio, giving it great versatility. This is due to its ability to operate across which of the following frequency bands?
- High Frequency (HF) and Very High Frequency (VHF)
- Ultra High Frequency (UHF) and Super High Frequency (SHF)
- High Frequency (HF) only
- Very High Frequency (VHF) and Ultra High Frequency (UHF), including SATCOM. (Correct answer)
Correct answer: Very High Frequency (VHF) and Ultra High Frequency (UHF), including SATCOM.
The AN/PRC-117G operates in a wide frequency range from 30 MHz to 2 GHz. This covers the VHF band (for line-of-sight communications like SINCGARS) and the UHF band (for line-of-sight and satellite communications), making it a highly versatile multiband radio.
Question 5: You are attempting to establish communication but cannot hear the distant station. You have already checked your radio's power, volume, frequency, and antenna connection. According to standard troubleshooting procedures, what is a logical next step?
- Attempt to contact the station using a different radio. (Correct answer)
- Immediately disassemble the radio to check for internal faults.
- Assume the distant station's radio is broken and cease attempts.
- Replace the battery, even if it shows a partial charge.
Correct answer: Attempt to contact the station using a different radio.
A key step in troubleshooting is isolating the problem. By trying a different radio (if available), you can quickly determine if the fault lies with your specific piece of equipment or with another factor, such as range, terrain, or an issue with the distant station. This is a more logical and efficient step than assuming the fault or performing maintenance beyond the operator's level.
Question 6: What is the primary purpose of Communications Security (COMSEC)?
- To ensure radio transmissions are loud and clear.
- To deny unauthorized persons information derived from telecommunications and ensure the authenticity of such communications. (Correct answer)
- To catalog and track all communication equipment within a unit.
- To assign radio frequencies to prevent friendly units from talking over each other.
Correct answer: To deny unauthorized persons information derived from telecommunications and ensure the authenticity of such communications.
COMSEC encompasses all measures taken to protect telecommunications from unauthorized interception and exploitation while also ensuring that the communications are authentic. This includes using encryption, controlling cryptographic keys, and implementing secure procedures.
FMF - Fleet Marine Force Combat Communications Questions and Answers 1
A Marine operating a frequency-hopping, encrypted radio net can hear the net control station, but their own transmissions are received as garbled audio.
Power, antenna, and frequency settings are confirmed correct.
What is the MOST likely cause of this communication failure?
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