114. Communications

Question 1

Define HF and discuss its basic applications

Answer 1

3 – 30 MHz.

• Capable of both long and short-range secure voice and data comm.
• Capable of traveling around the world in the right conditions; has over the horizon capabilities
• HF transmission may be intercepted/traced by enemy hundreds of miles away.
• Two types of HF Propagation: Ground Wave & Sky Wave

Question 2

What are the modes of HF radio wave propagation?

Answer 2

• Ground wave: Transmission of a signal along ground surface. Range decreased by heavy vegetation (Camp Lejeune), mountainous terrain (Camp Pendleton), or dry desert soil (29 Palms).
• Sky wave: Involves signal bending by the ionosphere.At least two frequencies are required during 24-hour period: a low, night frequency and a higher, day frequency.

Question 3

Define VHF and discuss its basic applications

Answer 3

30 – 300 MHz.

• Primary MAGTF radio single-channel ground & airborne radio system (SINCGARS).
• Primary means of communications for C2 and fire support on battlefield
• Provides high security against threat electronic warfare (EW) by using frequency hopping with integrated COMSEC.
• Primary limiting factors are range (up to 10 miles) and frequency availability.

Question 4

What is SINCGARS?

Answer 4

Single Channel Ground and Airborne Radio (SINCGAR) set, AN/PRC 119. It can be used as a man pack radio or a vehicle mounted radio. Uses VHF.

Question 5

What are the two modes of operation for the SINCGARS?

Answer 5

Single Channel – When in SC mode, you are operating on one frequency.
Frequency Hopping – FH mode is used for secure transmissions due to the radio frequency constantly shifting to reduce or eliminate the threat of jamming, interception, and direction finding

Question 6

What are the three levels of security classification?

Answer 6

Top Secret: unauthorized disclosure could reasonably be expected to cause exceptionally grave damage to the national security

Secret: unauthorized disclosure expected to cause serious damage to the national security

Confidential: e unauthorized disclosure expected to cause damage to the national security

Question 7

Define UHF and discuss its basic applications

Answer 7

300 MHz - 3GHz

• Used primarily in forward air control (ground to air)
• Has good counter-counter electronic measures
• Limiting factor is range; Line of sight crucial