Annex B09 HF Antenna Selection/Field Expedient Antennas

Question 0

Near Vertical Incidence Sky Wave (NVISW)

Answer 0

Technique for transmitting over relatively short ranges by ionospheric refraction using very high incident angles

NVIS is simply sky wave propagation that uses antennas with high angle radiation and low operating frequencies

Question 1

Five (5) planning factors when selecting an antenna

Answer 1

Propagation
Distance
Coverage
Construction Materials
Site

Question 2

Two (2) antennas that meet requirements for NVIS propogation

Answer 2

AS-2259

Half Wave Dipole

Question 3

Five (5) components of field expedient antennas and their purpose

Answer 3

Insulators: keeps the antenna from being shorted to ground and being rendered ineffective
Masts: Physically support the antenna
Guys: Ropes/Wires that stabilize the masts
Resistors: Used to make certain antennas directional
Elements: The antenna itself, radiates the wave

Question 4

Match the components of an antenna to their location

Answer 4

.

Question 5

Given a frequency, calculate the physical length in feet of a half wave dipole antenna

Answer 5

Total dipole length in feet is 468/freq

Ex:
Freq=11.7MHz
4688/11.7=40ft
40/2=20ft per element

For slash wire, divide 451 instead of 468