text: Chapter 6
  Figure 6-10. Unidirectional antenna pattern.
  Application
  6-91. Directional antennas are used on long-range, point-to-point circuits that need concentrated radio
  energy to ensure a reliable signal.
  Orientation
  6-92. A directional antenna concentrates most of its energy in one direction, so it requires careful
  orientation.
  Detection
  6-93. The enemy has a hard time determining the origin of directional antennas, which minimizes
  interference.
  Adaptation of Bidirectional Antennas for Directional Use
  6-94. Adding a terminating resistor to absorb the energy of the second lobe allows directional use of a
  bidirectional (long-wire or sloping "V") antenna. The terminating resistor must match the antenna. That is,
  it must be able to absorb one-half of the power output of the connected transmitter and provide 400 to
  600 ohms of resistance.
  BIDIRECTIONAL
  6-95. A bidirectional antenna (Figure 6-11) has two opposite lobes of radio energy, with an area of null
  energy (no energy) between them. The lobes produce two strong signals in opposite directions, and weaker
  ones in all other directions.