text: Communications
  Figure 6-11. Bidirectional antenna pattern.
  Application
  6-96. Bidirectional antennas are usually used on point-to-point circuits and in situations where the
  antenna null can be positioned to reduce or block signals that could interfere with reception.
  Orientation
  6-97. To work properly (radiate in the desired directions), a bidirectional antenna must be oriented to
  the ground wave, and this is difficult to do. Lowering the antenna to create a near-vertical-incidence
  skywave (NVIS) effect makes this more difficult, because it increases the radiation pattern. A bidirectional
  antenna is best used near other antennas, which should be placed in its null to reduce interference and
  interaction between the antennas.
  Examples
  6-98. The bidirectional antennas most commonly used in tactical situations are the sloping-"V,"
  random-length wire, and half-wave dipole.
  OMNI-DIRECTIONAL ANTENNA
  6-99. An omnidirectional antenna (Figure 6-12) radiates and receives energy equally well in all compass
  directions. It is used when it is necessary to communicate in separate directions at once. However, it is also
  more susceptible to interference from all directions. The most common omnidirectional antenna is the
  whip. Some others are the quarter-wave vertical (RC-292 and OE-254) and the crossed dipole
  (AS-2259) antennas.