Directional Antenna vs. Omni Antenna

April 4, 2016

Some people just look at the gain of an antenna to determine what to buy.  They want the biggest and baddest gain thinking that is the best measurement of an antenna.  Gain, the ability to collect or broadcast signal is important, but it may not be the most important factor.  On factor that most inexperienced people overlook about exterior (donor) cellular antennas is their radiation pattern, or the way they collect and broadcast signal.
 

Directional Antennas

Directional antennas usually have the strongest gain.  Think if these antennas like a flashlight, with a beam focused in a single direction.  Like a flashlight, a directional antenna doesn't see much except what is in the direction it is pointing.  Directional LPDA antennas may have about a 45 degree horizontal beam, but for more focused directional Yagi antennas may have a much narrower beam in the range of 20 or 30 degrees.  Below is an image of a directional LPDA antenna.
 
Directional Antenna
Directional antennas work best under the following conditions:
 
  • All the signal is coming from the same direction.
  • There is good line of site from the antenna to the cell tower.
  • There is no heavy forest blocking signal.
  • There is no mountainous terrain between the antenna and cell tower. 
Trees, mountains and canyons may cause cell signal to bounce, altering the direction of the signal.  This makes it difficult to tune a directional antenna toward the signal.  Directional antennas are also used to reduce signal by pointing the antenna away from a tower.  This is done when the cell signal is too strong and overloading cell signal booster equipment.
 

Omni Antennas

Omni antennas usually don't have as strong a gain as directional antennas.  Omni antennas are like light bulbs, they broadcast and collect signal from all directions similar to the way light bulbs shine their light in all directions.  Omni antennas have a 360 degree beam, allowing them to work with signal from multiple towers in multiple directions.  Below is an image of an Omni antenna.
 
Omni Antenna
 
Omni antennas work well under the following conditions:
  • Signal is coming from multiple carrier tower in different directions
  • Urban situations with tall buildings bouncing signal in different directions
  • Mountainous or canyon situations where signal bounces in different directions.
Overall, Omni antennas are a good all-around antenna to use in most situations.  The gain of an omni is less than a directional, but the capabilities to collect signal from all directions
makes it an excellent choice for multi-carrier, multi-frequency cell signal booster systems.