Wireless LOS Terminology

November 28, 2013 at 10:00 AM

Why Line of Sight (LOS) is so important

 

Sample of LOS and Fresnel Zone Diagram

When designing an outdoor wireless network, ask yourself this: what is between point A (antenna 1) and point B (antenna 2)? This path between two antennas is referred to as the Line of Sight (LOS).

 

There are three main categories of Line of Sight. Full Line of Sight (LOS) is where no obstacles reside between the two antennas. Near Line of Sight (nLOS) includes partial obstructions such as tree tops between the two antennas. Lastly, Non Line of Sight (NLOS) is where full obstructions exist between the two antennas.

 

By determining the specific Line of Sight conditions in the WiFi network area you can then determine the correct type of wireless system to install.

 

Another common term to be aware of is The Fresnel Zone, referenced in the diagram above. It is is an electromagnetic phenomenon where light waves or radio signals get diffracted or bent from solid objects near their path. The radio waves reflecting off the objects may arrive out of phase with the signals that traveled directly to the receiving antenna, thus reducing the power of the received signal.

 

Line of Site (LOS) Overview Diagram

Print and post the above diagram.

 

For indoor wireless network installations it is important to consider obstacles such as walls, ceilings, and furniture that will affect Line of Sight since these all play a role in wireless signal reception. In wireless transmissions, reflections (when wireless signals "bounce" off objects) and multipath (when wireless signals travel in multiple paths arriving at the receiver at different times) are as important as signal strength in determining the success of an installation. A signal will also exhibit peaks and nulls in its amplitude and alteration of its polarization (vertical or horizontal) when propagating through walls, ceilings and reflecting off metallic objects. 

 

Path Loss is another area of concern when dealing with Line of Sight. For instance, although 2.4 GHz signals pass rather well through walls, passing through trees and leaves is a challenge. This is due to the difference of water content in each. Radio waves in the 2.4 GHz band absorb into water very easily, so the high level of moisture in trees or leaves would trap the waves. When faced with nLOS or NLOS conditions due to trees, 900 MHz is your best choice as it is not absorbed like 2.4 GHz.

 

 

Click here to shop L-com’s Hyperlink brand wireless products.

  

How to Install Grid Antennas

July 24, 2013 at 10:00 AM


Grid Antenna Mounted on a Mast or Pole with Downward Angle

To make installation for your application easier, here’s a rundown of what to look for. First though, let’s decipher this: why use a Grid Antenna?

 

For point-to-point communications, a grid antenna has a lot of advantages that may make it the best choice for your application. First- since they are directional, they can provide better gain by focusing the beam in a particular direction. Second, though they are typically larger than other antenna types, they usually break down easily to fit in a box for easy transport to the installation site, or for storage while not being used.

 

Once assembled, the grid provides better wind loading than dish antennas. They are very also very easy to mount in either vertical or horizontal polarization and easy to tilt for precise aiming.

 

 

Assembly

 

We suggest double-checking the quality of the antenna before you purchase, especially if the installation is outdoors. The grid should have a UV protective coating and all of the hardware should be stainless steel.

 

When you order a grid antenna, it usually comes disassembled. Different manufacturers make grid antennas with slightly different installation instructions. When putting the grid antenna together, take all normal safety precautions to avoid coming into contact with dangerous electrical lines, etc., then go over the parts list. All grid antennas need the grid itself (often broken into two halves to reduce shipping costs), mounting "L" bracket, mast clamps, hardware such as screws, nuts and washers, and the feed horn. The feed horn is the long, protruding piece in the center of the grid that sends the actual signal. The below video (or this tutorial) demonstrates step by step assembly of the grid antenna. 

 

 

Where can you find a reliable antenna? L-com's HyperLink® line of grid antennas features tons of options for 2.4 GHz and 5.8 GHz bands, along with specialty versions for the 900 MHz, 1.9 GHz, 3.5 GHz and 4.9 GHz. Many options are available in convenient 5-packs that save you time and money. There are also hardware packages for replacing or maintaining components of a grid antenna.
 

Picking the Right Antenna for Your Application

May 29, 2013 at 10:00 AM

 

How-To 

 

A log periodic antenna mounted on a pole or mast

If you are new to wireless technology, the multitude of antenna shapes, sizes, styles and gains can be bewildering at first. Will you need a dish antenna, a grid, a Yagi or just a rubber duck?

 

Fortunately, by following a few rules of thumb, you can get a hang of the different styles and the applications they fill. It starts with a complete survey of the area where you need coverage: its shape, size and obstructions found within it. With these details on hand, you'll need to consider the following factors:


 

Beam Width


One of the key differences between antenna styles is the "beam width" and direction. In general, the narrower the beam width the more powerful the signal is in a particular direction. That's not to say Omni directional antennas are weak, but merely that the signal strength is spread in a different way (which may or may not be appropriate for your application).

 

Read this article for more information on signal gain patterns and wireless network design.

 

Vertical and horizontal beam patterns
Beam Pattern of a Log Periodic Antenna

 

 

Antenna Polarity

 

Another aspect of antennas to keep in mind is the polarity. While wireless signals travel, they move as a wave. Just like ripples on the surface of water, waves that move in the same direction cancel each other out. Waves in different directions do not. In a similar way, too many antennas set up in a vertical polarization in an area can cancel each other out, resulting in extremely poor signals.

 

In the case where a lot of wireless signals in the same band may be required, setting up antennas with different polarities can improve the performance of each signal. In some instances, you may want to set up "dual polarized" antennas, which include both vertical and horizontal polarities. These and other types of polarities (such as "cross polarized" and "circular polarized") can improve the strength and distance of signals in multiple ways.

 

This article offers some great information on antenna polarization.

 

Antenna Polarization Diagrams
WiFi Antenna Polarization Schemes

 

 

Antenna Gain

 

The final consideration for choosing your antenna is antenna gain. Measured in decibels (dB), it is commonly written as a number followed by "dBi" (the "i" at the end is for "Isotropic", and indicates that the number is relative to an imaginary, "perfect" dipole radiation). In general, the higher the dBi the stronger the signal in whatever direction it is going.

 

While it may seem tempting to simply buy the antenna with the highest gain for your beam width and polarization, it may not be relevant for your application. You should seek a dBi relative to the size of the space that the signal needs to cover. In many cases, a high gain will provide poor coverage closer to the antenna and better coverage further away.

 

For instance, setting up an Omni directional antenna in the center of a small cafe would require a smaller gain. If you use an antenna with too large a gain, people using devices in the street outside of the cafe would have better signal than those in the cafe itself because the total signal would be stretched.

 

This article explains why too much gain is a bad thing.

 

Small gain antenna used in 300-foot courtyardLarge gain antenna used in 1000-foot courtyard
An 8 dBi Omni directional antenna is more appropriate for a 300' space in a cafe courtyard than a 14 dBi antenna.
 

Quick note: L-com's technical resources section has tons of helpful information for the WiFi newbie or established expert alike. Also, for help selecting an antenna, try the Antenna Product Wizard.

 

What is an Omni directional antenna for 2.4 GHz?

May 15, 2013 at 10:00 AM

 

Omnidirectional antenna

As wireless technology continues to grow and develop, several antenna shapes and designs have arisen to provide different types of coverage. An Omni directional antenna is so called because it provides a wireless signal in a 360° radius, or in "all directions". These types of antennas are very common, and typically look like a very straight, stick-like shape.

 

Since the energy of the signal is not directional or pointed in a specific way, Omni directional antennas tend to be of lower gain than directional antennas such as parabolic dish, Yagi, and panel style antennas. However, higher gain isn't usually required for small installations such as Wi-Fi "hotspots" in stores and cafes. For those kinds of applications, a single Omni directional antenna installed near the center of the location often does the trick.

 

The 2.4 GHz band is typically designated for Wi-Fi use, and is the most common band for things like laptop and tablet wireless access. Therefore, if you are setting up a network for customers or visitors to access the Internet wirelessly, you'll often be installing a 2.4 GHz antenna. However, check the specifications of the access point that is being hooked up to the antenna to make sure the frequencies match. 

 

Quick note: L-com has a huge selection of 2.4 GHz antennas, from parabolic dish antennas, to Omni directional and everything in between.
 

Identifying Array Antennas

April 17, 2013 at 10:00 AM

What are they?


An antenna array is a group of two or more directional (usually panel style) antennas that are grouped together to form an Omni directional signal. Many times an RF splitter is used to connect the multiple antennas to a single access point or WiFi amplifier.

 

The benefit of using an antenna array over a single Omni directional antenna is that the antenna array provides radiation patterns that a single Omni antenna would not. Many times antenna arrays provide greater coverage than a single Omni antenna could.

 

 

Antenna array mounted on a pole RF splitter connected to an antenna array
Antenna array mounted on a pole RF splitter connected to an antenna array

Down tilt mounting feature
Down tilt mounting feature 

 



Where Would You Use Them?


Antenna arrays are used in outdoor point-to-multipoint applications. L-com's antenna arrays are available in 90° (4 panels), 120° ( 3 panels), and 180° (2 panels) configurations and include appropriate splitter and cables. Additionally, these antenna arrays feature zero to 20° down tilt capability to compensate for the geography of the installation location. This helps ensure maximum wireless signal coverage in the service area.

 

 

Antenna Array Configurations Available

 

 

Antenna Arrays with four 90° sectorial antennas Antenna Arrays with four 90° sectorial antennas
Antenna Arrays with three 120° sectorial antennas Antenna Arrays with three 120° sectorial antennas
Antenna Arrays with two 180° sectorial antennas Antenna Arrays with two 180° sectorial antennas
 

All sectorized omni array configurations are designed to all-weather operation. They feature both heavy-duty polymer antenna radomes and stainless steel mounting systems. 

 
  
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