Access Point (AP) Antenna Replacements

August 21, 2013 at 10:00 AM

 

Upgrading the antennas on your WiFi access point: How to determine the correct AP connector

 

Our technical support department often answers questions like: "How do I upgrade my access points' antennas?" or "How do I identify the type of connector on my WiFi access point or router?" There are a few simple steps to adding or replacing the antenna on your wireless product.

 

First you must check to see if the antennas on your access point are removable.

 

                               Front of an EnGenius wireless access point (AP) showing antennas behindBack of an EnGenius wireless access point (AP) showing antennas

Front and back of a WiFi Access Point showing removable rubber duck antennas installed

 

Back of an EnGenius wireless access point (AP) showing antennas removed

Back of a WiFi Access Point showing rubber duck antennas removed.

 

Next you should identify the type of connector the antenna jack is on the access point. One tip is to check with the manufacturer's website or user manual for your specific make and model listing for the antenna connector type. If you cannot find it on the manufacturer's web site, you can compare it with our common RF connector chart shown below.

 

Common RF Coaxial Connectors

 

Also, you may want to upgrade to a higher gain rubber duck antenna on your access point to increase the signal range and strength. View our 2.4 GHz Rubber Duck antenna selection.

 

Or you might want to connect your access point to an outside antenna. In this case you will need to connect a low loss coax pigtail cable to your access point and then to a longer antenna feeder cable to reach the outside antenna as illustrated below.

 

Illustration of low loss coax pigtail used to connect wireless AP to an antenna

Quick tip: If you need a new antenna, try L-com's Antenna Product Wizard to make your search easier. The wizard will walk you through three steps to identify antennas that match your criteria.

What Does MIMO Mean?

August 7, 2013 at 10:00 AM

Multiple-in/Multiple-out Antennas (MIMO) Explained

 

MIMO Panel Antenna Showing Multiple Coaxial Lines

Most antennas have worked very simply: a frequency transmitted from one antenna could be picked up by a antenna tuned to receive it a distance away without the need of cables between them. While this basic description of a wireless system works, today we have many ways to improve upon the basic concept to increase things like redundancy and coverage. One of those methods is MIMO, which stands for multiple-in multiple-out.

 

MIMO antennas are actually several antennas all within a single physical item or radome. They co-exist either by working in different bands (as the IEEE standard 802.11n works, in both 2.4 GHz and 5.8 GHz) or different polarities, or both. By breaking the data into separate signals and broadcasting them over multiple antennas, MIMO systems can pick from the strongest signal no matter what the environmental conditions.

 

If you have a radio, access point, router or other wireless device that uses MIMO transmission, you will usually see separate jacks for the different signals. Likewise, a MIMO antenna will have multiple jacks or cables to hook up. Once they are plugged in, the antenna takes advantage of a phenomenon called "multipath", which refers to the way multiple signals bounce off of objects and arrive at the receiver at slightly different times.

 

Quick note: L-com's HyperLink® MIMO antenna product center includes options for many popular bands and antenna types.

Low Loss Coaxial Cable for Wireless Applications

June 26, 2013 at 10:00 AM

 

Closeup of Low Loss Coaxial Cable Stripped to Show Components

Even in a wireless network, cables and wires are still used to connect components together (access points to amplifiers, amplifiers to antennas, etc). Each component needs cabling to interact.

 

If you are a wireless engineer and need to interconnect components, chances are you are using low loss coaxial cabling. While 50 Ohm RG-style coax is sometimes used, the attenuation is usually too much for any length over just a few feet. This is where low loss coaxial cable comes in.

 

 

Coaxial Cable and RG-Style Coax

 

All coaxial cable works the same way: the signal is run over two "axes" (thus the name). Coaxial technology is one of the oldest signal cabling types, and is still used today for a specific reason: it is robust and can carry a signal very well over a long distance. In general, the thicker the cable, the less "loss" or attenuation of signal there is over the length of the cable.

 

The original standards for coaxial cable were set forth by the US military. These cables used the term "RG" (for "Radio Guide" or "Radio Government") followed by a number to designate the standard. This worked well at the time, but as technology became more and more utilized in commercial and non-military applications, the restrictions of the standard became less rigid (to the point where RG316, for instance, may have very different properties today depending on who manufactures it).

 

 

Times Microwave LMR® Cables

 

No matter who makes the RG-style cables, they have one fundamental problem: the signal degrades over the length of the cable until it is no longer useable. For shorter use in labs or machine-to-machine applications, this is not a problem. But in wireless applications, the signal integrity up until it is broadcast through the antenna is critical.

 

For that reason, Times Microwave Systems developed a low loss version of coax that it branded as its LMR® series coax. The newly-engineered solution offered far lower loss and better RF shielding, making them a much better choice for wireless systems than the RG styles.

 

Outside of Times Microwave Systems' product (the term LMR® refers specifically to Times Microwave Systems product and is trademarked for their use), several other companies now offer low-loss coaxial cables. These generally follow a similar naming convention as what Times Microwave Systems uses: a three-digit "series" number that refers to both the thickness of the cable and the low loss properties.

 

For instance, 100-series low loss coax is thinner and has greater loss than 200-series, which is thinner and has greater loss than 400-series, etc.

Diagram of most common low-loss coaxial cables

Note that with thicker cable factors such as cable weight and flexibility must be considered. However, there are now ultra-flex versions of thicker series like the 400-series that offer similar loss characteristics but are far more flexible.

 

Quick note: L-com has been manufacturing high-quality coaxial cables and components for over thirty years.
 

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.
 
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