Cat 6 Shielded vs. Unshielded

June 5, 2013 at 10:00 AM


Category 6 cable with drain wire

Category 6 or Cat6 Ethernet cable is designed to provide up to 1 Gbps Ethernet transmission, and is required for 1000 Base-T style networks. However, the choice to use unshielded twisted pairs (UTP) or shielded (or screened) twisted pairs (STP or ScTP) depends on the location of the installation.

 

Typically, the shield is only required in cases where the cable is run through an area of high electro-magnetic interference or radio frequency interference (EMI/RFI), such as output by strong power lines, motors, magnets, and radio antennas. Outside of these situations, the shield does not help provide a faster or clearer signal, and can add more problems than it solves.

 

Pros and cons 

 

Without a shield, Cat 6 UTP cable is already resistant to minor and typical forms of EMI/RFI, such as having a fluorescent light or small motor nearby. In these cases, you should always run the cable at a 90° angle to the source of the interference in order to minimize exposure. Otherwise UTP is cheaper, lighter, and just as effective as STP.

 

If you need STP cable, you have to remember that the shield itself must drain, otherwise EMI/RFI can build up on it and degrade the signal inside. Drainage is typically done at the connection site by using a shielded coupler or jack that is connected to ground.

 

Also note that the weight of shielded cable, while not very heavy, can be significant if you are running multiple cables in an area. In some cases, heavy cabling run above a ceiling or behind a wall has caused collapses and structural damage over time.

 

Quick note: Visit L-com's Ethernet Product Center for a huge selection of common and hard-to-find Ethernet cabling solutions, including shielded, harsh-environment, special jacketed and more.

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.

 

A Tutorial on USB

May 22, 2013 at 10:00 AM

 

What exactly is USB?

USB Cable

 

USB stands for Universal Serial Bus and is a connectivity standard that transfers large amounts of data between devices. While it is far from the first standard designed for this purpose, the need for an effective method to transfer data between devices has become enormous due to the increase in portable and mobile devices.

 

The USB standard does just this, providing a universal method across different products and manufacturers. Other, "proprietary" standards exist, but they are often derivatives of USB with slight changes to the wiring or physical connector type.

 

 

Types of USB Cabling and Connectors

 

In the years since USB was first implemented, there have been three dominant versions, each providing faster data throughput than the last. USB 1.1, sometimes called "full-speed", can transfer data at about 12 Mbps. USB 2.0, which is currently the most common, operates at 480 Mbps. The latest standard, USB 3.0, operates at over 4.8 Gbps (about 10 times that of USB 2.0).

 

The most common USB connector types, Type A and Type B, are the same throughout the different versions. Though, other connector types such as the Mini B4, Mini B5, and Micro B are gaining popularity for their small size, which is preferred in smaller portable electronics such as mobile phones and tablets.

 

However, even if the connectors are similar, the cable itself must be constructed to the standard. For example, a USB 2.0 compliant cable could not pass 4.8 Gbps of data even if it were plugged into a USB 3.0 compliant device.

 

 

Why is USB so popular?

 

USB has several advantages over other standards that are used for the same purpose. First, it is a "hot connection", or has the ability to plug and unplug into a computer without causing it to freeze or causing programs to crash. USB is also uniquely designed to carry some low-voltage power which makes it capable of powering or charging devices that it is plugged into.

 

Also, though most applications only need standard USB cables, another advantage of USB is that it has the capability of specialization. Today we are seeing a rapid expansion of USB applications which require more specialized cabling- outdoor, wet or dusty environments, high-vibration situations, and places where special flame ratings, armor, or angled connectors are required. 

 

Check out our detailed USB tutorial here. Or, if you find yourself in this kind of special situation, try browsing L-com's USB product center for innovative solutions.

 

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.
 

How To Differentiate VGA, SVGA and UXGA

May 8, 2013 at 4:38 PM

 

VGA Cable

While knowing these specific terms is helpful in buying some analog display equipment (such as computer monitors), each refers to the same type of video format. These acronyms relate to the resolution a monitor supports, thus the same type of cabling and connectors are used.

 

Another common denominator with VGA, SVGA, and UXGA is that they are all mostly now legacy. No new products are being built using VGA analog video interfaces. 

 

However, if you have irreplaceable or expensive equipment that requires using VGA analog video, you'll find it useful to know its functionality. 

 

Typical VGA cables have a high-density fifteen-pin (HD15) connector on each end, using a combination of mini-coaxial cables and straight or twisted pair conductors to carry a video signal. VGA does not include audio support like HDMI® and DisplayPort cables do.

 

What do these terms mean? VGA stands for Video Graphics Array. As video display equipment that used the VGA standard became more sophisticated, manufacturers began adjusting the name of the standard to reflect the maximum resolution of the display device. For example, SVGA stands for Super Video Graphics Aray which supports a resolution of 800 x 600. As the list grew, it became easier to just list the maximum resolution rather than the letters that corresponded to it.

 

Today, there are over 20 different letter combinations referring to all sorts of different resolutions, a list of which can be found here. Most of these terms are rarely used to refer to analog video equipment anymore. And as mentioned previously, the standard itself is rapidly becoming legacy in the face of digital video standards such as HDMI®, DVI, and DisplayPort.

 

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