WiFi
Are WiFi routers a health hazard?
With the proliferation of WiFi, it was only going to be a matter of time before health concerns regarding the electromagnetic fields created by WiFi networks would be discussed.
In the United Kingdom, in particular, parent organizations in schools and local health organizations have been questioning the effects WiFi waves may have on children.This is becoming more of an issue, and some parents have even gone as far as suing a school district over plans to install an always-on WiFi network.
At the moment, there isn’t a single study that suggests any harm whatsoever from WiFi networks. Parents, however, say that this is a new technology and it will need long-term studies spanning years to find out.
In the meantime, they want protection for their kids. Some small stories have been popping up in the press across Europe about teachers or workers claiming to have become sick because of WiFi.This follows years of concerns regarding the dangers of cellular electromagnetic fields (phones and towers), which have been studied extensively with mixed results.
At the moment, it is generally agreed that using a mobile phone for long periods can create headaches, possibly ear infections and generally cause a state of nausea for some users.
That’s why it is recommended to use ear pieces, two-way speakers and other solutions whereby you don’t put a phone against your ear for too long.
Accordingly, and due to the fact that WiFi is now becoming widespread – with every home, office and school soon having these WiFi waves flying around- it becomes important to launch scientific studies in the field.
The same people campaigning against mobile phone masts, are the ones suspecting the health impact of wireless computer networks. People defending WiFi say that a WiFi router is really small, use much less power, has a much shorter range, and gives off less radio frequency radiation than an average cell phone tower. Looking at this issue technically reveals that WiFi routers have a peak power output of 100 mW. Compared to most cellphones, which output around 2 W, its makes WiFi look tame.
So far, industry experts and engineers believe that children, and adults, will be perfectly fine in a WiFi covered area, even if they sat straight in front of the wireless router for extended periods.Every electrical appliance in our modern lives emits electromagnetic waves (radiation).
While schools are cracking down on WiFi routers, they’re allowing microwave ovens, cellphones, televisions, portable radios and other electrical devices that may also pose some undefined long-term risk.
Worrying isn’t it? Or maybe there’s nothing to worry about at all. Let’s see some studies that can tell us more. In the meantime, use every electrical gadget or wireless service with moderation and stay tuned!
Written by Written by Zeid Nasser
http://zeidnasser.blogspot.com/2007/04/are-wifi-routers-health-hazard.html
WiFi Antenna properties
An antenna has three main properties: direction, gain and polarization.
Wireless Antenna Gain is term used for measuring of increase in signal power, as decibels (dB). Antenna with a higher gain is more effective in it’s radiation pattern.
Every antenna is designed to raise the power in the wanted direction and reduce it in unwanted directions. Gain of an antenna is reciprocal, meaning it is the same for transmitting and receiving.
Antenna Direction is the shape of the wireless signal after leaving the antenna.
Polarization of the wireless antenna is the orientation of the wireless signal.
It can be vertical, horizontal, circular or combinations of these.
The E-plane and H-plane are reference planes for linearly polarized antenna
This diagram showing the relationship between the E and H planes for a horizontally polarized directional antenna Continue reading →
WiFi Antenna types
Written by: http://www.wifi-antenna.com/
Parabolic grid & dish wireless antenna
This highly directional antenna type transmit/receives signals in a very narrow angle, so they are ideal for long distance and point to point network connections. It has a main reflector surface that is shaped like a paraboloid with an active element at its focus. That way reflector surface can reflect parallel signals to a single focal point. Parabolic wireless antenna are the best choice because very narrow beam-width will provide you withminimum interference with another wireless networks & longest signal distance & faster link
Yagi wireless antenna
A Yagi array wireless antenna is a semi-directional antenna commonly used in wireless communications. Yagi antenna is made from the array of dipoles (elements) parallel to each other exactly the same a s a standard TV rooftop antenna. The first (longest) element in this array is the reflector, second is the driven element and other elements are directors. The more directors the more gain. The are often house in cylinders to protect from the weather.
Omni directional Wifi antenna
This antenna sends and receives signals equally in all directions (360 degrees). Because of that property, this antenna type usually have the lowest gain and is used in point to multipoint links. An omni-directional antenna with an increased gain will increase distance, but decrease it’s effectiveness above and below the antenna, while low-gain type will do the opposite. Imaging the output of a standard supply 2dbi antenna the shape of a doughnut, its circular and fat, as the gain increases the doughnut is flattened out like a pancake to increase its range, this has the downside of losing signal off its low and high points. Again these antenna are housed in a fibre-glass tube to weatherproof.