Re: [MH-list] wi fi aerial


Reg <lists.reg@...>
 

On 1 December 2012 17:30, peter norton, <stbrelades@talktalk.net> wrote:

Has anyone tried any of the WiFi aerials to increase the range of
receiving "free" connections, such as those offered by Mac D's ?
They seem to range in price from £25 to £100 and be either directional or
omni-directional.
And will they work on an Android tablet such as an Arsus ? Spelling
intentional.
Having spent a good amount on a supposedly good TV aerial for UK use, and
found it a total waste of time ( I actually opened the stream-lined casing
to find it was virtually empty apart from an alloy strip around the edge ),
I hesitate to waste more money without recommendation.
Recently, using the E-Pad inside a motorway station I found I had to be
virtually in the hamburger queue to get a decent signal.
It would be nice if parking outside could work.
Peter there are two basic things to consider. The 'radio' and the
'antenna' in your device - Android, PC etc.

The radio sends and receives the signal to and from the Wi-Fi point,
which incorporates a similar radio and antenna. You have no control
over the Wi-Fi point (other than changing your position), so to
improve your connection, you have to improve what you use in or
attached to your device.

The radio sends at a certain power level and the antenna will amplify
or reduce the power sent to the Wi-Fi point.

So to the output power of the radio, you add or subtract the gain of
the antenna and subtract the losses in the air between your position
and that of the point. Increase the distance between you and the
point and that will increase the losses in the air.

The gain of an antenna is normally measured in dB - decibel. This has
no units as it is a ratio. If the antenna gain doubles the strength
of the signal, then it's gain is 3 dB. Normally the gain of 0 dB,
(the standard reference value) is the gain of a standard dipole
antenna.

The gain of a directional antenna should be greater than 0 dB, but as
you write it's possible to waste your money on false claims! A
directional antenna is designed to focus the signal into a narrow
beam, much like a light torch.

A dipole has a directivity chart similar to a figure 8 with the two
peaks at the top and bottom of the 8, which aligns at right angles to
the straight line of the antenna, which is two rods insulated in the
middle.

A good external omni-directional antenna has a gain of about -2 dB or
a loss. But it depends on it's design. In 3-D the chart resembles a
doughnut in shape.

In a small device like a small tablet, the gain (loss) would be -3 dB
or more due to the construction. The direction of best gain can be
found by rotating the device and finding the best way to point it
relative to the point. The antenna will be under one outer surface
(edge or flat surface) and where you hold the device can also have an
effect. Not a true omni-directional antenna as it's pattern is not
the same in all directions.

In a directional antenna the gain can be improved by good design and
materials, but there is a practical limit. As the gain increases the
beam angle gets smaller (much like Sat TV dishes) and this makes it
more difficult to align with the point.

A warning. Some unscrupulousness dealers will describe the gain of
their antenna in dBi. This is a reference to a 'theoretical point'
(Not 'point' as here used for Wi-Fi point) in space.

2.14 dBi is the same as 0 dB, so be careful.

Now to consider your device. It must have a special antenna socket
and most don't. Or use a USB stick or cable to connect to your device
and then the operating system must support the USB product that will
contain the radio and the antenna.

Reg.

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