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Old 02-26-2009, 09:44 PM
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Default Best Wireless router Signal Ratio Strength

Hi guys!

I bought a new Linksys WRT54GS Router and Installed in my home Network.

It has 13 Different Channels.

I want to select the Best of Channels to have Very Strong Signal For My Devices.

I Have Install a D-Link Wireless PCI Card On My XP Machine and Installed `WirelessMon` Software to check the Signal Strength. These Pictures below are my signal Strength Ratio in dBm Values in Channel (1) and channel (13) of My Router.

Signal Strength in Channel (1) = -40 dBm
Signal Strength in Channel (13) = -32 dBm















My Question Is:

Which Negative Value Is Good and Strong To Cover My Home Wireless Devices? -40dBm or -32dBm

Last edited by mkmmkm; 02-26-2009 at 09:47 PM..
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Old 02-28-2009, 09:53 AM
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Default

-32dB(m) - in short.

The closer to 0 the negative figure is, the stronger the signal is. For every 3db(m) change in signal strength, the signal strength doubles - or increases by 100%

So, -32 is 8db stronger than - 40, and that 8db is equal to 100% stronger (3db), plus 100% stronger again (another 3db), plus 66% stronger again (the remaining 2db = 2/3 of 100% = 66%) - a total of 266% stronger.

There is something else that you need to keep in mind - it is SNR, or the Signal to Noise Ratio. If your software displays a SNR figure, the stronger channel may not be the channel with the higher (or closer to 0 db) figure. Indeed the stronger channel which will give you faster transfer speeds, is quite often often the one which has a better SNR figure.

A better SNR figure is one in which the difference between the Signal figure and Noise figure is largest e.g. An SNR of -32/-32 can give you a much slower tansfer speed than an SNR of -32/-40.

Why?
because as can be seen the Noise figure (the 2nd figure) is closer to 0 than the first figure - in other words: firstly, it is stronger, and secondly, the differance between the first pair 2 figures is less than the differance between the 2nd pair of figures. The stronger the signal figure is relative to the noise figure, the better/faster your transfer rates will be. It is not just the strength of the signal, it is its relation to the noise figure that is just as, if not more important.

... and in terms of milliwatts:

-40 dBm = 0.0001 milli watts

-32 dBm = 0.0006 milli watts


Take a look at the following webpage - it relates to db to milliwatts.

dBm to mW Conversion Calculator

Lastly - the db levels displayed by wifi card software are almost always hopelessly inaccurate - way way off the true/accurate figure. They are given for a single moment in time - a split second. The actual real-world signal consistantly flucuates. pay little attention to the figure given by the software, other than for been a relative indication of strengths between different channels - thats all they are good for.

Last edited by RFPOWER; 02-28-2009 at 10:03 AM..
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