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Are those wifi antenna's on ebay any good?
PowerJC
Posts: 1,038 Forum Member
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I've seen quite a few of these on ebay promising 12db gain etc, but do they actually help improve the signal? They just look like normal antenna's but bigger. Also are they legal, i.e. not pushing the wifi signal above the safe limit?
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Some of these 2.4GHz antennas say they will boost the signal in terms of dB, or sometimes dBi. If they say they will boost to 12dB, they will mean to a maximum of 1.6 watts (each 3dB is double - so 9dB would be 800mW).
dBi is slightly more than dB, but not that much more (2.15dBi over the dB figure. So 14.15dBi is 12dB, but 12dBi is 9.85dB).
Technically anything over 100mW is not permitted, but I'm not exactly sure whether that is for freely radiating in all directions, or for any power over 100mW directed at a specific location. The antennas you have been looking at will be omni-directional rather than directional - so will radiated out in all directions. Some of the diy ones are directional, so a wi-fi signal would only be beamed in one direction (sometimes as little as 15-20 degrees beam width from the antenna). The main concern is using too much power will mean problems for everyone else using wi-fi & bluetooth and all the other 2.4GHz equipment. Using a directional antenna would mean no signal reaching those out of the beam at all (ie those 320-340 degrees out of beam).
think of them as a lens. if you buy the right kind it can direct the signal where it needs to go. it won't magically boost the power.
theres also the matter of the antenna on your pc/laptop