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Technical Discussions => Networking/Web => Topic started by: madman on August 07, 2009, 05:58:56 PM

Title: A Few Questions About High Gain Omnidirectional Antennae
Post by: madman on August 07, 2009, 05:58:56 PM
I was thinking of getting this to widen my WiFi range in the house.  My intention to is get a better WiFi signal whether I'm in the first floor or the second floor.  I have a Linksys WRT54GS, which is on the second floor.

Which of the branded antennae are any good?  Where would they be locally available?  What would be the price range?  Any specs that I should look for, e.g. 8 dBi, 9 dBi, 15 dBi?

Are the CDR King high gain antennae worth considering?  I don't intend naman to supply the whole neighborhood with a WiFi signal, but just the two floors of our house.

And considering that my WRT54GS has two stock antennae, should I buy two high-gain replacements?  Would there be any advantage in replacing both stock antennae with high gain ones?  Or would one suffice?  If one will be enough, do I disconnect the other stock antenna or keep it on?  And if I use just one, which do I replace, the right antenna or the left?  Or does it matter?

I'd make a cantenna, but I want one that's omnidirectional.  So, the cantenna's out of the question.

Oh, one more question: am I correct in thinking that the Linksys WRT54GS uses R-TNC antenna connectors?

Hope somebody can help.
Title: Re: A Few Questions About High Gain Omnidirectional Antennae
Post by: motion55 on August 07, 2009, 06:51:33 PM
A high gain omnidirectional antenna gets its extra power by flattening the radiation field. The high gain omni antenna throws a signal a farther signal perpendicular to its axis, but weakening it above or below the antenna. 


So putting a high gain antenna weakens your coverage to the floor above or below the wireless AP.

As what to do with two antennae:

The linksys wifi router (non mimo) has an RF switch that selects which antenna gets the better signal and automatically switches to that. Only one antenna at a time is being used. I don't know how fast the antenna is being switched. In other words, whether it is fast enough to switch between different client PCs or fixed pa rin to one antenna as the AP is communicating with different PCs.

I would recommend to orient the antennas tilted slightly with respect to each other to give a diverse radiation field. One antenna can have a high gain omni to benefit PCs on the same floor and a lower gain but fatter radiation field to benefit PCs on the other floors.

I would like to add that all antennae sacrifice coverage to get a higher gain. An antenna with a uniform coverage is called an isotropic antenna. All other antennae gains are always compared to this isotropic antenna. The antenna gain is in dBi or gain compared to an isotropic antenna.