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Written by alex
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Tuesday, 07 April 2009 14:44 |
Antennas are the mussles of the wifi , the better they are wifi will work better.
The one of the most important thing to know about antennas are the polarisations there is VERTICAL polarisation and HORIZONTAL polarisation.In oreder to work properly the tu antenas that communicate should on the same polarisation it can work with diffrent but the performance are cut to half.The mosta antennas u can make ur self but some are sofisticated and cant be made by hand.There are 3 types of antennas
*Omni also known as Omni-directional
*Directional
*Sector
Lets start with omni antennas:
Omni antennas cover the 360dg radius.So they have weak directioning and with these antennas u cant go to long distances , they are used for hotspot because of theirs 360dg coverdge.
Omni Antenna 9Dbi
There are warious Omni antennas (ranked by power) they al are the same standard but difrent power most commonly there are 9Dbi,12Dbi,15,Dbi omni antennas.
So whats the diffrent ? What do we get with more stronger antena?
With more Dbi`s u have wider radius of covredge but lesser speed , but the speed variations betwene antenas are small.The way to go is 12 dbi antennas (mine opinion).So can u make omni antena?No u cant there are sofisticadet there were attempts making them and manuals some antenas made by hand proved well on the B standard but on the g wery bad so i suggest buying it or use sector antennas.
Omni Antenna Patterns (8dBi)
So lets go to direcitonal anetnnas:
There are many many models of this kind of antennas so ill write about most common and most well performed antennas:
Weel Start with the:
*Biquad Antenna
The biquad antenna is home made i thing there arent any manufactures who make them?Why it is simple to make them.
http://martybugs.net/wireless/biquad/ -Making the biquad antenna
Biquad Antenna
Ok what are performanses of the biquad , wery well it has a power about 15dBi`s and on the g standard i think it was the most common antena , easy to make dont need more then 10$ for material.But on the g standard it didnt prove so well it was just weak for the g.For the g 10-15dBi gain wasent enough, then Mr.Trevor Marshall (www.trevormarshall.com) took sattelite Dish and put the biquad as feed
Trevor Marshall`s Biquad on Primestar Dish
So with more preciset directioning the gain is bigger now with dish u have 20-30dBi gain antenna
Biquad Graph
Biquad On As a Feed on the dish
Deniro(Bgwireless) With his Homemade Biquad+Dish
http://martybugs.net/wireless/biquad/double.cgi -Double biquad Antenna
*3D Corner antenna
This is the most common 5.8Ghz antenna , the performances are great and its easy to make as biquad it is commonly used as a feed on the dish
3D corner Antenna
http://www.remcom.com/examples/xgtdexampleDetailUpdated.php?exampleID=81&thisProduct=XGTD -making the 3d corner antenna
3D corner Antenna as a feed on Dish By Spider&Pota(Bgwireless)
Lets go now to Grid Antennas
*GriD
The grid is one of the most respected wifi antennas , it is comoonly bought and it is not expensive but the performances and gain of the antenna is great.It is not homemade nobody tried to make it...The grid antenna has about warious gains depending from the models most commons are 15dBi , 20dBi and 24dbi
There are both 2.4ghz and 5.8Ghz grid antennas
Grid Antenna , 2.4Ghz band
Grid Antenna , 5.8Ghz band
Thats about it (about directional antennas) as i said there warious directional antennas (yagi , helix , pannel...)and i writed about most common and well performed antennas
*Sector Antennas
Ok sector antennas are used for ap`s in access point mode , the usage is simmilar to omni antennas but they dont have radius of 360dg they have commonly 180dg but there also sectors with 360 dg (eg. omnidirectional slotet wguide) radius.Ill write about two types of sector antennas:
Sloted Waveguide a.k.a. Trevor Marshall antenna
Amos (works on the Frenklin`s anttenna pricipe)
So lets go to Sloted Waveguides
Its really simple antenna and has great performanses.
Sloted Waveguide by Trevor Marshall
So u see on the picture it is a peace of aluminium with 8 or 16 wholes that acts as a dipoles.There can bi 8hole slotes waveguide an 16hole first one has a gain aboun 8-10 dBi`s and secound abou 15dBi`s it deppends how precise are u when making it
the easiest way to make it is the CNC machine if u have it just go to
http://trevormarshall.com/waveguides.htm and follow the instructions.
These $ pictures is Omnidirectional Sloted Waveguide made & puted on the roof by Eddie & Me and friends :D
The Top Of the Sloted Waveguide
Eddie Attaching N connector to the Antenna (on the roof)
Attaching the antena an the stick to the roof (Eddie & Dotla)
Up and Runing
From my expirience sloted wave guides are great antannas and now a more better antena and simple to make (not easy , simple!)
Amos Antenna
This antenna is wery powerfull and realy if u can make it right can give great results
Amos Antenna
The amos antena is in fact the Franklin`s antenna but for 2.4ghz.U ask what is that?
Thats an antena principe or designe it can work on al frequencies ?huh how?
The Main thing is in antenna dipole , the bigger dipole it is the smaller frequensy the smaller dipole the bigger frequensies.That is the problem to make for e.g amos for 5.8 ghz the antenna is to small!
www.qsl.net/yu1aw/ANT.htm > Making The Amos Antenna by Dragoslav Dobricic
there are two types of amos antennas:
Regular Amos & Inverted amos
Inverted Amos has inverted dipoles with better performanses
For more info chek the Dragoslav`s page
Here Are Some Pictures Of Amos Antennas:
Inverted Amos7 Antennas made by NYC&Pota(Bgwireless)
Inverted Amos7 Antennas made by NYC&Pota(Bgwireless)
Great Job On These Antennas Guys!Not NyC just Pota i dont like him :D just kidn
Thais Is The most default antennas that use wifi... Hope u liked my article :D
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