antenna question

[necro702]

I see some wireless routers have 2 antennas and others only have one. Will
it help if I get a router with 2 antennas like the dlink 614+ or will it not really
make too much difference?

thx

 

[ScottMac]

It may help, depending on the immediate environment. The dual antennas ("diversity") are there to reduce an effect where, at certain parts of the radio wave, the signal is reduced to near zero (a "null"). By using two antennas, properly spaced, when the signal from one antenna is at a null, the other antenna is receiving the signal at/near full possible strength (given the distance and power output).

The null effect can be more pronounced when reflected portions of the radio signal interfere with the primary signal (multipath). I believe that in most (if not all) implementations, only one antenna is active at a time, with bias given to the antenna that is receiving the specific signal at the highest quality (something like that).

If your environment is not too multipath-ridden, and the computer is not moving around much, then a diversity antenna system is not going to be of much use. At 2.4 Gig, you're looking at a wavelength of ~ 8" or so (with a null on the half-wave - ~4").

ktwebb is da man for wireless; I'm sure he'll get around to filling in the gaps in the explaination....

FWIW

Scott

 

[ktwebb]

Can't add much to that. The benefits of spatial diversity using two equal omni antennas vary wildy from environment to environment. If you have multipath interfernce in yours, then having two dipoles on your AP can be significant. AP placement, more specifically your antenna placement, will be the biggest factor in determining that. At it's most significant, diversity antennas can help signal fading a good bit. For what it's worth, at home I use a SOHO speedstream AP/Router combo with a single dipole, albeit 5 dBi vs the usual 2.2. While a flatter pattern, the coverage is pretty impressive.