On Fri, Apr 08, 2005 at 12:04:25PM +1000, Terry Collins wrote:
> Phil Scarratt wrote:
> > 
> > Hey
> > 
> > Just googling at the moment for it at the moment...does anyone know if
> > you can have multiple aerials/antennas on a wireless access point? 
> 
> No!.

Huh? You most certainly can.

Whether it is at all practical is a totally different matter.

First off, many APs support diversity, that is, two antennas. Generally
only one will transmit, while a switch switches between the antenna with
the highest signal strength for receive. However, this only works with
the two antennas being close to each other and relatively omnidirectional.

If you were to put the antennas in a fashion that they were unable to see
each other, but able to see different wireless nodes, your AP would reduce
performance to almost non-existant, crazily switching between antennas,
and dealing with massive error.

Another way, which has potential, is to use just a single antenna port from
the AP (obviously the one with TX if it's diversity equipped), connect it
to a 2.4GHz splitter/combiner, and run coax from there to two antennas.
This could conceivably allow radio signal from two areas previously blind
to each other to propogate to the AP. Just remember, a 2 port Splitter/
Combiner has a theoretical signal loss of 3dB, due to splitting the signal
into two, and there's probably <0.5dB loss to add to that for insertion
loss of the device. Another factor to consider would be the loss from the
runs of coaxial cable.

So once you've calculated a system power budget for the two antenna system,
and also a financial budget to acheive that particular power budget, you
can assess whether or not, it is viable to do at all.

Hope this helps somewhat answer the question, without getting too far into
the nitty gritty of radcomms engineering.


Regards,

Jon
 
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