Scott / Jeff,
Never heard of this. I know our access points each have two antennas,
and they can be disconnected and replaced with more appropriate units to
give the best coverage.
Access points (prior to 802.11pre-N) typically had two antenna connectors.
Replacing the default stub antennas with higher gain antennas can
dramatically increase the range. But you would typically want to do this to
BOTH antenna connectors because the reason it has two is because it uses a
technique called "antenna diversity" which achieves better (i.e. most
consistent) reception than you can get with a single antenna. Some later
model 802.11G access points also use a thing called MIMO (Multiple In,
Multiple Out) which gives even better coverage when all else is equal (same
location, same antennas, etc).
All the 802.11 pre-N access points I have seen actually use three antennas
instead of two. I'm told that the pre-N stuff gets dramatically better
coverage even when connecting with 802.11g clients. So it may well be worth
the nominal extra cost to use pre-N access points even if all the handhelds
will be 802.11G hardware.
But, I haven't heard of having a central access
point that powers many antennas before...
I don't see how you could do this cost effectively. A major factor in
reception when using an external antenna is the signal loss on the cable
lead between the antenna(s) and the access point. If you are going more
than a couple of feet, you really want to be using a lower-loss lead and
they are very spendy. You'd quickly pay more for the cable then you would
additional access points. It is far better (and cheaper) to mount the
access point very near the external antenna, using a weatherproof box if
necessary, and just run the CAT5 to it and use POE to power the access
point. Then a short cable to the antenna. If it goes outdoors at all, also
consider surge protection.
Using MIMO diversity receivers and higher gain antennas can minimize how
many access points you'll need. But everything depends on your environment,
how tall your racking is compared to the height of the antennas, the
composition of the racking and products shelved, etc. I also would highly
recommend a qualified person do a site survey, unless you have lots of
headroom in the warehouse and can mount the APs with few obstructions. Bear
in mind that to a radio signal, "line of sight" does not refer to just a
clear path like a laser beam, but also includes the "fresnel zone", the
width of which varies by RF frequency and distance.
Doug
midrange.com
