Interesting stuff on how Tim Morris is getting on with his wireless
LAN....
>I'm getting closer on the Wireless LANs. I know
you're
>interested, so just
>to fill you in on
where
I've got to:
>
>The Compaq cards have a big
advantage over and above the rest of
>the world,
>it
that the PCI cards are a lot cheaper than all their competitors
cards
>with 128 bit encryption. (£125 vs £200).
>
>The problem they have (and all of them have), is that
radio
>waves really do
>not like passing through
the
metal cabinet of the PC, so it restricts the
>radio waves
propogating from 360 to 180 degrees horizontally - vertical
>propogation is around 75 degrees. The majors (Cisco, 3Com,
>Lucent - which is
>also sold under the Evansys brand at
around the same price) all sell an
>external antenna, but
Compaq
do not.
>
>To compound matters they use a
proprietary connector on the board. I've
>learned a lot about
RF
connectors in the past week, and it is an SMA
>(subminature
BNC
but with a screw thread, instead of a bayonet) connector
>with
a
left hand thread. I've fired emails all over the shop, and none
of
>the major connector suppliers make anything to mate with it. The
industry
>standard for Access Points (the best way to think of
an
Access Point is a
>wireless hub, with an interface to wired
networks) is Reverse
>Polarity TNC -
>BNC with a
thread. The reverse polarity bit is designed for all microwave
>antennae, to stop people interchanging HF and microwave
antenna.
>Certainly
>Cisco use reverse polarity SMA on their
boards.
>
>Cisco make two antennae that I'm
looking
into one at £122, and
>one at £65.
>Both have two
elements to increase coverage. The more expensive
>one has
two
>7 inch antennae which can be angled to suit, the cheaper
has
two fixed
>antennae angled in a V at about 70 degrees. This
gives
pretty
>good coverage.
>There is a null zone in a
30
degree cone, above and below it,
>but it should
>offer coverage out to 300 feet in building at 11 Mbits. The
only
>drawback is
>that it comes with a 1 foot cable - which is
a
total waste. I'm going to
>order a couple tomorrow, plus the
relevant bits to make some extension
>cables (I'll wire the
cables directly in to the antenna
>providing the
test
>goes OK - joints tend to reduce the signal strength). I'll also order
the
>relevant (SMA Rev Pol) connector to go on to the PCI
card,
>desolder the one
>that is on there and put
it
in a draw just in case of warranty (3 years)
>claims.
>
>The costs are adding up, it can be cheaper if you go for
40
bit
>encryption,
>but I'm actually going between
two
buildings, so it is still cheaper than
>getting someone to dig
a
50-60 foot trench and lay cable in a
>conduit - or
>if you are that way inclined, less time consuming than doing
it
>yourself :)