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
:)