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Wireless LAN
- To: <ukha_d@xxxxxxx>
- Subject: Wireless LAN
- From: "Mark McCall" <mark@xxxxxxx>
- Date: Mon, 18 Dec 2000 15:48:01 -0000
- Delivered-to: rich@xxxxxxx
- Delivered-to: mailing list ukha_d@xxxxxxx
- Mailing-list: list ukha_d@xxxxxxx; contact
ukha_d-owner@xxxxxxx
- Reply-to: ukha_d@xxxxxxx
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
:)
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