Re: Effectiveness of indoor antenna?
- From: Jeff Liebermann <jeffl@xxxxxxxxxxxxxxxxxxxxxx>
- Date: Wed, 29 Jun 2005 08:55:33 -0700
On 29 Jun 2005 01:51:02 -0700, "Chrishow" <chris@xxxxxxxxxxxxxxxxxx>
wrote:
>The building is over three floors, including the attic. Walls are of
>brick construction and the windows are small, leaded lights.
>
>A very rough plan can be seen here -
>www.thejamfactory.eclipse.co.uk/plan.jpg
>
>A picture can be seen here -
>www.thejamfactory.eclipse.co.uk/photo.jpg
Nice house.
I don't think a single wireless access point is going to work. 2.4GHz
does not like water or anything with water in it. Masonry, brick, and
vegetation are full of water to varying degrees. Same with asbestos
or crushed rock in the roofing tiles. 2.4Ghz is not going to
penetrate even one wall, much less the 3 or more required to do this
with a single access point. You're only chance is going through a
window, some of which appear to be clogged with vegetation.
You might have a chance if the interior construction is of light wood
(i.e. pine). 2.4Ghz will go though about 2 such walls. Watch out for
wallpaper with aluminum foil backing.
I scrounged for data on materials attenuation in the past and found:
http://www.thirdbreak.org/pipermail/wireless/2005-June/000804.html
Note that the attenuation for brick varies from 2 to 8 dB depending
upon who did the testing. Apparently, there are some rather drastic
variations in test and construction techniques.
>The distance from office A to office B is approx 25 meters
Looking at the layout, my guess is that you'll be shooting through at
least 2 brick walls (not counting inside walls) no matter the
alignment. Your only chance is if you have a common pair of windows
where each office is directly visible from the other. That doesn't
appear to be the case.
>There may be a straightforward route for some CAT5 caballing, if run
>external to the property. There is already a PABX phone system which
>runs between the rooms, so routing may be simpler than originally
>thought.
>
>I have considered Ethernet over mains, but as it is a very old house,
>the wiring may be separate circuits and I'm certain of the quality.
I've had terrible luck with powerline networking. Too slow and
subject to interference from appliances. On of my friends did that
and found that his connection was comatose when running the laundry
machines.
If you have existing telephone cabling, it might be possible to use
them for ethernet connectivity. I've done this successfully with 25
pair cable at 10baseT (10Mbit/sec) rates. It will NOT work at
100Mbits/sec and all connections must be forced to use 10Mbits/sec.
The catch is that it MUST be dry, good quality, paired cable and is
probably limited to about 25 to 50 meters per run.
I've also done it using 10base2 (Cheapernet) over CATV coax cable.
http://www.multilet.com/us/baseband/product_range/product_range.htm
One run is about 300 meters or RG-6/u.
Topology is somewhat of a nightmare because it must be arranged as a
"star" rather than a "bus". That means all your phone cables and
wires have to come together at one location. That's possible in an
office building, but usually difficult in a home where the phone
wiring is arranged as a bus.
>Thanks for this advice, it makes me even less likely to install a pure
>wireless solution. The last thing I want to do is install a solution
>which is unreliable and will require additional visits to troubleshoot.
It is possible to use wireless through walls and obtain a reliable
system. However, I have some evidence to the contrary. Current, I'm
replacing wireless with wired in approximately 10% of my installations
due to reliability issues. I have an other wiring job to replace
wireless in 2 days. The problem is usually interference from other
wireless users. That may not be an issue here as it appears that
there are no neighbors. Working with desktops is always a problem
because they don't move. A laptop can move around if there are
changing propagation conditions (i.e. moving furniture). That's not
so easy with a desktop. I've found users constantly juggling the
position of their wireless devices to accommodate the latest changes.
A site survey, also known as "try it and see how it works" is fairly
simple. If you have a good solid strong signal throughout the
building, then it will work. If it varies all over the place, then it
probably will be a problem. A fun test is streaming media content
with a small buffer. If the music sounds intermittent and full of
dropouts, so will the data.
>Thanks again for your advice, I'm investigating the structured
>caballing option, with localized AP for individual areas.
That might work if the inside construction is light weight. Good
luck.
--
Jeff Liebermann jeffl@xxxxxxxxxxxxxxxxxxxxxx
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 AE6KS 831-336-2558
.
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