antenna waste of money?

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antenna  waste of money?

Iv had problems connecting  from a linksys wireless G model WRT54G to
wireless on the 2d floor. I am told extra thick walls prevent it,hence
I don't want to waste money buying linksys HGA7S antennas if it wont
create coverage on the second floor.

ideas? comments?


Re: antenna waste of money?


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Well the answer is a definite "maybe"   Buy them at a retail store and keep
the receipt for a return if necessary.   I have used those antennas at my
house to improve a marginal connection from a 2nd floor WAP11 to the first
floor  (plaster walls, wood floors).   However, at my friend's house the
antennas didn't help much (going through brick walls to exterior patio) and
she was much happier when I replaced her WAP11 + HGA7S combo with a new
Linksys SRX model.    (her reception improved even though she still uses the
standard built in Dell 802.11g card -- a pre-N "SRX" card was not necessary)

-- Paul




Re: antenna waste of money?


Well....maybe.  Sometimes it will help, sometimes it wont.  Depends on the
compistion of the structure

I would recommend, if you can, run an ethernet cable up to the second floor
from the router ethernet ports on the router on the 1st floor.  Get a second
router/Access point and plug in the ethernet cable from the router
downstairs into the second router's internet entry point.  There, now you
have coverage on the 1st and second floors



Re: antenna waste of money?


You may need to position the existing antennas horizontally.
Also take a piece of A5 card fold it at 60 deg, cover it in silver foil and
place it behind and around the antennas, works great for me.
Regards,
Marin



Re: antenna waste of money?



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High gain omni antennas will do nothing for 2nd floor coverage.  Let's
pretend you don't have "extra thick walls".  Antennas do not create
additional RF.  They redirect the RF available from the xmitter and
send it in various directions and patterns as defined by the antenna
construction.  The stock low gain 2dBi Linksys antenna pattern looks
like a donut or torus, with the antenna through the hole in the donut.
I higher gain version of this omni antenna is a flatter and larger
diameter donut.  (The volume of the donut is constant).  You get more
gain at the edge of the donut (perpendicular to the antenna), but you
loose gain in the upwards and downwards directions.  In other words,
the exact opposite of what you're trying to accomplish.  

You can tilt the antenna to a horizontal position, and get much better
up and down coverage, but at the expense of horizontal coverage.  A
good compromise is two high gain antennas, one vertical and one
horizontal.  The catch is that you lose some of the benifits of
diversity reception.

Ideally, what you want is a single directional antenna (patch, panel,
dish, coffee can, whatever) pointed upstairs, and the other port with
a stock omni antenna.  However, that ignores the "extra thick walls"
problem.  What you'll probably see is an ability to connect, but not
be able to stay connected.  That's what signals that bounce around do.
You can probably make this work with a laptop that can be moved
around, but I don't think you want to be moving a desktop every time
someone moves something in the RF path.  If the connection is not
reliable, it's not useable.

I suggest you run a CAT5 cable or use some other method of bridging
the downstairs and upstairs.  HomePNA (phone line networking), telco
cable, power line networking, coax cable, or just run CAT5.


--
Jeff Liebermann    jeffl@comix.santa-cruz.ca.us
150 Felker St #D   http://www.LearnByDestroying.com
Santa Cruz CA 95060    AE6KS  831-336-2558

Re: antenna waste of money?




Jeff Liebermann wrote:
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Jeff, I'm curious about how this works. (2 antennas, 1 pointed up, 1 pointed
horizontal)
When the computer on the same level "talks to" the WRT54G does the antenna
pointed up tend to receive the signal? And when the computer on a different
level "talks to" the WRT54G does the antenna pointed horizontal tend to receive
the signal? I think that is what you are saying. But what happens when the
WRT54G talks back to the computers. Which antenna will it use? Is it smart
enough to use the correct antenna at that moment? And would this smartness vary
if there was traffic from both computers at the same time?



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Re: antenna waste of money?



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It works fairly well.

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Yes.  You used the right words with "tend to".  There's no guarantee
that it will be the preferred antenna.  The way diversity reception
works is that the preferred antenna is one that *LAST* received a
non-corrupted packet.  If data corruption becomes excessive, then the
receiver starts scanning for a better antenna.  It's not instantaneous
and may take a while for the access point to start scanning.

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Probably.  Again, no guarantee.  With the main lobe of the antenna
pattern for a horizontal omni being up and down, it's most likely that
the horizontal antenna will pickup the upstairs signal first (or
better).  Remember, there's little or no RF interaction between the
two antennas.

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Which ever antenna it heard the last non-corrupted packet.  There's no
diversity on transmit.  It simply uses the antenna that was selected
for receive.  However, there are some really old access points that
would do diversity receive, but would only transmit on one antenna.
I'll have to dig through my mess of notes to find the makes and
models.

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No, it's not very smart.  If the "wrong" antenna is initially
selected, it will take a succession of corrupted packets to convince
the access point that it's time to try the other antenna.  If the
signal is sufficiently marginal to be useful, it may never try to
switch until the signal is totally lost.  This is not as horrible as
it may sound because the utility is not for getting the best range or
performance.  Instead, it's for dealing with the all too common
multipath and reflections found in indoor environments.  Reflections
are delays in the signals which can land in between packets.  Instant
data corruption.  Chances are good that the other antenna will NOT be
in the area affected by the same reflections.  So, if the data gets
trashed, it tries another antenna.  Not great, but better than one
antenna.

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Nope.  Diversity antenna selection is by the MAC address, which is by
the connection.  I wish there was a table easily available for which
antenna is selected for which client radio.  However, all that is done
transparently in the RF chipset and does not involve anything in the
MAC controller.  Therefore, not data is available.

Where problems start is if you do something tricky like two
independent antennas and two clients talking to each other.  The
access point has to switch between antennas for every packet.  All
modern chipsets handle this with ease, but older incantations had
problems.  If the traffic is going through the access point, and each
client is on a different antenna, it can slow things down tremendously
with these old access point chipsets.


--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831.336.2558 voice  http://www.LearnByDestroying.com
#                         jeffl@comix.santa-cruz.ca.us
#                           jeffl@cruzio.com     AE6KS

Re: antenna waste of money?




Jeff Liebermann wrote:
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Thanks Jeff for all the info.



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