"Scott Nelson" <(E-Mail Removed)> wrote:
>For a Linksys wrt54g with stock/factory antenna's, what would messing with
>these settings do for me?
Depends.
>What situation(s) would setting, say, the left for transmit and the right to
>receive do for me?
Anything from totally mess everything up, to nothing... depending.
>If settings were kept in default "auto" mode for both antenna's, I "assume"
>that both antenna's do tx/rx correct?
Yes, but only one antenna at a time, and only transmit or receive
at one time... and on which antenna, again depends.
If you starting to get the idea this *all* depends... It *does!*
(And eventually, after all of these comments, I'll try to explain
some of it.)
>If so, would orientating one antenna horizontally and the other vertically
>help get more area, assuming the above puts the unit in some sort of
>"diversity" mode?
Depends.
>Would dedicating them to a single function help anything for me using stock
>antenna's?
Depends.
>I do have the 7dBi Linksys antenna's that I am going to put on the wrt54g
>after my testing is done so I can reduce the power on my wrt54g so, that
>might help keep the heat down a little.
Probably not though. Think about that for a minute. If you crank it
all the way up, that's 255 mW of power, or 1/4 of a Watt. If that chip
is only 25% efficient, that means it is dissipating 3/4 of a Watt.
So reduce the power all the way down to the default 28 mW, and
if that chip is still only 25% efficient, the chip will be using
112 mW of power, 28 wW will be RF output, and 84 mW will be
heat. So you've changed the heat dissipation from .750 W to
..084 W, or a reduction of 2/3rds of a Watt. 2/3rds of a Watt
isn't what's heating up the box... and if you reduce the
standard 28 mW, you obviously won't get anything close to any
2/3rds of a Watt reduction.
>Anyone using anything other than "auto" ? If so, for what kind of
>application?
>More curiosity then anything else.
I have a wrt54g that has a single antenna, and of course both tx
and rx are locked to that one (if you do that, use the antenna
socket nearest the power socket, as it has a much shorter
connection inside the box).
>Environment:
>I have a 5 story brick building with six unit's/flat's/condo's per floor and
>have an elevator shaft smack dab in the middle of building.
>So, what I have so far is:
>
>- 1st floor elevator left side of shaft a wap55ag (ch6) and on the left side
>a wrt54g (ch1)( both external to the elevator shaft )
>- 3rd floor hall a wre54g repeater (ch6) on same side of elevator shaft as
>wrt54g ( externally of course ) doing WDS with wrt54g
>- 6th floor ( roofdeck) a wap55ag (ch11)
As I'll explain down a ways, you might be better off moving the
1st Floor units to the 2nd floor, and the 3rd Floor units to the
5th floor. Hopefully (you'll have to test and see), each unit
can cover one floor above and one floor below. The question is,
will it go through the roof, and do you need that unit at all.
>wrt54g ver3 running Firmware Version: v3.03.6 - HyperWRT 2.1b1 - not using
>wan port/router
>wap55ag ver2 running Firmware Version: 1.1 - factory
>
>Now, scenario above "seems" to get decent coverage all over the building
>with this setup so far.
>I have been playing around with the settings on the wrt54g though always
>trying to get the best coverage I can get by adjusting antenna orientation,
>etc, AP placement, etc.
>As of now, I have all of the AP antenna's orientation vertically.
Since you are going up and down, horizontal polarization might
be better, depending... if there is any location where you can
point the two ends of the antenna toward areas that will never
be used by a client, it will be better. That is particularly true
because you are using one unit in the center of each floor.
An example that does not fit your situation, but which might
illustrate the point, would be one large rectangular room with
two AP's. If they are located about 1/3rd of the way into the
room from each end, perhaps vertical polarization would be best.
I they are at the ends of the room, horizontal polarization
would be better (especially if a reflector could be added to
bounce what would go out the wall back into the room).
Think about the "donut" shaped pattern around an antenna, and
see if that makes sense. If it doesn't (for example if the idea
of a "donut" shaped pattern doesn't ring a bell), just say so
and I'll let Jeff Liebermann try explaining it! :-)
>Would ( for the wrt54g ) setting one of the antenna's vertical and the other
>horizontal help me?
>I have done walk tests with NetStumbler and haven't seen any huge gains with
>different antenna orientation but, thought I would double check myself with
>ya'll on what ya'll have seen/experienced.
>Does my thinking make sense above or am I over/under thinking something?
Wow! You've got a *lot* of stuff that this depends on!
First off, lets understand what those antennas are doing and how
they are switched, so that you can get a better idea of the
effect of any given configuration.
Either the transmitter or the receiver, connects to one or the
other of the antennas. When a receiver is connected, it will
switch antennas at regular intervals (whether it is receiving a
signal or not), looking for the best signal. Hence if you have
two very different antennas, it will eventually pick the best
one for any given signal.
But the transmit *always* starts with the antenna last used to
receive. That assumes it will also be the best signal, but it
just ain't necessarily so! Lets say you have two highly
directional antennas, one pointed north and one pointed south.
If a client to the south transmits, it may take a bit, but the
receiver will eventually pick the south antenna and will see the
signal. At that point, no signal from the north will be
received until at least the interval it takes to test the other
antenna, so a second client to the north is going to wait much
longer to connect than would another client to the south.
Worse though, is if the receiver is seeing a steady signal from
south (somebody doing a big file transfer for example), and a
packet of data needs to be sent to a north client. The
transmitter will *always* use the last antenna used for receive,
which in this case is *always* going to be the south antenna.
The north client will *never* see it, until it happens to
transmit something itself and cause the north antenna to be
switched on for receive.
Which is to say, except for point-to-point links, you may want
only antennas that are very nearly the same. If you have only
one client, and that client roams widely, then the increase
coverage would be fine, and there would be little effect from
switching disparate antennas. But if this is an office building
or an hotel, and there might be many users connected over this
wide coverage, disparate antennas being switched might cause
them significant annoyance.
That applies to polarization in ideal situations, but less
so in real situations. In your case, the amount of multipath
from various reflecting surfaces is almost certain to cause
polarization of received signals to be all over the map.
Specifically, since you are getting good coverage, you obviously
have a workable configuration! The only thing I'd suggest is
checking to see if that rooftop unit really needs to be on the
roof. On the roof it probably only provides coverage for one
floor below. But if you put it one the top floor, will it then
cover the roof, the top floor, and the next one down? If so, you
get three floors with one unit, and you might lessen the amount
of off premise exposure too. Of course, if the roof is metal,
that won't work...
--
Floyd L. Davidson <http://web.newsguy.com/floyd_davidson>
Ukpeagvik (Barrow, Alaska)
(E-Mail Removed)
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