Archived from groups: alt.internet.wireless (
More info?)
On Mon, 27 Sep 2004 15:56:26 GMT, "WINSLIX"
<winslix_nyc@earthlink.net> wrote:
>thank you so much for the info. i take that antenna upgrade is more
>effective than a range extender router.
Maybe. It all depends upon what you are trying to accomplish and what
else you have to work with. Since you haven't disclosed this, I'll
offer some general advice and the inevitable complications.
In most cases, a better antenna will produce an immediate and obvious
improvement while a power amp may not be quite so spectacular.
It's all in the arithmetic. Figure on a +6dB increase in EIRP equal
to double the range. +3dB will buy you 1.4 times the range.
The nice thing about higher gain antennas is that the benefits appear
in both transmit and receive. Simply adding a more powerful
transmitter only has an effect in one direction. In order to profit
from such an arrangement, one would need to add an amplifier at both
ends of a link. Some cheapo amplifiers are fixed gain. That means
that your access point and coax cable loss has to be EXACTLY what the
manufactory specifies, or you will either end up with no tx signal, or
overdrive which mangles the modulation. A 1 watt (+30dBm) power
amplifier will offer about +15dB gain in the transmit direction.
Sounds great until you consider that the best the receive amplifier
can do is compensate for the coax loss. Unless the other end of the
link also has a 1 watt amplifier, such an arrangement tends to be
asymmetrical. (It's called an alligator. Big mouth, small ears).
Some of the later access points appear to have both improved
sensitivity and more power output. The Senao based access points are
a good example. Compared to the generic bottom of the line access
points and cards, the receivers are about 3dB more sensitive, while
the transmitters belch about 8dB more power output. That's good for a
substantial improvement in range by itself. If a better antenna is
not in the plans, a better access point might be a better choice.
A decent omni antenna will usually be 6dBi or 8dBi gain. That's good
for double the range (assuming minimal coax loss). It also tends to
be located in better and higher locations. If directional antennas
are a possibility, the gains range from 8dBi (patch) to 24dBi (dish).
The problem with the higher gain antennas is that they have a fairly
narrow beam width. You can easily end up shooting over everyone's
head, or missing a large enough target area.
Tower or pole top amplifiers do have a purpose. They largely
eliminate the effects of coax cable loss. I prefer mounting the
access point on top of the tower and running it via PoE CAT5 instead
of coax. However, if you wanna run long and cable runs, an amplifier
is a tolerable idea. Prices are rather high for these. The only
problem with a pole top access point is that it tends to fail in the
middle of the night, during a storm, when I'm trying to sleep, etc...
--
Jeff Liebermann jeffl@comix.santa-cruz.ca.us
150 Felker St #D
http://www.LearnByDestroying.com
Santa Cruz CA 95060 AE6KS 831-336-2558
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