[kismac] Re: Wireless Card
- From: Brad Knowles <brad.knowles@xxxxxxxxx>
- To: kismac@xxxxxxxxxxxxx
- Date: Fri, 23 Jul 2004 12:40:14 +0200
At 6:14 AM -0400 2004-07-23, Erik Winkler wrote:
Recommend Orinoco Gold Classic card. Just found one at emicrox
(http://www.emicrox.com/eShop/product.aspx?advanced=1&cid=10011&attr=Wireless+Networking&pid=844654)
for $41.95 US.
Note that the Orinoco cards top out at 30mW/15dB power, whereas
the Senao NL/SL-2511CDPLUS is 200mW/23dB. So, that 6dB gain you get
with the indoor Yagi antenna only takes you up to 21dB of power,
which is still less than the Senao. Of course, Senao has models
which allow you to attach external antennas (NL/SL-2511CDPLUS EXT2),
so you can get further gains as well. The advantage (or
disadvantage) that a Yagi antenna would have here is the extreme
directionality of the signal.
Of course, all of this has to stay under the government-mandated
EIRP power limits, too.
Now, you also need to keep in mind sensitivity, as well as power.
The Senao is one of the most sensitive cards on the market, at
-95/-93/-91/-89 (dBm signal/noise ratios at 1Mbps, 2Mbps, 5.5Mbps,
and 11Mbps respectively), whereas the Lucent/Agere/Proxim Orinoco
Gold/Silver Card (32mW) is -94/-91/-87/-82, and "... a 3 dB
difference is double the power ...".
Also note:
The difference between a Cisco 350 and a Addtron at 1 Mbps is
32x times the sensitivity. This means that the Cisco needs 1/32
as much signal strength as the Addtron does to work at the same
rate. Also, a lower receive sensitivity number is better (IE:
-95 is better than -80).
So, the Senao isn't that much more sensitive at the slower rates
(only 1dB at 1Mbps and 2dB at 2Mbps), but at 5.5Mbps it is more than
twice as sensitive (4dB), and at 11Mbps it is more than four times as
sensitive (7dB).
If you have power but not sensitivity, that means that there
would be stations out there that can receive your signals fine, but
you can't see theirs. This would obviously limit your distance you
can travel way from the other devices.
--
Brad Knowles, <brad.knowles@xxxxxxxxx>
"Those who would give up essential Liberty, to purchase a little
temporary Safety, deserve neither Liberty nor Safety."
-- Benjamin Franklin (1706-1790), reply of the Pennsylvania
Assembly to the Governor, November 11, 1755
SAGE member since 1995. See <http://www.sage.org/> for more info.
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