hfeinstein at cox.net
Sun May 7 21:31:08 CDT 2006
Here's a picture of one end of the 802.11 link that I've been working on.
The link uses the WDS bridging technique to link two sites about 1300 feet
apart. One experiment is to see if I can bounce the 2.4Ghz signal off the
belly of a large community water tank that is more or less in line with the
other site. I'm using the Buffalo ML2-G54L airstation for the bridge
and I think it runs 35 millwatts on 2.4Ghz, not really much power. The
antenna visible in the picture is a 15db yagi inside a fiberglass "coke can"
style housing. I've already done some signal profile type testing to see
how the signal is over at the other side of the link. I can at least
form an 802.11 association ("a connection") using a Linksys WRT54GS
(shown in the picture with yagi) and an 802.11G USB plug-in client plugged
into my laptop (with no external antenna) over at the other site. Switching
to the Buffalo bridges and yagi on both sides should bring the signal
to a very usable level. One issue with 802.11 is that
even if there is enough signal to form an association, there may not
be enough signal to reliably move data. Getting 54Mbytes advertised
for 802.11G throughput
is very unlikely unless the bridge or AP is next to the other bridge or
Graphs I've seen show the throughput falling fast with distance.
802.11 will also back-off channel speed until it finds one that the
channel can support.
Other 802.11 networks in the area interfere as well to further reduce
After a walking survey I did with my laptop I found that most other
networks in my area are
on channel 1 and 6 so I put the bridge on channel 11.
One thing about 802.11 in the 2.4Ghz range is that the signal is much
wider than the
the official channel assignment. In fact, the signal is about 5 channels
There are only three "pockets" to use: channel 1,
channel 6 and channel 11.
The wire visible in the picture is the bottom part of a 100 foot 40 meter
random wire I use for CW.
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