Broadband
to Broadwater Tower
On April
2, 2002, we installed two radios at Broadwater Tower; first the
Wi-Lan 900 MHz backhaul, and then the first of Hog Island's two
Zcomax 802.11b access points.
The 900 MHz
Wi-Lan backhaul was set up using 13 dBi directional (Yagi) antennas
detailed in Diary 39. The connection is robust, at least in terms
of signal strength. So far there have been no reports of downtime
due to signal interference by weather. However wind, which is fairly
constant at the top of Broadwater Tower, caused the Yagi to oscillate
like an accordion reed, bouncing up and down about 6 times per second.
We not-too-coincidentally
experienced about 20% dropped packets. The antenna oscillation was
stopped by running thin rope from the antenna diagonally to the
railing, thus dampening the vibration and solving the dropped packet
problem.
Dampening system for a Yagi in the wind.
Birds
As this is
a Nature Conservancy site, an ongoing issue is the health and well-being
of the local bird population. There have been two species of particular
interest to us at Broadwater: Peregrine falcons and barn owls. The
Peregrine is endangered, and thus understandably afforded every
courtesy in that once a Peregrine begins to nest, we are required
to stay away from the tower. Rules are a little more relaxed in
the case of owls, although direct interference with their lifestyle
would still be discouraged.
A
Peregrine falcon on Hog Island
Since the
Peregrines, if they are going to nest, generally do so by mid-April,
that became our drop-dead date for setup of the Broadwater Tower
hardware. If we could not complete the job by then, there was no
guarantee we could return to the tower until fall of 2002, after
the grant program was over.
As it turns
out, we had plenty of time: the owls, bigger than Peregrines, moved
in and made sure no Peregrines would nest, thus obviating the April
time limit. The only downside was/is that it became necessary for
visitors to the tower to wear headgear, not only for the risk of
falling, but also to protect from the mother owl.
Equipment
List The following equipment was installed at Broadwater Tower:
- Power-related
(provided by UVA):
- Batteries
(2)
- Solar
Panels, 50-watt (6)
- ProStar-30
charge control unit (made by Morningstar)
- Radios
- Wi-Lan
900 MHz radio
- 900
MHz 13 dBi directional (Yagi) antenna
- Zcomax
XI-1000 802.11b Access Point (with pigtail)
- Teletronics
500mw Indoor 2.4GHz Amplifier
- 8
dBi omnidirectional antenna
- Other
equipment (provided by UVA)
Having gotten
both the backhaul and the initial 802.11b connection to work, we
sent out a celebratory e-mail to other participants and returned
to the boat. Unfortunately, the tide had gone out and we were stranded
a few hundred feet off Hog Island for an additional three hours.
To help redeem the time, we used a laptop computer to watch (and
listen in stereo to) streaming video of a rock concert by the alternative
group Indigenous, which
was streamed via RealPlayer at a sustained data rate of 300 kilobits
per second.
-Tom
Williams
Special Assistant
NSF Wireless Field Tests
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