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in mind as you begin to install this component. Additionally, the radios will be AC-powered
devices, and you will need to route the power cords so that they can cleanly access the power
strip that will be mounted shortly.
Chapter 9 ” Building a Solar-Powered Wireless Repeater

FIGURE 9-15: Wireless radios in place and connected via an Ethernet crossover cable.

You will clearly need to modify this step if your product is a single-board computer with inte-
grated radios, like a Soekris or open brick computer described in Chapter 8.

Products from the same manufacturer will often be designed with cases that make stacking a
cinch. Consider this fact when selecting the access point and bridge devices.

Connect the radios via an Ethernet crossover cable. Remember the configuration is for the
access point to connect back home via the wireless bridge. If the bridge is configured correctly,
the access point should believe it is sitting on the wired network back at the bottom of the
downlink. Figure 9-15 shows the radios mounted and connected.

Step 5: Install the AC Power Strip
The installation of a power strip will add enormous convenience and flexibility in your system.
Not only will it be responsible for supplying power to your critical communications devices, but
it will also give you the ability to serve any other electronic device that meets the output
requirements this system has been designed for.
For instance, you will be able to operate low power tools, temporary lighting, cell phone and
laptop chargers and any other AC-powered convenience devices that may become useful dur-
ing the installation.
226 Part III ” Playing with Access Points

Your AC Power Strip will be mounted to the top of the cabinet (see Figure 9-16). We recom-
mend attaching it the way you did all the other devices, with Velcro as the primary fastener.
Adding a third strip of Velcro to the middle of the AC Power Strip and to the corresponding
place on the cabinet back wall will add stability since this device will be subject to more strain
from plugs being inserted and removed. You are certainly welcome to use two-sided tape, but
we don™t recommend drilling holes through the exterior of the cabinet. Any water leakage in
this area could be hazardous to the equipment.
At this point, your cabinet should be fully populated. Charge the batteries by using a 12-volt
power source attached to the leads of the charge controller. Anything supporting a few
amperes at 12 V is acceptable. A car battery charger set to low-current trickle-charge works
When charging the battery, check the status lights on your charge controller. There should be a
“power on” indicator along with a “battery charging” light. When the batteries are topped off,
the “battery full” light will come on.

Do not apply more voltage or current than the charge controller is rated to handle. The controller
used in this chapter (shown earlier in Figure 9-13) is rated for 12 V and 21 A. We charged the
batteries with a 12 V, 4 A source to match the solar panel output.

FIGURE 9-16: The AC Power Strip in place and attached.
Chapter 9 ” Building a Solar-Powered Wireless Repeater

Once charged, you can remove the batteries and other components for ease of installation and
travel. As you™ve already noticed, Most of the weight in this system comes from the batteries.

Time to Go Outside
Before you head up to the installation site, one last item needs to be created, purchased, or
built: the solar panel mounting system. A solar panel mount can vary greatly in price depend-
ing on options. A high-end mount costing hundreds of dollars can be automatically or manu-
ally tilted during different seasons to account for the angle the Sun™s rays strike the panel. If
you are in low sunlight areas, an adjustable mount like this may be the best option to maximize
exposure. If you want to go crazy, robotic mounting systems can be found that track the sun as
it moves across the sky during the day.
If you happen to be in an area where sunlight is plentiful, a fixed mount is less costly and easy
to build.

Building a Mounting Bracket
You need to determine the installation angle before building a fixed-angle mount. For most
installations a tilt angle of 45 degrees is sufficient. For systems at latitudes higher than 45
degrees from the Earth™s equator, a panel tilt of 60 degrees or more is necessary.
Building a mounting system out of angle iron is cheap and easy. The structure dimensions are
shown in Figure 9-17. To accommodate the SP75 solar panel, the mount was cut into 21-inch
long angles, with 15-inch horizontal and vertical braces. The side connectors were cut in two
feet lengths.


15 in.

3 @ 24 inches
2 @ 21 inches
4 @ 15 inches
15 in.

FIGURE 9-17: Mounting structure diagram and dimensions for a 45-degree tilt.
228 Part III ” Playing with Access Points

FIGURE 9-18: A solar panel mounting structure built using angle iron.

Fortunately, the SP75 panel came with custom mounting rails designed to hold the panel down
by pressure, without the use of drilling or bolts.
The entire structure was bolted together and stands ready to accept the SP75, as shown in
Figure 9-18.

Sinking the Pole
A pole mount was chosen for this project because of high availability and low cost. Other
in-the-field mounts include guyed tower and cinder-block secured frames. These alternatives
are available from most wireless equipment distributors.
When using a basic 2-inch diameter pole, you should dig at least a 36-inch deep hole to
securely mount the pole. It will be supporting upwards of 100 pounds and in order to ensure
that it tolerates mid-range wind conditions, we strongly recommend that you cement this pole
into the ground. This will make for a sturdy and professional installation.
Select a location on the site that will offer the widest coverage area in the spots you will most
need it. For instance, you may be able to install this gear in the center of your coverage radius,
but due to terrain features or landscaping that could reduce sun hours, other spots may be more
suitable. Ensure that shade or shadows will not fall across the solar panel. Anticipate the Sun™s
angle during winter and summer months.
Chapter 9 ” Building a Solar-Powered Wireless Repeater

Once you have settled on the perfect spot, you will need to dig a hole at least 3 feet deep and
3 feet in diameter. Mix adequate amount of concrete as specified by your local hardware store
specialist and fill the hole completely. Slip the pole into the hole filled with concrete and use a
level or plumb bob to make sure that the pole is truly vertical. Wait overnight for concrete to
set before proceeding to the next step.
After sufficient time has elapsed and you are comfortable with the hardness of the concrete,
go ahead and cover up the concrete with dirt to hide the base and help restore the natural

Mounting the Equipment
The placement of all of the components on the pole is not critical, but needs to be planned for
space. The diagram in Figure 9-19 shows the components of this system and how they are
located on the pole. Place the solar panel at a height that makes it inconvenient for critters to
climb on and low enough that birds will not feel comfortable roosting for an extended time.
The goal is to minimize scratches and keep the panel as clean as possible.

At least two people should work together to mount this equipment to the pole. Safety is
paramount when working on heavy equipment. One or two people should hold the equipment
in place while another tightens down the hardware.

The equipment will be attached to the pole using U-bolts. Mount the mounting system to the
pole, leaving the solar panel to the side for the time being. You will connect the solar panel last.
When attaching the panel mount structure, ensure the panel will point due South once
attached. Use heavy-duty U-bolts to bolt the structure to the pole (see Figure 9-20).
The control cabinet is next. Remove extra components if necessary to reduce weight while mount-
ing. Keeping the batteries aside is a good idea. Removing the other components is optional.
Once again, use heavy-duty U-bolts or other appropriate fasteners to secure the cabinet in
place. Figure 9-21 shows the cabinet in place behind the panel mount structure.

Once you have completed the mounting of the Cabinet, open the door and slightly rock the
Cabinet side-to-side to verify its sturdiness.

With the cabinet installed and secured, install the batteries and attach any wiring that was
disconnected before the move.

Mounting the Antennas
The antennas should be mounted as high as possible on the pole. Direction will be determined
by the coverage area and uplink source. If possible, try to keep the antenna from casting shad-
ows over the panel. This cannot always be avoided. Select low-profile or “shadow-friendly”
230 Part III ” Playing with Access Points





Solar Mounting


FIGURE 9-19: Component mounting configuration.
Chapter 9 ” Building a Solar-Powered Wireless Repeater

FIGURE 9-20: Bolting up the panel mount structure.

FIGURE 9-21: Cabinet installed and loaded.
232 Part III ” Playing with Access Points

FIGURE 9-22: Antennas mounted to the top of the pole.

antennas if possible. For example, a parabolic grid antenna or Yagi will cast less of a shadow as
compared to a panel antenna.
U-bolts will be used to fasten the antennas to the pole. Some antennas use articulating mounts
for angle adjustment. Other antennas may have built-in electrical down-tilt. Check the specifi-
cations for your antennas and mount them as needed.
When mounting antennas for different radios as you are doing here, interference becomes a
major factor. One method of reducing radio interference is by adjusting the polarity of the sig-
nals to be 90 degrees apart. That is, set up one antenna in a vertical polarization, with the other
using a horizontal polarization. The antenna documentation will denote polarization.
In Figure 9-22, the parabolic grid antenna is vertically polarized, while this particular sector
antenna from is electrically designed for horizontal polarization (even though
it™s vertically mounted).

To further reduce interference, you can use signal filters on the antenna lines. Filters made for
specific channels of the 802.11b spectrum are available at a cost of a few hundred dollars each.

Remember to make the antenna connections water-tight. Electrical tape is a fair alternative,
but since this is a remote site, and support calls would require a special trip, the best solution is
Chapter 9 ” Building a Solar-Powered Wireless Repeater

FIGURE 9-23: Sealant tape protecting microwave connectors.

sealant tape. At ten dollars a roll, it™s not cheap, but it is the best product out there for this task.
For comparison, Figure 9-23 shows the tape in place on the top antenna connector.

Mounting the Solar Panel
The final step is to place the solar panel reverently onto the mounting structure and bolt it
down (see Figure 9-24).
Keep the panel covered with an opaque material when you™re attaching the electrical
wiring. Use a large piece of cardboard, a beach towel, or anything that covers the surface
After the panel is securely in place, attach the conduit to the junction box on the underside of
the solar panel. And connect the black wire to the negative ( ) terminal and the red wire to
the positive ( ) terminal. Do the same on the charge controller attachment points.
Follow the precautions and directions included with the solar panel you are using. The electrical
attachment points in the junction box may vary widely with each manufacturer and product.

Remember that the panel creates electricity when illuminated by sunlight. The voltage from a
single 12-volt panel is not considered a shock hazard, but to avoid sparks and possible damage,
do not short the leads while attaching the panel connections to the charge controller.
234 Part III ” Playing with Access Points

FIGURE 9-24: Solar panel installed!

Applying Power and Testing
Apply power by removing the opaque covering from the solar panel (the cardboard or beach
towel from the previous section). If it™s sunny, there should immediately be a “power on” indica-
tor and the “charging” or “full” lights will be lit. Switch on the power strip to apply AC power
to the wireless radios. Check for the usual link and status lights on your wireless equipment.

When you remove the opaque covering, the solar panel will immediately begin pumping out
electricity as fast as the sun will allow. Also, since your batteries are already charged, the radios
and inverter should be up and running even without sunshine.

With the pole securely sunk into the ground and the solar panel boldly facing the sun, it
already looks very impressive. Anyone who sees it will be very impressed with your technical
acumen and desire to improve the future of our planet.
The final stage is to move a short distance from the panel/repeater and break out your laptop
for a wireless test. Ensure that your connection is to the solar-based access point and that
your network settings match the wired network to which you are down-linking (DHCP, IP
Address, and so on).
Chapter 9 ” Building a Solar-Powered Wireless Repeater

Congratulations! You should now be surfing through your repeater. Anytime day or night, the
repeater will extend your network reach. Free and abundant daylight recharges the batteries
that ran the system overnight. The system can work perpetually over many years.
Over the years to come, you may find opportunites to expand your repeater. You may wish to
install new Wi-Fi radios or expand capabilities by installing a network camera. If your power
needs increase, the system built in this chapter can be expanded simply by adding more batter-
ies to the array. Or you may opt for a solar panel with a higher power output for quicker
recharging. Either way, the basic components of your system will serve you well into the future.

An amateur radio satellite placed into Earth orbit in 1984 is still operating after thousands of
cycles of charging and discharging on-board batteries. The satellite, named UoSat Oscar 11, cel-
ebrated its twentieth anniversary of solar-powered radio operation. May your new solar repeater
see this much uptime!

In this chapter, you learned how to set up a wireless repeater and power it with free solar
energy. You learned the background and history of photovoltaic energy, and how solar can be
used in wireless communications. With two radio repeater/bridges, you™ve extended your net-
work to the furthest reaches possible, beyond network cables, beyond telephone lines, and even
power lines. With the system you™ve installed in this chapter, you are now truly wireless.
In the next chapter, you will learn how to set up a free wireless hotspot. Read on to discover
how to create a captive portal system where wireless Internet users are automatically presented
an information screen when they open a Web browser.
Creating a Free
Wireless Hotspot
here comes a time in the life of every wireless fanatic when he or
she wants to share the thrill of wirelessness with every other human
being on the planet, or at least those who come within range.
Perhaps you have a high-speed Internet connection at home, which goes
unused when you are at work. Why not let the neighbors use it? Why not
in this chapter
let the whole neighborhood use it? And if your neighbors share with their
There are, in fact, several sizable projects underway based on this vision. As
of early 2004:
¤ NYCWireless (, dedicated to providing Setting up your
free wireless Internet service to mobile users in public spaces
network and server
throughout metropolitan New York City, had a database of over 180
nodes or hotspots.
Installing NoCat
¤ Houston Wireless (, a
community wireless group promoting pervasive, high-speed wire-
Configuring and
less data in urban and suburban Houston, was at 93 nodes and
testing NoCat
¤ Seattle Wireless network (, Troubleshooting
which envisions a not-for-profit, community-owned wireless
your access point
network covering metropolitan Seattle, had more than 30
nodes operating, and half a dozen more on the verge of
¤ The So Cal Free Net ( is rolling out
free hotspots and wireless backbone locations in the San Diego and
Los Angeles areas of Southern California.
¤ The Personal Telco Project ( consists
of a volunteer group of Portlanders with over 100 active nodes aim-
ing to cover the entire city of Portland, Oregon.
¤ The NoCat network (, based in Sebastopol
north of San Francisco, listed two-dozen active sites, almost
as many in progress, and many more that were deemed
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