The
semi-permanent tower described here is made of sturdy, pre-manufactured
materials. It is fairly simple to erect though it does require
some effort. The advantage of this tower type is that it is
fairly tall, should be able to serve an entire community,
and can be erected with little change to the environment.
The key to easily creating a semi-permanent tower such as
the one in this example, is to do as much of the work as possible
while the tower is still on the ground.
| |
Base: To
begin, create the tower base that will serve as a sturdy
mounting point for the structure. The base should be
at least 2'-0" long by 2'-0" wide by 1'-0"
deep. It should be dug into the ground, and should be
of solid concrete.
Saw some 2x8" boards to create
a form for the base, as shown. Nail the boards together
very well. Next, dig a hole large enough for the form
to fit into. The form should sit in the hole so that
the top of the form is level with the ground, however
the centre of the hole should be deeper than the form
itself, as shown.
|
Next, mix, using the instructions on the
bag, enough cement mix with water to fill the form. If there
are some large rocks around, these can be put into the hole
to save on cement, as long as there is enough cement to bind
the entire base together. (i.e. not TOO many rocks.)
Once the form is
filled, agitate the cement to ensure that it has properly
settled into the form. Next, smooth off the top nicely using
a board or a cement finishing tool.
| |
Place
the base-plate onto the wet concrete, arrange it in
the correct orientation according to the direction that
you would like the finished tower to be oriented. Note
where the bolt holes need to be. Remove the baseplate,
and push the baseplate anchorbolts into the wet concrete.
Slide the baseplate over the anchorbolts, level it in
place, wipe the tops of the anchorbolts free of any
concrete residue, and screw the nuts into place on the
anchor bolts.
Leave the form to set for the recommended
time period. If the concrete is kept wet while it is
curing, the cure will be stronger than if it is allowed
to set in completely dry conditions. Dryer conditions
during concrete setting makes a more brittle finished
product.
|
| |
Prepare
tower sections: Scrape
and sand individual tower sections and slip-up poles
as required to remove any debris. Paint all tower sections
with at least two coats of spray paint prior to assembly.
This step will ensure that the tower lasts longer, and
should be done even if the tower sections are pre-treated
(galvanized.)
|
 |
TIP:
Even if the tower sections are already
galvanized, sand and paint them with a couple
of coats of spraypaint before you put the
tower up. It will last much longer, especially
in poor weather conditions. |
|
| |
Click
here for a short film
demonstrating how
to prepare the tower
( 830 kb download). |
|
| |
Assemble
tower parts: Using a
file, remove any burrs from the metal to avoid scrapes,
then slip the tower pieces together. Bolt them firmly
into place. It is a good idea to use large eyebolts
for bolting together multi-section towers as this allows
a firm attachment point for the guywires.
The top mast generally
has a specific place where it is attached. It fits through
a triangular plate where it is affixed with a U-bolt
clamp as shown.
|
|
TIP:
Use eye bolts instead of regular bolts when
putting the tower together. This will give you a
firm, smooth attachment point for the guylines.
|
|
|
Attach
guy wires: Three guy
wires are required for every ten feet of tower height.
Each guy attachment requires two clamps, for safety
and reliability of the attachment point. This ensures
that there is no weak spot in the tower support system.
When affixing the clamps, it is best to orient them
in the opposite direction to one another. Once affixed,
tape over the end of the trimmed guywire, and both of
the clamps, with a double layer of electrical tape.
Each guy wire must
be terminated with a turnbuckle at the guyline endpoint.
Special clamps are available if guys are to be attached
to chainlink fences. This is a common practice, as
many antenna surrounds are fenced in. If a secure
mounting point such as a fence is not available, guys
may be secured by burying a deadman anchor, or a large
rock or log with a chain around it, to which the guys
may be attached.
|
| |
Assemble
tower parts: Using a
file, remove any burrs from the metal to avoid scrapes,
then slip the tower pieces together. Bolt them firmly
into place. It is a good idea to use large eyebolts
for bolting together multi-section towers as this allows
a firm attachment point for the guywires.
Next, lay out the LMR
400 waveguide cable alongside the tower in preparation
for attaching the antenna(s).
|
|
TIP:
Use TWO guywire clamps at each end. This
will eliminate weak spots. |
|
| |
Attach
Attennas to mast: Use
the clamps and fittings provided with the antenna, and
loosely attach it in its approximate final orientation.
Antennas are loosely attached at first so that they
can be easily moved around and fastened firmly only
once they are in the best orientation. If more than
one antenna is being mounted, they should be placed
at least ten feet apart. However, if both are on the
same network, this is less of an issue.
Shown being
mounted in the picture at the left are an omni directional
antenna, and a directional antenna.
Above: Omni directional antenna mounted
at the top of the mast.
Below: Covered directional
Yagi antenna mounted further down the tower mast.
|
| The omni
directional antenna is used to deliver a signal locally
within the small community where this installation is
being created, whereas the directional antenna is used
for backbone connectivity to an antenna mounted at a nearby
TV tower. |
|
|
Fasten
the antennas to the LMR 400 Waveguide: Place
a bead of silicone along the threads of the LMR 400
waveguide connector, and screw the two connector halves
together.
|
TIP:
Use a bead of silicone when screwing together
waveguide connectors - this will ensure that they
seal properly and may help the network last longer! |
Once together and tightened finger-tight,
finish tightening the connectors together, finish tightening
the connection using a wrench.
Next, wrap two layers of electrical
tape over the connection, from the bottom up, so that
water will run off the joint. See below - the taped
joint is later secured directly to the tower using tiestraps
wrapped with a layer of electrical tape as UV protection.
If more than one antenna is being
mounted, take the time at this point to carefully label
the antennas and the corresponding waveguide, using
a label machine. If a label machine is not available,
mark the antennas and waveguide clearly in another way,
(spraypaint, electrical tape around one of the antennas
and waveguides, surveyors tape, etc - whatever is handy
that will work) so that if there is a problem at some
point, it will be obvious from the ground which waveguide
belongs with which antenna.
|
Firmly
affix the wave guide to the tower: Next, tie strap
the waveguide cable along the entire length of the tower,
every 18". Also, tape well at any potential abrasion
points, such as near guy wires. Try to eliminate the possibility
for abrasion by ensuring that the waveguide is fastened
well enough that it can't come into contact with guylines
or other potentially harmful surfaces during rough weather.
If the tie-straps are attached
above the cross-members, they will not slide down. Then,
to protect the tiestraps from UV light and weather, wrap
them with a layer of electrical tape. With the tower together,
the antennas affixed and the waveguide firmly attached as
shown, the tower is now almost ready to tip up.
|
|
Affix
a danger sticker as shown prominently to the lower part
of the tower at eye level.
 Now
the tower is ready to be lifted, HOWEVER, before doing
so, stop to inspect the site.
People are killed and injured every
year trying to install towers and antennas. Take some
time to think, and make sure that you won't be one of
them.
-
Look around, remove any obstacles
that could be tripped on.
-
Check again to make sure
power lines are FAR away. Always assume that ANY overhead
lines can kill you.
Avoid overhead lines.
Period.
-
If the tower is being raised by a group of people,
assign each person a specific task, including a leader
who will co-ordinate the operation. One person should
be a spotter to watch for and warn the others of potential
problems.
-
WEAR APPROPRIATE SAFETY GEAR!!!
Hardhats, STEEL-TOED
SHOES WITH RUBBER SOLES, gloves, safety vests, long
sleeves and long pants.
-
If the tower starts
to drop, let it fall,
and GET OUT OF THE WAY!!!!
Don't try to save it. It's
a lot bigger than you are, and it's replaceable.
-
If the tower comes into contact
with an electrical wire (which it SHOULD NOT,
if the installation is correctly planned), DO
NOT TOUCH IT. Secure the area, get everyone
out of the way, and call a power crew to help.
|
|
Raising
the tower: Raise the tower slowly, using a
co-ordinated effort, with plenty of communication.
First, lift
the tower and orient it in the correct direction.
|
|
Next, have
one person hold the tower while the others untangle
or free the guywires, and make sure that the waveguide
will not be crushed while raising the tower. |
|
Lift and
guide the tower: Have one person guide the
tower base towards the base plate as the other people
lift the tower, gradually walking their hands up the
tower "ladder". |
|
Steady the
tower and bolt it down: When the base of the
tower is in place, have several people steady the
tower while one person (or two people) inserts the
bolts that will hold the tower in place.
Left: bolting the tower
in place, Right: bolting complete.
|
 |
GUY
wires: With the tower
firmly bolted in place, it is now possible to attach
the guy wires:
- Put the safety flagging over
the guy wire FIRST.
|
TIP:
If you don't have the proper safety
flagging, yellow garden hose works just as
well. |
- Next, install the clamp, deadman,
or peg to which the guyline will be attached.
- Lastly, pull the guyline through
a TURNBUCKLE, loosely
at first, then gradually tighter as all guylines
are being adjusted. Clamp
them into place using TWO clamps.
- Even up the tension on all guy
wires PRIOR to doing a final tightening on all guys.
- Cut guy wire ends to length.
- Wrap guy wire ends and clamps
with a layer of electrical tape, from the bottom
up to ensure that water will run off.
- Pull the flagging down as far
as it will come, so that it is visible near the
bottom of the guy wires where people may run into
it!
|
 |
Fasten
antennas: With the
guy wires fastened, it is now safe to climb the tower
to do the final orientation and fastening on the antennas.
- Wear a safety harness, hard
hat, and other protective gear.
- Take binoculars with you so
that you can double-check the line-of-sight if required.
- Pay attention to the polarity
of the antenna, making sure that it is installed
according to the specifications for the specific
antenna.
- Take enough tools with you,
and a crescent wrench for good measure!
- DO NOT climb the tower
if it is WINDY, RAINY, SNOWY, ICY, or if other bad
weather conditions are present which could make
you fall.
 |
If there isn't
time after installing the tower to set up
the equipment, make sure that you coil and
tape the waveguide safely in place so that
it doesn't get run over or damaged in any
way. Check to make sure that the structure
is safe before leaving it. |
|
The tower is now COMPLETE!
It's ready for you to create an equipment
enclosure, and hook
up the wireless networking equipment.
|
